Add snapshotList syntax for sequences (#25)

.envrc

@@ -1 +1,23 @@
 use flake
+DOTNET_PATH=$(readlink "$(which dotnet)")
+SETTINGS_FILE=$(find . -maxdepth 1 -type f -name '*.sln.DotSettings.user')
+MSBUILD=$(realpath "$(find "$(dirname "$DOTNET_PATH")/../share/dotnet/sdk" -maxdepth 2 -type f -name MSBuild.dll)")
+if [ -f "$SETTINGS_FILE" ] ; then
+    xmlstarlet ed --inplace \
+    -N wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation" \
+    -N x="http://schemas.microsoft.com/winfx/2006/xaml" \
+    -N s="clr-namespace:System;assembly=mscorlib" \
+    -N ss="urn:shemas-jetbrains-com:settings-storage-xaml" \
+    --update "//s:String[@x:Key='/Default/Environment/Hierarchy/Build/BuildTool/DotNetCliExePath/@EntryValue']" \
+    --value "$(realpath "$(dirname "$DOTNET_PATH")/../share/dotnet/dotnet")" \
+    "$SETTINGS_FILE"
+
+    xmlstarlet ed --inplace \
+    -N wpf="http://schemas.microsoft.com/winfx/2006/xaml/presentation" \
+    -N x="http://schemas.microsoft.com/winfx/2006/xaml" \
+    -N s="clr-namespace:System;assembly=mscorlib" \
+    -N ss="urn:shemas-jetbrains-com:settings-storage-xaml" \
+    --update "//s:String[@x:Key='/Default/Environment/Hierarchy/Build/BuildTool/CustomBuildToolPath/@EntryValue']" \
+    --value "$MSBUILD" \
+    "$SETTINGS_FILE"
+fi

README.md

@@ -16,8 +16,7 @@ An [expect-testing](https://blog.janestreet.com/the-joy-of-expect-tests/) librar
 # Current status
 
 The basic mechanism works.
-Snapshot updating is vibe-coded with Opus 4 and is purely text-based; I didn't want to use the F# compiler services because that's a pretty heavyweight dependency which should be confined to a separate test runner entity.
-It's not very well tested, and I expect it to be kind of brittle.
+It's fairly well tested, but you will almost certainly be able to find ways to break it; try not to be too fancy with your syntax around the `snapshot` statement.
 
 # How to use
 
@@ -44,8 +43,24 @@ let ``This test fails: plain text comparison of ToString`` () =
         snapshot "  123  "
         return 123
     }
+
+[<Test>]
+let ``With return! and snapshotThrows, you can see exceptions too`` () =
+    expect {
+        snapshotThrows @"System.Exception: oh no"
+        return! (fun () -> failwith<int> "oh no")
+    }
+
+[<Test>]
+let ``You can do lists more neatly with the snapshotList keyword`` () =
+    expect {
+        snapshotList [ "8" ; "9" ; "10" ; "11" ; "12" ]
+        return [ 8..12 ]
+    }
 ```
 
+(JSON output for elements is not yet supported with `snapshotList`.)
+
 You can adjust the formatting:
 
 ```fsharp
@@ -57,6 +72,15 @@ let ``Overriding the formatting`` () =
         snapshot @"Int32"
         return 123
     }
+
+[<Test>]
+let ``Overriding the formatting with lists`` () =
+    expect {
+        // these two lines *do* have to be in this order, for annoying reasons
+        snapshotList [ "8" ; "9" ; "0" ; "1" ; "2" ]
+        withFormat (fun x -> string<int> (x % 10))
+        return [ 8..12 ]
+    }
 ```
 
 You can override the JSON serialisation if you find the snapshot format displeasing:
@@ -180,6 +204,11 @@ Observe the `OneTimeSetUp` which sets global state to enter "bulk update" mode,
 
 * The snapshot updating mechanism *requires* you to use verbatim string literals. While the test assertions will work correctly if you do `snapshot ("foo" + "bar" + f 3)`, for example, the updating code is liable to do something undefined in that case. Also do not use format strings (`$"blah"`).
 
+# Output formats
+
+* The `Diff` module provides a Patience diff and a Myers diff implementation, which you can use to make certain tests much more readable.
+* The `Dot` module provides `render`, which renders a dot file as ASCII art. You will need `graph-easy` to use this feature.
+
 # Licence
 
 MIT.

WoofWare.Expect.Test/SimpleTest.fs

@@ -19,12 +19,9 @@ module SimpleTest =
     let ``Example of a failing test`` () =
         expect {
             snapshot
-                @"snapshot mismatch! snapshot at filepath.fs:99 (Example of a failing test) was:
+                @"snapshot mismatch! snapshot at filepath.fs:99 (Example of a failing test) diff:
 
 - 123
-
-actual was:
-
 + 124"
 
             return
@@ -64,26 +61,21 @@ actual was:
         // Out of the box, comments in snapshots cause the JSON parser to throw, so the snapshot fails to match...
         expect {
             snapshot
-                @"snapshot mismatch! snapshot at file.fs:99 (Custom JSON output) was:
+                @"snapshot mismatch! snapshot at file.fs:99 (Custom JSON output) diff:
 
 - [JSON failed to parse:] {
--     // a key here
--     ""a"":3
-- }
-
-actual was:
-
+-   // a key here
 + {
-+   ""a"": 3
-+ }"
+    ""a"": 3
+  }"
 
             return
                 Assert.Throws<ExpectException> (fun () ->
                     expectWithMockedFilePath ("file.fs", 99) {
                         snapshotJson
                             @"{
-    // a key here
-    ""a"":3
+  // a key here
+  ""a"": 3
 }"
 
                         return Map.ofList [ "a", 3 ]

WoofWare.Expect.Test/TestDiff.fs

@@ -0,0 +1,110 @@
+namespace WoofWare.Expect.Test
+
+open WoofWare.Expect
+open NUnit.Framework
+
+[<TestFixture>]
+module TestDiff =
+
+    [<Test>]
+    let ``Basic diff`` () =
+        let textA =
+            [|
+                "The quick brown fox"
+                "jumps over"
+                "the lazy dog"
+                "Some unique line here"
+                "The end"
+            |]
+
+        let textB =
+            [|
+                "The quick brown fox"
+                "Some unique line here"
+                "jumps over"
+                "the lazy dog"
+                "Another line"
+                "The end"
+            |]
+
+        let diff = Diff.patienceLines textA textB
+
+        expect {
+            snapshot
+                @"    0   0  The quick brown fox
++       1  Some unique line here
+    1   2  jumps over
+    2   3  the lazy dog
+-   3      Some unique line here
++       4  Another line
+    4   5  The end"
+
+            withFormat Diff.formatWithLineNumbers
+            return diff
+        }
+
+        expect {
+            snapshot
+                @"  The quick brown fox
++ Some unique line here
+  jumps over
+  the lazy dog
+- Some unique line here
++ Another line
+  The end"
+
+            withFormat Diff.format
+            return diff
+        }
+
+    [<Test>]
+    let ``An example from Incremental`` () =
+        let textA =
+            """digraph G {
+  rankdir = TB
+  bgcolor = transparent
+    n4 [shape=Mrecord label="{{n4|BindMain|height=2}}"  "fontname"="Sans Serif"]
+    n3 [shape=Mrecord label="{{n3|BindLhsChange|height=1}}"  "fontname"="Sans Serif"]
+    n1 [shape=Mrecord label="{{n1|Const|height=0}}"  "fontname"="Sans Serif"]
+    n2 [shape=Mrecord label="{{n2|Const|height=0}}"  "fontname"="Sans Serif"]
+  n3 -> n4
+  n2 -> n4
+  n1 -> n3
+}"""
+
+        let textB =
+            """digraph G {
+  rankdir = TB
+  bgcolor = transparent
+    n4 [shape=box label="{{n4|BindMain|height=2}}" ]
+    n3 [shape=box label="{{n3|BindLhsChange|height=1}}" ]
+    n1 [shape=box label="{{n1|Const|height=0}}" ]
+    n2 [shape=box label="{{n2|Const|height=0}}" ]
+  n3 -> n4
+  n2 -> n4
+  n1 -> n3
+}"""
+
+        let diff = Diff.patience textA textB
+
+        expect {
+            snapshot
+                @"  digraph G {
+    rankdir = TB
+    bgcolor = transparent
+-     n4 [shape=Mrecord label=""{{n4|BindMain|height=2}}""  ""fontname""=""Sans Serif""]
+-     n3 [shape=Mrecord label=""{{n3|BindLhsChange|height=1}}""  ""fontname""=""Sans Serif""]
+-     n1 [shape=Mrecord label=""{{n1|Const|height=0}}""  ""fontname""=""Sans Serif""]
+-     n2 [shape=Mrecord label=""{{n2|Const|height=0}}""  ""fontname""=""Sans Serif""]
++     n4 [shape=box label=""{{n4|BindMain|height=2}}"" ]
++     n3 [shape=box label=""{{n3|BindLhsChange|height=1}}"" ]
++     n1 [shape=box label=""{{n1|Const|height=0}}"" ]
++     n2 [shape=box label=""{{n2|Const|height=0}}"" ]
+    n3 -> n4
+    n2 -> n4
+    n1 -> n3
+  }"
+
+            withFormat Diff.format
+            return diff
+        }

WoofWare.Expect.Test/TestDot.fs

@@ -0,0 +1,110 @@
+namespace WoofWare.Expect.Test
+
+#nowarn 0044 // This construct is deprecated
+
+open System
+open FsUnitTyped
+open WoofWare.Expect
+open NUnit.Framework
+open System.IO.Abstractions
+open System.IO.Abstractions.TestingHelpers
+
+[<TestFixture>]
+module TestDot =
+    let toFs (fs : IFileSystem) : Dot.IFileSystem =
+        { new Dot.IFileSystem with
+            member _.DeleteFile s = fs.File.Delete s
+            member _.WriteFile path contents = fs.File.WriteAllText (path, contents)
+            member _.GetTempFileName () = fs.Path.GetTempFileName ()
+        }
+
+    [<Test ; Explicit "requires graph-easy dependency">]
+    let ``Basic dotfile, real graph-easy`` () =
+        let s =
+            """digraph G {
+  rankdir = TB
+  bgcolor = transparent
+    n2 [shape=box label="{{n2|Map|height=1}}" ]
+    n1 [shape=box label="{{n1|Const|height=0}}" ]
+  n1 -> n2
+}"""
+
+        expect {
+            snapshot
+                @"
+┌───────────────────────┐
+│ {{n1|Const|height=0}} │
+└───────────────────────┘
+  │
+  │
+  ▼
+┌───────────────────────┐
+│  {{n2|Map|height=1}}  │
+└───────────────────────┘
+"
+
+            return Dot.render s
+        }
+
+    [<Test>]
+    let ``Basic dotfile`` () =
+        let fs = MockFileSystem ()
+
+        let contents =
+            """digraph G {
+  rankdir = TB
+  bgcolor = transparent
+    n2 [shape=box label="{{n2|Map|height=1}}" ]
+    n1 [shape=box label="{{n1|Const|height=0}}" ]
+  n1 -> n2
+}"""
+
+        let mutable started = false
+        let mutable waited = false
+        let mutable exitCodeObserved = false
+        let mutable disposed = false
+
+        let expected =
+            "┌───────────────────────┐
+│ {{n1|Const|height=0}} │
+└───────────────────────┘
+  │
+  │
+  ▼
+┌───────────────────────┐
+│  {{n2|Map|height=1}}  │
+└───────────────────────┘
+"
+
+        let pr =
+            { new Dot.IProcess<IDisposable> with
+                member _.Start _ =
+                    started <- true
+                    true
+
+                member _.Create exe args =
+                    exe |> shouldEqual "graph-easy"
+
+                    args.StartsWith ("--as=boxart --from=dot ", StringComparison.Ordinal)
+                    |> shouldEqual true
+
+                    { new IDisposable with
+                        member _.Dispose () = disposed <- true
+                    }
+
+                member _.WaitForExit p = waited <- true
+                member _.ReadStandardOutput _ = expected
+
+                member _.ExitCode _ =
+                    exitCodeObserved <- true
+                    0
+            }
+
+        Dot.render' pr (toFs fs) "graph-easy" contents
+        |> _.TrimStart()
+        |> shouldEqual expected
+
+        started |> shouldEqual true
+        waited |> shouldEqual true
+        exitCodeObserved |> shouldEqual true
+        disposed |> shouldEqual true

WoofWare.Expect.Test/TestExceptionThrowing.fs

@@ -0,0 +1,14 @@
+namespace WoofWare.Expect.Test
+
+open NUnit.Framework
+open WoofWare.Expect
+
+[<TestFixture>]
+module TestExceptionThrowing =
+
+    [<Test>]
+    let ``Can throw an exception`` () =
+        expect {
+            snapshotThrows @"System.Exception: oh no"
+            return! (fun () -> failwith<int> "oh no")
+        }

WoofWare.Expect.Test/TestSnapshotFinding/TestCommentsAndSpacing.fs

@@ -34,7 +34,7 @@ module MyModule =
         expect {
             snapshot (* first comment *) (* second comment *)
                 (* third comment on new line *)
-                @""updated after many comments""
+                ""updated after many comments""
 
             return 123
         }
@@ -100,7 +100,7 @@ module MyModule =
 
     let nestedComments () =
         expect {
-            snapshot (* outer (* inner *) comment *) @""updated after nested comments""
+            snapshot (* outer (* inner *) comment *) ""updated after nested comments""
             return ""nested""
         }
 
@@ -165,7 +165,7 @@ module MyModule =
 
     let commentWithSpecialChars () =
         expect {
-            snapshot (* comment with ""quotes"" and \ backslash *) @""updated after weird comment""
+            snapshot (* comment with ""quotes"" and \ backslash *) ""updated after weird comment""
             return ""special""
         }
 
@@ -233,7 +233,7 @@ module MyModule =
             snapshot
 
 
-                @""updated after spaces""
+                ""updated after spaces""
 
             return ""whitespace""
         }
@@ -301,7 +301,7 @@ module MyModule =
         expect {
             snapshotJson (* comment 1 *)
                 (* comment 2 *)
-                (* comment 3 *) @""updated after comments""
+                (* comment 3 *) ""updated after comments""
 
             return 123
         }

WoofWare.Expect.Test/TestSnapshotFinding/TestEdgeCases.fs

@@ -31,7 +31,7 @@ open WoofWare.Expect
 module MyModule =
     let emptyString () =
         expect {
-            snapshot @""now has content""
+            snapshot ""now has content""
             return """"
         }
 
@@ -121,7 +121,7 @@ module MyModule =
 
     let emptyVerbatim () =
         expect {
-            snapshot @""now has content""
+            snapshot ""now has content""
             return """"
         }
 
@@ -211,7 +211,7 @@ module MyModule =
 
     let emptyTripleQuote () =
         expect {
-            snapshot @""now has content""
+            snapshot ""now has content""
             return """"
         }
 
@@ -301,7 +301,7 @@ module MyModule =
 
     let onlyWhitespace () =
         expect {
-            snapshot @""now has content""
+            snapshot ""now has content""
             return ""whitespace""
         }
 
@@ -575,7 +575,7 @@ module MyModule =
     let veryLongLine () =
         expect {
             snapshot
-                @""this line is short though""
+                ""this line is short though""
 
             return ""long line""
         }

WoofWare.Expect.Test/TestSnapshotFinding/TestMultilineComplex.fs

@@ -472,7 +472,7 @@ Sixth line""
 
     let windowsLineEndings () =
         expect {
-            snapshot @""down with line endings""
+            snapshot ""down with line endings""
             return ""crlf""
         }
 "

WoofWare.Expect.Test/TestSnapshotFinding/TestSnapshotFinding.fs

@@ -32,7 +32,7 @@ open WoofWare.Expect
 module MyModule =
     let foo () =
         expect {
-            snapshot @""replacement""
+            snapshot ""replacement""
             return 123
         }
 "
@@ -81,7 +81,7 @@ open WoofWare.Expect
 module MyModule =
     let foo () =
         expect {
-            snapshot @""replacement""
+            snapshot ""replacement""
             return 123
         }
 "

WoofWare.Expect.Test/TestSnapshotFinding/TestUnicodeCharacters.fs

@@ -31,7 +31,7 @@ open WoofWare.Expect
 module MyModule =
     let emoji () =
         expect {
-            snapshot @""Updated with 🚀🌟✨ more emoji!""
+            snapshot ""Updated with 🚀🌟✨ more emoji!""
             return 123
         }
 
@@ -172,7 +172,7 @@ module MyModule =
 
     let arabicRTL () =
         expect {
-            snapshot @""Updated Arabic: مرحبا بالعالم""
+            snapshot ""Updated Arabic: مرحبا بالعالم""
             return ""rtl test""
         }
 
@@ -241,7 +241,7 @@ module MyModule =
     let combiningCharacters () =
         expect {
             // Combining diacritics: e + ́ = é
-            snapshot @""updated test with combining: é and ä!""
+            snapshot ""updated test with combining: é and ä!""
             return ""combining""
         }
 
@@ -309,7 +309,7 @@ module MyModule =
 
     let mixedScripts () =
         expect {
-            snapshotJson @""Updated mixed: English, русский, 日本語, العربية, emoji 🚀""
+            snapshotJson ""Updated mixed: English, русский, 日本語, العربية, emoji 🚀""
             return [ ""multilingual"" ]
         }
 
@@ -377,7 +377,7 @@ module MyModule =
 
     let zeroWidthChars () =
         expect {
-            snapshot @""Updated: Zero​width​space​test"" // Contains U+200B
+            snapshot ""Updated: Zero​width​space​test"" // Contains U+200B
             return ""zwsp""
         }
 
@@ -445,7 +445,7 @@ module MyModule =
 
     let mathSymbols () =
         expect {
-            snapshot @""Pretty vacuous, huh: ∀x∈ℝ, ∃y: x² + y² = 1 ⟹ |x| ≤ 1""
+            snapshot ""Pretty vacuous, huh: ∀x∈ℝ, ∃y: x² + y² = 1 ⟹ |x| ≤ 1""
             return ""math""
         }
 "

WoofWare.Expect.Test/TestSnapshotList.fs

@@ -0,0 +1,32 @@
+namespace WoofWare.Expect.Test
+
+open NUnit.Framework
+open WoofWare.Expect
+
+[<TestFixture>]
+module TestSnapshotList =
+    [<OneTimeSetUp>]
+    let ``Prepare to bulk-update tests`` () =
+        // If you don't want to enter bulk-update mode, just replace this line with a no-op `()`.
+        // The `updateAllSnapshots` tear-down below will simply do nothing in that case.
+        // GlobalBuilderConfig.enterBulkUpdateMode ()
+        ()
+
+    [<OneTimeTearDown>]
+    let ``Update all tests`` () =
+        GlobalBuilderConfig.updateAllSnapshots ()
+
+    [<Test>]
+    let ``simple list test`` () =
+        expect {
+            snapshotList [ "1" ; "2" ; "3" ]
+            return [ 1..3 ]
+        }
+
+    [<Test>]
+    let ``list test with formatting`` () =
+        expect {
+            snapshotList [ "8" ; "9" ; "0" ; "1" ; "2" ]
+            withFormat (fun x -> string<int> (x % 10))
+            return [ 8..12 ]
+        }

WoofWare.Expect.Test/WoofWare.Expect.Test.fsproj

@@ -13,6 +13,10 @@
       <Compile Include="Assembly.fs" />
       <Compile Include="BulkUpdateExample.fs" />
       <Compile Include="SimpleTest.fs" />
+      <Compile Include="TestDiff.fs" />
+      <Compile Include="TestDot.fs" />
+      <Compile Include="TestExceptionThrowing.fs" />
+      <Compile Include="TestSnapshotList.fs" />
       <Compile Include="TestSurface.fs" />
       <Compile Include="TestSnapshotFinding\TestSnapshotFinding.fs" />
       <Compile Include="TestSnapshotFinding\TestUnicodeCharacters.fs" />
@@ -38,6 +42,9 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1"/>
         <PackageReference Include="NUnit" Version="4.3.2"/>
         <PackageReference Include="NUnit3TestAdapter" Version="5.0.0"/>
+      <!-- TODO: when ApiSurface accepts https://github.com/G-Research/ApiSurface/pull/116, upgrade these -->
+        <PackageReference Include="System.IO.Abstractions" Version="4.2.13" />
+        <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="4.2.13" />
     </ItemGroup>
 
     <ItemGroup>

WoofWare.Expect/AstWalker.fs

@@ -0,0 +1,213 @@
+namespace WoofWare.Expect
+
+// This file mostly courtesy of Claude 4 Opus.
+
+open Fantomas.FCS.Diagnostics
+open Fantomas.FCS.Syntax
+open Fantomas.FCS.Text
+
+type internal SnapshotLocation =
+    {
+        KeywordRange : Range
+        Keyword : string
+        ReplacementRange : Range
+    }
+
+[<RequireQualifiedAccess>]
+module internal AstWalker =
+
+    let private snapshotSignifier =
+        [ "snapshot" ; "snapshotJson" ; "snapshotList" ; "snapshotThrows" ]
+        |> Set.ofList
+
+    /// Check if this is a call to snapshotList (or any other snapshot method we care about)
+    /// Returns the identifier that is the snapshot invocation, and its range.
+    let private isSnapshotCall (funcExpr : SynExpr) : (string * Range) option =
+        match funcExpr with
+        | SynExpr.Ident ident when snapshotSignifier.Contains ident.idText -> Some (ident.idText, ident.idRange)
+        | SynExpr.LongIdent (_, longIdent, _, _) ->
+            match longIdent.IdentsWithTrivia with
+            | [] -> None
+            | ids ->
+                match List.last ids with
+                | SynIdent.SynIdent (ident, _) ->
+                    if snapshotSignifier.Contains ident.idText then
+                        Some (ident.idText, ident.idRange)
+                    else
+                        None
+        | _ -> None
+
+    /// Extract the argument from a method application
+    let private getMethodArgument (expr : SynExpr) =
+        match expr with
+        | SynExpr.App (_, _, _, argExpr, _) -> Some argExpr
+        | _ -> None
+
+    /// Walk expressions looking for our target
+    let rec findSnapshotListCalls (targetLine : int) (methodName : string) (expr : SynExpr) : SnapshotLocation list =
+        match expr with
+        // Direct method application
+        | SynExpr.App (_, _, funcExpr, argExpr, range) ->
+            match isSnapshotCall funcExpr with
+            | Some (keyword, keywordRange) ->
+                if range.StartLine <= targetLine && targetLine <= range.EndLine then
+                    match argExpr with
+                    | SynExpr.ArrayOrList (isList, _, argRange) when isList ->
+                        // It's a list literal
+                        [
+                            {
+                                ReplacementRange = argRange
+                                KeywordRange = keywordRange
+                                Keyword = keyword
+                            }
+                        ] // Text will be extracted separately
+                    | SynExpr.ArrayOrListComputed (isArray, _inner, argRange) when not isArray ->
+                        // It's a list comprehension
+                        [
+                            {
+                                ReplacementRange = argRange
+                                KeywordRange = keywordRange
+                                Keyword = keyword
+                            }
+                        ]
+                    | _ ->
+                        // It could be a variable reference or other expression
+                        [
+                            {
+                                ReplacementRange = argExpr.Range
+                                KeywordRange = keywordRange
+                                Keyword = keyword
+                            }
+                        ]
+                else
+                    []
+            | None ->
+                // Other app variations
+                findSnapshotListCalls targetLine methodName funcExpr
+                @ findSnapshotListCalls targetLine methodName argExpr
+
+        // Nested in paren
+        | SynExpr.Paren (innerExpr, _, _, _) -> findSnapshotListCalls targetLine methodName innerExpr
+
+        // Sequential expressions (e.g., in a do block)
+        | SynExpr.Sequential (_, _, expr1, expr2, _, _) ->
+            findSnapshotListCalls targetLine methodName expr1
+            @ findSnapshotListCalls targetLine methodName expr2
+
+        // Let bindings
+        | SynExpr.LetOrUse (_, _, bindings, bodyExpr, _, _) ->
+            let bindingResults =
+                bindings
+                |> List.collect (fun binding ->
+                    match binding with
+                    | SynBinding (expr = expr) -> findSnapshotListCalls targetLine methodName expr
+                )
+
+            bindingResults @ findSnapshotListCalls targetLine methodName bodyExpr
+
+        // Match expressions
+        | SynExpr.Match (_, _, clauses, _, _) ->
+            clauses
+            |> List.collect (fun (SynMatchClause (resultExpr = expr)) ->
+                findSnapshotListCalls targetLine methodName expr
+            )
+
+        // If/then/else
+        | SynExpr.IfThenElse (_, thenExpr, elseExprOpt, _, _, _, _) ->
+            let thenResults = findSnapshotListCalls targetLine methodName thenExpr
+
+            let elseResults =
+                match elseExprOpt with
+                | Some elseExpr -> findSnapshotListCalls targetLine methodName elseExpr
+                | None -> []
+
+            thenResults @ elseResults
+
+        // Lambda
+        | SynExpr.Lambda (body = bodyExpr) -> findSnapshotListCalls targetLine methodName bodyExpr
+
+        // Computation expression
+        | SynExpr.ComputationExpr (_, innerExpr, _) -> findSnapshotListCalls targetLine methodName innerExpr
+
+        // Default case - no results
+        | _ -> []
+
+    /// Walk a module or namespace looking for expressions
+    let rec findInModuleDecls (targetLine : int) (methodName : string) (decls : SynModuleDecl list) =
+        decls
+        |> List.collect (fun decl ->
+            match decl with
+            | SynModuleDecl.Let (_, bindings, _) ->
+                bindings
+                |> List.collect (fun binding ->
+                    match binding with
+                    | SynBinding (expr = expr) -> findSnapshotListCalls targetLine methodName expr
+                )
+
+            | SynModuleDecl.Expr (expr, _) -> findSnapshotListCalls targetLine methodName expr
+
+            | SynModuleDecl.NestedModule (decls = nestedDecls) -> findInModuleDecls targetLine methodName nestedDecls
+
+            | SynModuleDecl.Types (typeDefs, _) ->
+                typeDefs
+                |> List.collect (fun typeDef ->
+                    match typeDef with
+                    | SynTypeDefn (typeRepr = SynTypeDefnRepr.ObjectModel (members = members)) ->
+                        members
+                        |> List.collect (fun member' ->
+                            match member' with
+                            | SynMemberDefn.Member (memberBinding, _) ->
+                                match memberBinding with
+                                | SynBinding (expr = expr) -> findSnapshotListCalls targetLine methodName expr
+                            | _ -> []
+                        )
+                    | _ -> []
+                )
+
+            | SynModuleDecl.HashDirective _
+            | SynModuleDecl.Attributes _
+            | SynModuleDecl.ModuleAbbrev _
+            | SynModuleDecl.Exception _
+            | SynModuleDecl.Open _ -> []
+            | SynModuleDecl.NamespaceFragment (SynModuleOrNamespace (decls = decls)) ->
+                findInModuleDecls targetLine methodName decls
+        )
+
+    /// Main function to find snapshot list locations
+    let findSnapshotList
+        (infoFilePath : string)
+        (lines : string[])
+        (lineNumber : int)
+        (methodName : string) // e.g., "snapshotList"
+        : SnapshotLocation
+        =
+        let sourceText = SourceText.ofString (String.concat "\n" lines)
+
+        // Parse the file
+        let parsedInput, diagnostics = Fantomas.FCS.Parse.parseFile false sourceText []
+
+        // Check for parse errors
+        if
+            diagnostics
+            |> List.exists (fun d -> d.Severity = FSharpDiagnosticSeverity.Error)
+        then
+            failwithf $"Parse errors in file %s{infoFilePath}: %A{diagnostics}"
+
+        // Walk the AST
+        let results =
+            match parsedInput with
+            | ParsedInput.ImplFile (ParsedImplFileInput (contents = modules)) ->
+                modules
+                |> List.collect (fun moduleOrNs ->
+                    match moduleOrNs with
+                    | SynModuleOrNamespace (decls = decls) -> findInModuleDecls lineNumber methodName decls
+                )
+            | ParsedInput.SigFile _ -> failwith "unexpected: signature files can't contain expressions"
+
+        // Find the closest match
+        results
+        |> Seq.filter (fun loc ->
+            loc.KeywordRange.StartLine <= lineNumber
+            && lineNumber <= loc.KeywordRange.EndLine
+        )
+        |> Seq.exactlyOne

WoofWare.Expect/Builder.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.Expect
 
+open System.Collections.Generic
 open System.IO
 open System.Runtime.CompilerServices
 open System.Text.Json
@@ -23,8 +24,6 @@ type Mode =
 /// <param name="applyChanges">When running the tests, instead of throwing an exception on failure, update the snapshot.</param>
 /// <param name="sourceOverride">Override the file path and line numbers reported in snapshots, so that your tests can be fully stable even on failure. (You almost certainly don't want to set this.)</param>
 type ExpectBuilder (mode : Mode) =
-    member private this.Mode = Unchecked.defaultof<Mode>
-
     new (sourceOverride : string * int) = ExpectBuilder (Mode.AssertMockingSource sourceOverride)
 
     new (update : bool)
@@ -34,6 +33,61 @@ type ExpectBuilder (mode : Mode) =
         else
             ExpectBuilder Mode.Assert
 
+    /// Combine two `ExpectStateListy`s. The first one is the "expected" snapshot; the second is the "actual".
+    member _.Bind<'U> (state : ExpectStateListy<'U>, f : unit -> ExpectStateListy<'U>) : ExpectStateListy<'U> =
+        let actual = f ()
+
+        match state.Actual with
+        | Some _ -> failwith "somehow came in with an Actual"
+        | None ->
+
+        match actual.Snapshot with
+        | Some _ -> failwith "somehow Actual came through with a Snapshot"
+        | None ->
+
+        let formatter =
+            match state.Formatter, actual.Formatter with
+            | None, f -> f
+            | Some f, None -> Some f
+            | Some _, Some _ -> failwith "multiple formatters supplied for a single expect!"
+
+        {
+            Formatter = formatter
+            Snapshot = state.Snapshot
+            Actual = actual.Actual
+        }
+
+    /// Combine an `ExpectStateListy` with an `ExpectState`. The first one is the "expected" snapshot; the second is
+    /// the "actual".
+    member _.Bind<'U, 'elt when 'U :> IEnumerable<'elt>>
+        (state : ExpectStateListy<'elt>, f : unit -> ExpectState<'U>)
+        : ExpectStateListy<'elt>
+        =
+        let actual = f ()
+
+        match state.Actual with
+        | Some _ -> failwith "somehow came in with an Actual"
+        | None ->
+
+        match actual.Snapshot with
+        | Some _ -> failwith "somehow Actual came through with a Snapshot"
+        | None ->
+
+        let formatter : ((unit -> 'elt) -> string) option =
+            match state.Formatter, actual.Formatter with
+            | None, None -> None
+            | None, Some _ ->
+                failwith
+                    "unexpectedly had a formatter supplied before the snapshotList keyword; I thought this was impossible"
+            | Some f, None -> Some f
+            | Some _, Some _ -> failwith "multiple formatters supplied for a single expect!"
+
+        {
+            Formatter = formatter
+            Snapshot = state.Snapshot
+            Actual = actual.Actual |> Option.map (fun f () -> Seq.cast<'elt> (f ()))
+        }
+
     /// Combine two `ExpectState`s. The first one is the "expected" snapshot; the second is the "actual".
     member _.Bind<'U> (state : ExpectState<'U>, f : unit -> ExpectState<'U>) : ExpectState<'U> =
         let actual = f ()
@@ -73,6 +127,40 @@ type ExpectBuilder (mode : Mode) =
             JsonDocOptions = jsonDocOptions
         }
 
+    /// <summary>Express that the actual value's <c>ToString</c> should identically equal this string.</summary>
+    [<CustomOperation("snapshot", MaintainsVariableSpaceUsingBind = true)>]
+    member _.Snapshot<'a>
+        (
+            state : ExpectStateListy<'a>,
+            snapshot : string,
+            [<CallerMemberName>] ?memberName : string,
+            [<CallerLineNumber>] ?callerLine : int,
+            [<CallerFilePath>] ?filePath : string
+        )
+        : ExpectState<'a>
+        =
+        match state.Snapshot with
+        | Some _ -> failwith "snapshot can only be specified once"
+        | None ->
+            let memberName = defaultArg memberName "<unknown method>"
+            let filePath = defaultArg filePath "<unknown file>"
+            let lineNumber = defaultArg callerLine -1
+
+            let callerInfo =
+                {
+                    MemberName = memberName
+                    FilePath = filePath
+                    LineNumber = lineNumber
+                }
+
+            {
+                Formatter = state.Formatter
+                JsonSerialiserOptions = None
+                JsonDocOptions = None
+                Snapshot = Some (SnapshotValue.Formatted snapshot, callerInfo)
+                Actual = None
+            }
+
     /// <summary>Express that the actual value's <c>ToString</c> should identically equal this string.</summary>
     [<CustomOperation("snapshot", MaintainsVariableSpaceUsingBind = true)>]
     member _.Snapshot<'a>
@@ -104,6 +192,46 @@ type ExpectBuilder (mode : Mode) =
                 Actual = None
             }
 
+    /// <summary>
+    /// Express that the actual value, when converted to JSON, should result in a JSON document
+    /// which matches the JSON document that is this string.
+    /// </summary>
+    /// <remarks>
+    /// For example, <c>snapshotJson "123"</c> indicates the JSON integer 123.
+    /// </remarks>
+    [<CustomOperation("snapshotJson", MaintainsVariableSpaceUsingBind = true)>]
+    member this.SnapshotJson<'a>
+        (
+            state : ExpectStateListy<unit>,
+            snapshot : string,
+            [<CallerMemberName>] ?memberName : string,
+            [<CallerLineNumber>] ?callerLine : int,
+            [<CallerFilePath>] ?filePath : string
+        )
+        : ExpectState<'a>
+        =
+        match state.Snapshot with
+        | Some _ -> failwith "snapshot can only be specified once"
+        | None ->
+            let memberName = defaultArg memberName "<unknown method>"
+            let filePath = defaultArg filePath "<unknown file>"
+            let lineNumber = defaultArg callerLine -1
+
+            let callerInfo =
+                {
+                    MemberName = memberName
+                    FilePath = filePath
+                    LineNumber = lineNumber
+                }
+
+            {
+                Formatter = None
+                JsonSerialiserOptions = None
+                JsonDocOptions = None
+                Snapshot = Some (SnapshotValue.Json snapshot, callerInfo)
+                Actual = None
+            }
+
     /// <summary>
     /// Express that the actual value, when converted to JSON, should result in a JSON document
     /// which matches the JSON document that is this string.
@@ -144,10 +272,138 @@ type ExpectBuilder (mode : Mode) =
                 Actual = None
             }
 
+    /// <summary>
+    /// Express that the actual value, which is a sequence, should have elements which individually (in order) match
+    /// this snapshot list.
+    /// </summary>
+    /// <remarks>
+    /// For example, <c>snapshotList ["123" ; "456"]</c> indicates an exactly-two-element list <c>[123 ; 456]</c>.
+    /// </remarks>
+    [<CustomOperation("snapshotList", MaintainsVariableSpaceUsingBind = true)>]
+    member _.SnapshotList<'a>
+        (
+            state : ExpectStateListy<unit>,
+            snapshot : string list,
+            [<CallerMemberName>] ?memberName : string,
+            [<CallerLineNumber>] ?callerLine : int,
+            [<CallerFilePath>] ?filePath : string
+        )
+        : ExpectStateListy<'a>
+        =
+
+        match state.Snapshot with
+        | Some _ -> failwith "snapshot can only be specified once"
+        | None ->
+            let memberName = defaultArg memberName "<unknown method>"
+            let filePath = defaultArg filePath "<unknown file>"
+            let lineNumber = defaultArg callerLine -1
+
+            let callerInfo =
+                {
+                    MemberName = memberName
+                    FilePath = filePath
+                    LineNumber = lineNumber
+                }
+
+            {
+                Formatter = None
+                Snapshot = Some (snapshot, callerInfo)
+                Actual = None
+            }
+
+    /// <summary>
+    /// Expresses that the given expression throws during evaluation.
+    /// </summary>
+    /// <example>
+    /// <code>
+    /// expect {
+    ///     snapshotThrows @"System.Exception: oh no"
+    ///     return! (fun () -> failwith "oh no")
+    /// }
+    /// </code>
+    /// </example>
+    [<CustomOperation("snapshotThrows", MaintainsVariableSpaceUsingBind = true)>]
+    member _.SnapshotThrows<'a>
+        (
+            state : ExpectState<'a>,
+            snapshot : string,
+            [<CallerMemberName>] ?memberName : string,
+            [<CallerLineNumber>] ?callerLine : int,
+            [<CallerFilePath>] ?filePath : string
+        )
+        : ExpectState<'a>
+        =
+        match state.Snapshot with
+        | Some _ -> failwith "snapshot can only be specified once"
+        | None ->
+
+            let memberName = defaultArg memberName "<unknown method>"
+            let filePath = defaultArg filePath "<unknown file>"
+            let lineNumber = defaultArg callerLine -1
+
+            let callerInfo =
+                {
+                    MemberName = memberName
+                    FilePath = filePath
+                    LineNumber = lineNumber
+                }
+
+            {
+                Formatter = None
+                JsonSerialiserOptions = state.JsonSerialiserOptions
+                JsonDocOptions = state.JsonDocOptions
+                Snapshot = Some (SnapshotValue.ThrowsException snapshot, callerInfo)
+                Actual = None
+            }
+
+    /// <summary>
+    /// Expresses that the given expression throws during evaluation.
+    /// </summary>
+    /// <example>
+    /// <code>
+    /// expect {
+    ///     snapshotThrows @"System.Exception: oh no"
+    ///     return! (fun () -> failwith "oh no")
+    /// }
+    /// </code>
+    /// </example>
+    [<CustomOperation("snapshotThrows", MaintainsVariableSpaceUsingBind = true)>]
+    member _.SnapshotThrows<'a>
+        (
+            state : ExpectStateListy<'a>,
+            snapshot : string,
+            [<CallerMemberName>] ?memberName : string,
+            [<CallerLineNumber>] ?callerLine : int,
+            [<CallerFilePath>] ?filePath : string
+        )
+        : ExpectState<'a>
+        =
+        match state.Snapshot with
+        | Some _ -> failwith "snapshot can only be specified once"
+        | None ->
+
+            let memberName = defaultArg memberName "<unknown method>"
+            let filePath = defaultArg filePath "<unknown file>"
+            let lineNumber = defaultArg callerLine -1
+
+            let callerInfo =
+                {
+                    MemberName = memberName
+                    FilePath = filePath
+                    LineNumber = lineNumber
+                }
+
+            {
+                Formatter = None
+                JsonSerialiserOptions = None
+                JsonDocOptions = None
+                Snapshot = Some (SnapshotValue.ThrowsException snapshot, callerInfo)
+                Actual = None
+            }
+
     /// <summary>
     /// Express that the <c>return</c> value of this builder should be formatted using this function, before
     /// comparing to the snapshot.
-    /// this value.
     /// </summary>
     /// <remarks>
     /// For example, <c>withFormat (fun x -> x.ToString ()) "123"</c> is equivalent to <c>snapshot "123"</c>.
@@ -158,7 +414,24 @@ type ExpectBuilder (mode : Mode) =
         | Some _ -> failwith "Please don't supply withFormat more than once"
         | None ->
             { state with
-                Formatter = Some formatter
+                Formatter = Some (fun f -> f () |> formatter)
+            }
+
+    /// <summary>
+    /// Express that the <c>return</c> value of this builder should be formatted using this function, before
+    /// comparing to the snapshot.
+    /// In the case of <c>snapshotList</c>, this applies to the elements of the sequence, not to the sequence itself.
+    /// </summary>
+    /// <remarks>
+    /// For example, <c>withFormat (fun x -> x.ToString ()) "123"</c> is equivalent to <c>snapshot "123"</c>.
+    /// </remarks>
+    [<CustomOperation("withFormat", MaintainsVariableSpaceUsingBind = true)>]
+    member _.WithFormat<'T> (state : ExpectStateListy<'T>, formatter : 'T -> string) =
+        match state.Formatter with
+        | Some _ -> failwith "Please don't supply withFormat more than once"
+        | None ->
+            { state with
+                Formatter = Some (fun f -> f () |> formatter)
             }
 
     /// <summary>
@@ -184,6 +457,42 @@ type ExpectBuilder (mode : Mode) =
                 JsonSerialiserOptions = Some jsonOptions
             }
 
+    /// <summary>
+    /// Express that these JsonSerializerOptions should be used to construct the JSON object to which the snapshot
+    /// is to be compared (or, in write-out-the-snapshot mode, to construct the JSON object to be written out).
+    /// </summary>
+    /// <example>
+    /// If you want your snapshots to be written out compactly, rather than the default indenting:
+    /// <code>
+    /// expect {
+    ///     snapshotJson @"{""a"":3}"
+    ///     withJsonSerializerOptions (JsonSerializerOptions (WriteIndented = false))
+    ///     return Map.ofList ["a", 3]
+    /// }
+    /// </code>
+    /// </example>
+    [<CustomOperation("withJsonSerializerOptions", MaintainsVariableSpaceUsingBind = true)>]
+    member _.WithJsonSerializerOptions<'T> (state : ExpectStateListy<'T>, jsonOptions : JsonSerializerOptions) =
+        match state.Snapshot with
+        | Some _ ->
+            failwith
+                "I don't know how you've managed to do this; please raise an issue against github.com/Smaug123/WoofWare.Expect . Somehow withJsonSerializerOptions has already got a snapshot."
+        | None ->
+
+        match state.Actual with
+        | Some _ ->
+            failwith
+                "I don't know how you've managed to do this; please raise an issue against github.com/Smaug123/WoofWare.Expect . Somehow withJsonSerializerOptions has already got an expected-value."
+        | None ->
+
+        {
+            Formatter = state.Formatter
+            JsonSerialiserOptions = Some jsonOptions
+            JsonDocOptions = None
+            Snapshot = None
+            Actual = None
+        }
+
     /// <summary>
     /// Express that these JsonDocumentOptions should be used when parsing the snapshot string into a JSON object.
     /// </summary>
@@ -215,17 +524,26 @@ type ExpectBuilder (mode : Mode) =
             }
 
     /// MaintainsVariableSpaceUsingBind causes this to be used; it's a dummy representing "no snapshot and no assertion".
-    member _.Return (() : unit) : ExpectState<'T> =
+    member _.Return (() : unit) : ExpectStateListy<'T> =
         {
             Formatter = None
-            JsonSerialiserOptions = None
-            JsonDocOptions = None
             Snapshot = None
             Actual = None
         }
 
     /// Expresses the "actual value" component of the assertion "expected snapshot = actual value".
-    member _.Return (value : 'T) : ExpectState<'T> =
+    member _.Return<'T> (value : 'T) : ExpectState<'T> =
+        {
+            Snapshot = None
+            Formatter = None
+            Actual = Some (fun () -> value)
+            JsonSerialiserOptions = None
+            JsonDocOptions = None
+        }
+
+    /// Expresses the "actual value" component of the assertion "expected snapshot = actual value", but delayed behind
+    /// a function (by contrast with `Return`).
+    member _.ReturnFrom (value : unit -> 'T) : ExpectState<'T> =
         {
             Snapshot = None
             Formatter = None
@@ -237,6 +555,56 @@ type ExpectBuilder (mode : Mode) =
     /// Computation expression `Delay`.
     member _.Delay (f : unit -> ExpectState<'T>) : unit -> ExpectState<'T> = f
 
+    /// Computation expression `Delay`.
+    member _.Delay (f : unit -> ExpectStateListy<'T>) : unit -> ExpectStateListy<'T> = f
+
+    /// Computation expression `Run`, which runs a `Delay`ed snapshot assertion, throwing if the assertion fails.
+    member _.Run (f : unit -> ExpectStateListy<'T>) : unit =
+        let state = f () |> CompletedListSnapshotGeneric.make
+
+        let lines = lazy File.ReadAllLines state.Caller.FilePath
+
+        let listSource =
+            lazy
+                AstWalker.findSnapshotList
+                    state.Caller.FilePath
+                    (lines.Force ())
+                    state.Caller.LineNumber
+                    state.Caller.MemberName
+
+        let raiseError expected actual =
+            let diff =
+                Diff.patienceLines (Array.ofList expected) (Array.ofList actual) |> Diff.format
+
+            match mode with
+            | Mode.Assert ->
+                if GlobalBuilderConfig.isBulkUpdateMode () then
+                    GlobalBuilderConfig.registerTest (CompletedSnapshot.makeFromAst (listSource.Force ()) state)
+                else
+                    $"snapshot mismatch! snapshot at %s{state.Caller.FilePath}:%i{state.Caller.LineNumber} (%s{state.Caller.MemberName}) diff:\n%s{diff}"
+                    |> ExpectException
+                    |> raise
+            | Mode.AssertMockingSource (mockSource, line) ->
+                $"snapshot mismatch! snapshot at %s{mockSource}:%i{line} (%s{state.Caller.MemberName}) diff:\n%s{diff}"
+                |> ExpectException
+                |> raise
+            | Mode.Update ->
+                let lines = lines.Force ()
+                let listSource = listSource.Force ()
+                let result = SnapshotUpdate.updateAtLocation listSource lines actual
+                File.writeAllLines result state.Caller.FilePath
+                failwith ("Snapshot successfully updated. Previous contents:\n" + String.concat "\n" lines)
+
+        match CompletedListSnapshotGeneric.passesAssertion state with
+        | None ->
+            match mode, GlobalBuilderConfig.isBulkUpdateMode () with
+            | Mode.Update, _
+            | _, true ->
+                failwith
+                    "Snapshot assertion passed, but we are in snapshot-updating mode. Use the `expect` builder instead of `expect'` to assert the contents of a single snapshot; disable `GlobalBuilderConfig.bulkUpdate` to move back to assertion-checking mode."
+            | _ -> ()
+        | Some (expected, actual) -> raiseError expected actual
+
     /// Computation expression `Run`, which runs a `Delay`ed snapshot assertion, throwing if the assertion fails.
     member _.Run (f : unit -> ExpectState<'T>) : unit =
         let state = f () |> CompletedSnapshotGeneric.make
@@ -244,40 +612,42 @@ type ExpectBuilder (mode : Mode) =
         let raiseError (snapshot : string) (actual : string) : unit =
             match mode with
             | Mode.AssertMockingSource (mockSource, line) ->
+                let diff = Diff.patience snapshot actual
+
                 sprintf
-                    "snapshot mismatch! snapshot at %s:%i (%s) was:\n\n%s\n\nactual was:\n\n%s"
+                    "snapshot mismatch! snapshot at %s:%i (%s) diff:\n\n%s"
                     mockSource
                     line
                     state.Caller.MemberName
-                    (snapshot |> Text.predent '-')
-                    (actual |> Text.predent '+')
+                    (Diff.format diff)
                 |> ExpectException
                 |> raise
             | Mode.Assert ->
-                if GlobalBuilderConfig.bulkUpdate.Value > 0 then
-                    GlobalBuilderConfig.registerTest state
+                if GlobalBuilderConfig.isBulkUpdateMode () then
+                    GlobalBuilderConfig.registerTest (CompletedSnapshot.makeGuess state)
                 else
+                    let diff = Diff.patience snapshot actual
+
                     sprintf
-                        "snapshot mismatch! snapshot at %s:%i (%s) was:\n\n%s\n\nactual was:\n\n%s"
+                        "snapshot mismatch! snapshot at %s:%i (%s) diff:\n\n%s"
                         state.Caller.FilePath
                         state.Caller.LineNumber
                         state.Caller.MemberName
-                        (snapshot |> Text.predent '-')
-                        (actual |> Text.predent '+')
+                        (Diff.format diff)
                     |> ExpectException
                     |> raise
             | Mode.Update ->
                 let lines = File.ReadAllLines state.Caller.FilePath
                 let oldContents = String.concat "\n" lines
                 let lines = SnapshotUpdate.updateSnapshotAtLine lines state.Caller.LineNumber actual
-                File.WriteAllLines (state.Caller.FilePath, lines)
+                File.writeAllLines lines state.Caller.FilePath
                 failwith ("Snapshot successfully updated. Previous contents:\n" + oldContents)
 
         match CompletedSnapshotGeneric.passesAssertion state with
         | None ->
-            match mode, GlobalBuilderConfig.bulkUpdate.Value with
+            match mode, GlobalBuilderConfig.isBulkUpdateMode () with
             | Mode.Update, _
-            | _, 1 ->
+            | _, true ->
                 failwith
                     "Snapshot assertion passed, but we are in snapshot-updating mode. Use the `expect` builder instead of `expect'` to assert the contents of a single snapshot; disable `GlobalBuilderConfig.bulkUpdate` to move back to assertion-checking mode."
             | _ -> ()

WoofWare.Expect/Config.fs

@@ -1,12 +1,19 @@
 namespace WoofWare.Expect
 
-open System.Threading
-
 /// Module holding global mutable state controlling the behaviour of WoofWare.Expect
 /// when running in bulk-update mode.
 [<RequireQualifiedAccess>]
 module GlobalBuilderConfig =
-    let internal bulkUpdate = ref 0
+    /// All access to the global mutable state locks on this.
+    let private locker = obj ()
+
+    // Global mutable state ensuring there is at most one `enterBulkUpdateMode`/`updateAllSnapshots` pair running at once.
+    let private bulkUpdate = ref 0
+
+    let private allTests : ResizeArray<CompletedSnapshot> = ResizeArray ()
+
+    let internal isBulkUpdateMode () : bool =
+        lock locker (fun () -> bulkUpdate.Value > 0)
 
     /// <summary>
     /// Call this to make the <c>expect</c> builder register all tests for bulk update as it runs.
@@ -16,11 +23,15 @@ module GlobalBuilderConfig =
     /// The implied global mutable state is liable to interfere with other expect builders in other fixtures otherwise.
     /// </remarks>
     let enterBulkUpdateMode () =
-        if Interlocked.Increment bulkUpdate <> 1 then
-            failwith
-                "WoofWare.Expect requires bulk updates to happen serially: for example, make the test fixture `[<NonParallelizable>]` if you're using NUnit."
+        lock
+            locker
+            (fun () ->
+                if bulkUpdate.Value <> 0 then
+                    failwith
+                        "WoofWare.Expect requires bulk updates to happen serially: for example, make the test fixture `[<NonParallelizable>]` if you're using NUnit."
 
-    let private allTests : ResizeArray<CompletedSnapshot> = ResizeArray ()
+                bulkUpdate.Value <- bulkUpdate.Value + 1
+            )
 
     /// <summary>
     /// Clear the set of failing tests registered by any previous bulk-update runs.
@@ -30,23 +41,30 @@ module GlobalBuilderConfig =
     /// You probably don't need to do this, because your test runner is probably tearing down
     /// anyway after the tests have failed; this is mainly here for WoofWare.Expect's own internal testing.
     /// </remarks>
-    let clearTests () = lock allTests allTests.Clear
+    let clearTests () = lock locker allTests.Clear
 
-    let internal registerTest (s : CompletedSnapshotGeneric<'T>) : unit =
-        let toAdd = s |> CompletedSnapshot.make
-        lock allTests (fun () -> allTests.Add toAdd)
+    let internal registerTest (toAdd : CompletedSnapshot) : unit =
+        lock locker (fun () -> allTests.Add toAdd)
 
     /// <summary>
     /// For all tests whose failures have already been registered,
     /// transform the files on disk so that the failing snapshots now pass.
     /// </summary>
     let updateAllSnapshots () =
-        let bulkUpdate' = Interlocked.Decrement bulkUpdate
+        // It's OK for this to be called when `enterBulkUpdateMode` has not been called, i.e. when `bulkUpdate` has
+        // value 0. That just means we aren't in bulk-update mode, so we expect the following simply to do nothing.
+        // (This is an expected workflow: we expect users to run `updateAllSnapshots` unconditionally in a
+        // one-time tear-down of the test suite, and they use the one-time setup to control whether any work is actually
+        // performed here.)
+        lock
+            locker
+            (fun () ->
+                let allTests = Seq.toArray allTests
 
-        try
-            if bulkUpdate' = 0 then
-                let allTests = lock allTests (fun () -> Seq.toArray allTests)
-                SnapshotUpdate.updateAll allTests
-
-        finally
-            clearTests ()
+                try
+                    SnapshotUpdate.updateAll allTests
+                finally
+                    // double acquiring of reentrant lock is OK, we're not switching threads
+                    clearTests ()
+                    bulkUpdate.Value <- 0
+            )

WoofWare.Expect/Diff.fs

@@ -0,0 +1,309 @@
+namespace WoofWare.Expect
+
+open System.Collections.Generic
+
+/// A unit of measure tagging "positions in a sequence".
+[<Measure>]
+type pos
+
+/// Position in a sequence
+type Position = int<pos>
+
+/// A Patience diff is composed of a sequence of transformations to get from one string to another.
+/// This represents those transformations.
+type DiffOperation<'line> =
+    /// This line is the same on both sides of the diff.
+    /// On the left, it appears at position posA. On the right, at position posB.
+    | Match of posA : Position * posB : Position * line : 'line
+    /// Delete this line, which is at this position.
+    | Delete of posA : Position * line : 'line
+    /// Insert this line at the given position.
+    | Insert of posB : Position * line : 'line
+
+/// The diff between two line-oriented streams. Normally the generic parameter will be `string`, indicating
+/// that the thing being diffed was text.
+type Diff'<'line> = private | Diff of DiffOperation<'line> list
+
+/// The diff between two line-oriented pieces of text.
+type Diff = Diff'<string>
+
+/// A match between positions in two sequences
+type internal LineMatch<'line> =
+    {
+        PosA : Position
+        PosB : Position
+        Line : 'line
+    }
+
+/// Result of finding unique lines in a sequence
+type internal UniqueLines<'line when 'line : comparison> =
+    {
+        /// Map from line content to its position (only for unique lines)
+        LinePositions : Map<'line, Position>
+        /// All line counts (for verification)
+        LineCounts : Map<'line, int>
+    }
+
+/// The diff between two line-oriented pieces of text.
+[<RequireQualifiedAccess>]
+module Diff =
+    /// Find lines that appear exactly once in a sequence
+    let private findUniqueLines (lines : 'line array) : UniqueLines<'line> =
+        let positions = Dictionary<'line, Position> ()
+        let counts = Dictionary<'line, int> ()
+
+        lines
+        |> Array.iteri (fun i line ->
+            if counts.ContainsKey line then
+                counts.[line] <- counts.[line] + 1
+            else
+                counts.[line] <- 1
+                positions.[line] <- i * 1<pos>
+        )
+
+        let uniquePositions =
+            positions
+            |> Seq.filter (fun kvp -> counts.[kvp.Key] = 1)
+            |> Seq.map (fun kvp -> (kvp.Key, kvp.Value))
+            |> Map.ofSeq
+
+        let allCounts = counts |> Seq.map (fun kvp -> (kvp.Key, kvp.Value)) |> Map.ofSeq
+
+        {
+            LinePositions = uniquePositions
+            LineCounts = allCounts
+        }
+
+    /// Find longest increasing subsequence based on B positions
+    let private longestIncreasingSubsequence (matches : LineMatch<'line> array) : LineMatch<'line> list =
+        let n = matches.Length
+
+        if n = 0 then
+            []
+        else
+            // Dynamic programming arrays
+            let lengths = Array.create n 1
+            let parents = Array.create n -1
+
+            // Build LIS
+            for i in 1 .. n - 1 do
+                for j in 0 .. i - 1 do
+                    let bj = matches.[j].PosB
+                    let bi = matches.[i].PosB
+
+                    if bj < bi && lengths.[j] + 1 > lengths.[i] then
+                        lengths.[i] <- lengths.[j] + 1
+                        parents.[i] <- j
+
+            // Find longest sequence
+            let maxLength = Array.max lengths
+            let endIndex = Array.findIndex ((=) maxLength) lengths
+
+            // Reconstruct sequence
+            let rec reconstruct idx acc =
+                if idx = -1 then
+                    acc
+                else
+                    reconstruct parents.[idx] (matches.[idx] :: acc)
+
+            reconstruct endIndex []
+
+    let private myers' (a : 'line array) (b : 'line array) : DiffOperation<'line> list =
+        let rec diffHelper (i : int) (j : int) (acc : DiffOperation<'line> list) =
+            match i < a.Length, j < b.Length with
+            | false, false -> List.rev acc
+            | true, false ->
+                let deletes =
+                    [ i .. a.Length - 1 ] |> List.map (fun idx -> Delete (idx * 1<pos>, a.[idx]))
+
+                (List.rev acc) @ deletes
+            | false, true ->
+                let inserts =
+                    [ j .. b.Length - 1 ] |> List.map (fun idx -> Insert (idx * 1<pos>, b.[idx]))
+
+                (List.rev acc) @ inserts
+            | true, true ->
+                if a.[i] = b.[j] then
+                    diffHelper (i + 1) (j + 1) (Match (i * 1<pos>, j * 1<pos>, a.[i]) :: acc)
+                else
+                    // Look ahead for matches (simple heuristic)
+                    let lookAhead = 3
+
+                    let aheadMatch =
+                        [ 1 .. min lookAhead (min (a.Length - i) (b.Length - j)) ]
+                        |> List.tryFind (fun k -> a.[i + k - 1] = b.[j + k - 1])
+
+                    match aheadMatch with
+                    | Some k when k <= 2 ->
+                        // Delete/insert to get to the match
+                        let ops =
+                            [ 0 .. k - 2 ]
+                            |> List.collect (fun offset ->
+                                [
+                                    Delete ((i + offset) * 1<pos>, a.[i + offset])
+                                    Insert ((j + offset) * 1<pos>, b.[j + offset])
+                                ]
+                            )
+
+                        diffHelper (i + k - 1) (j + k - 1) (List.rev ops @ acc)
+                    | _ ->
+                        // No close match, just delete and insert
+                        diffHelper (i + 1) j (Delete (i * 1<pos>, a.[i]) :: acc)
+
+        diffHelper 0 0 []
+
+    /// Simple Myers diff implementation. You probably want to use `patience` instead, for more human-readable diffs.
+    let myers (a : string array) (b : string array) : Diff = myers' a b |> Diff
+
+    /// Patience diff: a human-readable line-based diff.
+    /// Operates on lines of string; the function `patience` will split on lines for you.
+    let rec patienceLines (a : 'line array) (b : 'line array) : Diff'<'line> =
+        // Handle empty sequences
+        match a.Length, b.Length with
+        | 0, 0 -> [] |> Diff
+        | 0, _ ->
+            b
+            |> Array.mapi (fun i line -> Insert (i * 1<pos>, line))
+            |> Array.toList
+            |> Diff
+        | _, 0 ->
+            a
+            |> Array.mapi (fun i line -> Delete (i * 1<pos>, line))
+            |> Array.toList
+            |> Diff
+        | _, _ ->
+            // Find unique lines
+            let uniqueA = findUniqueLines a
+            let uniqueB = findUniqueLines b
+
+            // Find common unique lines
+            let commonUniques =
+                Set.intersect
+                    (uniqueA.LinePositions |> Map.toSeq |> Seq.map fst |> Set.ofSeq)
+                    (uniqueB.LinePositions |> Map.toSeq |> Seq.map fst |> Set.ofSeq)
+
+            if Set.isEmpty commonUniques then
+                // No unique common lines, fall back to Myers
+                myers' a b |> Diff
+            else
+                // Build matches for unique common lines
+                let matches =
+                    commonUniques
+                    |> Set.toArray
+                    |> Array.map (fun line ->
+                        {
+                            PosA = uniqueA.LinePositions.[line]
+                            PosB = uniqueB.LinePositions.[line]
+                            Line = line
+                        }
+                    )
+                    |> Array.sortBy (fun m -> m.PosA)
+
+                // Find LIS
+                let anchorMatches = longestIncreasingSubsequence matches |> List.toArray
+
+                // Build diff imperatively
+                let result = ResizeArray<DiffOperation<_>> ()
+                let mutable prevA = 0<pos>
+                let mutable prevB = 0<pos>
+
+                // Process each anchor
+                for anchor in anchorMatches do
+                    let anchorA = anchor.PosA
+                    let anchorB = anchor.PosB
+
+                    // Add diff for section before this anchor
+                    if prevA < anchorA || prevB < anchorB then
+                        let sectionA = a.[prevA / 1<pos> .. anchorA / 1<pos> - 1]
+                        let sectionB = b.[prevB / 1<pos> .. anchorB / 1<pos> - 1]
+                        let (Diff sectionDiff) = patienceLines sectionA sectionB
+
+                        // Adjust positions and add to result
+                        for op in sectionDiff do
+                            match op with
+                            | Match (pa, pb, line) -> result.Add (Match ((pa + prevA), (pb + prevB), line))
+                            | Delete (pa, line) -> result.Add (Delete ((pa + prevA), line))
+                            | Insert (pb, line) -> result.Add (Insert ((pb + prevB), line))
+
+                    // Add the anchor match
+                    result.Add (Match (anchor.PosA, anchor.PosB, anchor.Line))
+
+                    // Update positions
+                    prevA <- anchorA + 1<pos>
+                    prevB <- anchorB + 1<pos>
+
+                // Handle remaining elements after last anchor
+                if prevA / 1<pos> < a.Length || prevB / 1<pos> < b.Length then
+                    let remainingA = a.[prevA / 1<pos> ..]
+                    let remainingB = b.[prevB / 1<pos> ..]
+                    let (Diff remainingDiff) = patienceLines remainingA remainingB
+
+                    for op in remainingDiff do
+                        match op with
+                        | Match (pa, pb, line) -> result.Add (Match ((pa + prevA), (pb + prevB), line))
+                        | Delete (pa, line) -> result.Add (Delete ((pa + prevA), line))
+                        | Insert (pb, line) -> result.Add (Insert ((pb + prevB), line))
+
+                result |> Seq.toList |> Diff
+
+    /// Patience diff: a human-readable line-based diff.
+    let patience (a : string) (b : string) =
+        patienceLines (a.Split '\n') (b.Split '\n')
+
+    /// Format the diff as a human-readable string, including line numbers at the left.
+    let formatWithLineNumbers' (formatter : 'line -> string) (Diff ops) : string =
+        ops
+        |> List.map (fun op ->
+            match op with
+            | Match (a, b, line) -> sprintf "  %3d %3d  %s" a b (formatter line)
+            | Delete (a, line) -> sprintf "- %3d      %s" a (formatter line)
+            | Insert (b, line) -> sprintf "+     %3d  %s" b (formatter line)
+        )
+        |> String.concat "\n"
+
+    /// Format the diff as a human-readable string, including line numbers at the left.
+    let formatWithLineNumbers (d : Diff) : string = formatWithLineNumbers' id d
+
+    /// Format the diff as a human-readable string.
+    let format' (formatter : 'line -> string) (Diff ops) : string =
+        ops
+        |> List.map (fun op ->
+            match op with
+            | Match (_, _, line) -> "  " + (formatter line)
+            | Delete (_, line) -> "- " + (formatter line)
+            | Insert (_, line) -> "+ " + (formatter line)
+        )
+        |> String.concat "\n"
+
+    /// Format the diff as a human-readable string.
+    let format (ops : Diff) : string = format' id ops
+
+    /// Compute diff statistics
+    type internal DiffStats =
+        {
+            Matches : int
+            Deletions : int
+            Insertions : int
+            TotalOperations : int
+        }
+
+    let internal computeStats (ops : DiffOperation<'a> list) : DiffStats =
+        let counts =
+            ops
+            |> List.fold
+                (fun (m, d, i) op ->
+                    match op with
+                    | Match _ -> (m + 1, d, i)
+                    | Delete _ -> (m, d + 1, i)
+                    | Insert _ -> (m, d, i + 1)
+                )
+                (0, 0, 0)
+
+        let matches, deletions, insertions = counts
+
+        {
+            Matches = matches
+            Deletions = deletions
+            Insertions = insertions
+            TotalOperations = matches + deletions + insertions
+        }

WoofWare.Expect/Domain.fs

@@ -1,5 +1,6 @@
 namespace WoofWare.Expect
 
+open System.Collections
 open System.Text.Json
 open System.Text.Json.Serialization
 
@@ -17,20 +18,30 @@ type CallerInfo =
 type private SnapshotValue =
     | Json of expected : string
     | Formatted of expected : string
+    | ThrowsException of expected : string
 
 type private CompletedSnapshotValue<'T> =
     | Json of expected : string * JsonSerializerOptions * JsonDocumentOptions
-    | Formatted of expected : string * format : ('T -> string)
+    | Formatted of expected : string * format : ((unit -> 'T) -> string)
 
 /// The state accumulated by the `expect` builder. You should never find yourself interacting with this type.
 type ExpectState<'T> =
     private
         {
-            Formatter : ('T -> string) option
+            Formatter : ((unit -> 'T) -> string) option
             JsonSerialiserOptions : JsonSerializerOptions option
             JsonDocOptions : JsonDocumentOptions option
             Snapshot : (SnapshotValue * CallerInfo) option
-            Actual : 'T option
+            Actual : (unit -> 'T) option
+        }
+
+/// The state accumulated by the `expect` builder. You should never find yourself interacting with this type.
+type ExpectStateListy<'T> =
+    private
+        {
+            Formatter : ((unit -> 'T) -> string) option
+            Snapshot : (string list * CallerInfo) option
+            Actual : (unit -> 'T seq) option
         }
 
 /// The state accumulated by the `expect` builder. You should never find yourself interacting with this type.
@@ -39,7 +50,7 @@ type internal CompletedSnapshotGeneric<'T> =
         {
             SnapshotValue : CompletedSnapshotValue<'T>
             Caller : CallerInfo
-            Actual : 'T
+            Actual : unit -> 'T
         }
 
 [<RequireQualifiedAccess>]
@@ -68,11 +79,22 @@ module internal CompletedSnapshotGeneric =
                 | SnapshotValue.Formatted expected ->
                     let formatter =
                         match state.Formatter with
-                        | None -> fun x -> x.ToString ()
+                        | None -> fun x -> x().ToString ()
                         | Some f -> f
 
                     CompletedSnapshotValue.Formatted (expected, formatter)
 
+                | SnapshotValue.ThrowsException expected ->
+                    CompletedSnapshotValue.Formatted (
+                        expected,
+                        fun x ->
+                            try
+                                x () |> ignore
+                                "<no exception raised>"
+                            with e ->
+                                e.GetType().FullName + ": " + e.Message
+                    )
+
             {
                 SnapshotValue = snapshot
                 Caller = source
@@ -84,7 +106,7 @@ module internal CompletedSnapshotGeneric =
     let internal replacement (s : CompletedSnapshotGeneric<'T>) =
         match s.SnapshotValue with
         | CompletedSnapshotValue.Json (_existing, options, _) ->
-            JsonSerializer.Serialize (s.Actual, options)
+            JsonSerializer.Serialize (s.Actual (), options)
             |> JsonDocument.Parse
             |> _.RootElement
             |> _.ToString()
@@ -104,7 +126,7 @@ module internal CompletedSnapshotGeneric =
                     None
 
             let canonicalActual =
-                JsonSerializer.Serialize (state.Actual, jsonSerOptions) |> JsonDocument.Parse
+                JsonSerializer.Serialize (state.Actual (), jsonSerOptions) |> JsonDocument.Parse
 
             match canonicalSnapshot with
             | None -> Some ("[JSON failed to parse:] " + snapshot, canonicalActual.RootElement.ToString ())
@@ -114,18 +136,69 @@ module internal CompletedSnapshotGeneric =
                 else
                     None
 
-/// Represents a snapshot test that has failed and is awaiting update or report to the user.
-type CompletedSnapshot =
-    internal
+type internal CompletedListSnapshotGeneric<'elt> =
+    private
         {
-            CallerInfo : CallerInfo
-            Replacement : string
+            Expected : string list
+            Format : 'elt -> string
+            Caller : CallerInfo
+            Actual : unit -> 'elt seq
         }
 
 [<RequireQualifiedAccess>]
-module internal CompletedSnapshot =
-    let make (s : CompletedSnapshotGeneric<'T>) =
+module internal CompletedListSnapshotGeneric =
+    let replacement (s : CompletedListSnapshotGeneric<'T>) =
+        s.Actual () |> unbox<IEnumerable> |> Seq.cast |> Seq.map s.Format |> Seq.toList
+
+    /// Returns None if the assertion passes, or Some (expected, actual) if the assertion fails.
+    let internal passesAssertion (state : CompletedListSnapshotGeneric<'T>) : (string list * string list) option =
+        let actual =
+            state.Actual ()
+            |> unbox<IEnumerable>
+            |> Seq.cast
+            |> Seq.map state.Format
+            |> Seq.toList
+
+        if state.Expected <> actual then
+            Some (state.Expected, actual)
+        else
+            None
+
+    let make (state : ExpectStateListy<'elt>) : CompletedListSnapshotGeneric<'elt> =
+        match state.Actual with
+        | None -> failwith "expected an assertion, but got none"
+        | Some actual ->
+
+        match state.Snapshot with
+        | None -> failwith "expected a snapshotList, but got none"
+        | Some (snapshot, caller) ->
+
+        let formatter =
+            match state.Formatter with
+            | Some f -> fun x -> f (fun () -> x)
+            | None -> fun x -> x.ToString ()
+
         {
-            CallerInfo = s.Caller
-            Replacement = CompletedSnapshotGeneric.replacement s
+            Expected = snapshot
+            Format = formatter
+            Caller = caller
+            Actual = actual
         }
+
+/// Represents a snapshot test that has failed and is awaiting update or report to the user.
+type internal CompletedSnapshot =
+    | GuessString of CallerInfo * replacement : string
+    | Known of CallerInfo * replacement : string list * SnapshotLocation
+
+    member this.CallerInfo =
+        match this with
+        | CompletedSnapshot.GuessString (c, _) -> c
+        | CompletedSnapshot.Known (c, _, _) -> c
+
+[<RequireQualifiedAccess>]
+module internal CompletedSnapshot =
+    let makeGuess (s : CompletedSnapshotGeneric<'T>) =
+        CompletedSnapshot.GuessString (s.Caller, CompletedSnapshotGeneric.replacement s)
+
+    let makeFromAst (source : SnapshotLocation) (s : CompletedListSnapshotGeneric<'elt>) =
+        CompletedSnapshot.Known (s.Caller, CompletedListSnapshotGeneric.replacement s, source)

WoofWare.Expect/Dot.fs

@@ -0,0 +1,91 @@
+namespace WoofWare.Expect
+
+open System
+open System.Diagnostics
+open System.IO
+
+/// Methods for rendering dot files (specifications of graphs).
+[<RequireQualifiedAccess>]
+module Dot =
+    /// A mock for System.Diagnostics.Process.
+    type IProcess<'Process when 'Process :> IDisposable> =
+        /// Equivalent to Process.Create
+        abstract Create : exe : string -> args : string -> 'Process
+        /// Equivalent to Process.Start
+        abstract Start : 'Process -> bool
+        /// Equivalent to Process.WaitForExit
+        abstract WaitForExit : 'Process -> unit
+        /// Equivalent to Process.StandardOutput.ReadToEnd
+        abstract ReadStandardOutput : 'Process -> string
+        /// Equivalent to Process.ExitCode
+        abstract ExitCode : 'Process -> int
+
+    /// The real Process interface, in a form that can be passed to `render'`.
+    let process' =
+        { new IProcess<Process> with
+            member _.Create exe args =
+                let psi = ProcessStartInfo exe
+                psi.RedirectStandardOutput <- true
+                psi.Arguments <- args
+                let result = new Process ()
+                result.StartInfo <- psi
+                result
+
+            member _.Start p = p.Start ()
+            member _.WaitForExit p = p.WaitForExit ()
+            member _.ReadStandardOutput p = p.StandardOutput.ReadToEnd ()
+            member _.ExitCode p = p.ExitCode
+        }
+
+    /// A mock for System.IO
+    type IFileSystem =
+        /// Equivalent to Path.GetTempFileName
+        abstract GetTempFileName : unit -> string
+        /// Equivalent to File.Delete
+        abstract DeleteFile : string -> unit
+        /// Equivalent to File.WriteAllText (curried)
+        abstract WriteFile : path : string -> contents : string -> unit
+
+    /// The real filesystem, in a form that can be passed to `render'`.
+    let fileSystem =
+        { new IFileSystem with
+            member _.GetTempFileName () = Path.GetTempFileName ()
+            member _.DeleteFile f = File.Delete f
+            member _.WriteFile path contents = File.WriteAllText (path, contents)
+        }
+
+    /// writeFile takes the filepath first and the contents second.
+    /// Due to the impoverished nature of the .NET Standard APIs, you are in charge of making sure the output of
+    /// fs.GetTempFileName is suitable for interpolation into a command line.
+    let render'<'Process when 'Process :> IDisposable>
+        (pr : IProcess<'Process>)
+        (fs : IFileSystem)
+        (graphEasyExecutable : string)
+        (dotFileContents : string)
+        : string
+        =
+        let tempFile = fs.GetTempFileName ()
+
+        try
+            fs.WriteFile tempFile dotFileContents
+
+            use p = pr.Create graphEasyExecutable ("--as=boxart --from=dot " + tempFile)
+            pr.Start p |> ignore<bool>
+            pr.WaitForExit p
+
+            let stdout = pr.ReadStandardOutput p
+            let exitCode = pr.ExitCode p
+
+            if exitCode <> 0 then
+                failwithf "failed to run; exit code: %i. stdout:\n%s" exitCode stdout
+
+            "\n" + stdout
+        finally
+            try
+                fs.DeleteFile tempFile
+            with _ ->
+                ()
+
+    /// Call `graph-easy` to render the dotfile as ASCII art.
+    /// This is fully mockable, but you must use `render'` to do so.
+    let render = render' process' fileSystem "graph-easy"

WoofWare.Expect/File.fs

@@ -0,0 +1,32 @@
+namespace WoofWare.Expect
+
+open System
+open System.IO
+
+[<RequireQualifiedAccess>]
+module internal File =
+
+    /// Standard attempt at an atomic file write.
+    /// It may fail to be atomic if the working directory somehow spans multiple volumes,
+    /// and of course with external network storage all bets are off.
+    let writeAllLines (lines : string[]) (path : string) : unit =
+        let file = FileInfo path
+
+        let tempFile =
+            Path.Combine (file.Directory.FullName, file.Name + "." + Guid.NewGuid().ToString () + ".tmp")
+
+        try
+            File.WriteAllLines (tempFile, lines)
+            // Atomicity guarantees are undocumented, but on Unix this is an atomic `rename` call
+            // https://github.com/dotnet/runtime/blob/9a4be5b56d81aa04c7ea687c02b3f4e64c83761b/src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Unix.cs#L181
+            // and on Windows this is an atomic ReplaceFile:
+            // https://github.com/dotnet/runtime/blob/9a4be5b56d81aa04c7ea687c02b3f4e64c83761b/src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs#L92
+            // calls https://github.com/dotnet/runtime/blob/9a4be5b56d81aa04c7ea687c02b3f4e64c83761b/src/libraries/Common/src/Interop/Windows/Kernel32/Interop.ReplaceFile.cs#L12
+            // which calls ReplaceFileW, whose atomicity guarantees are again apparently undocumented,
+            // but 4o-turbo, Opus 4, and Gemini 2.5 Flash all think it's atomic.
+            File.Replace (tempFile, path, null)
+        finally
+            try
+                File.Delete tempFile
+            with _ ->
+                ()

WoofWare.Expect/SnapshotUpdate.fs

@@ -15,7 +15,7 @@ type private StringLiteralInfo =
     override this.ToString () =
         sprintf "%i:%i to %i:%i: %s" this.StartLine this.StartColumn this.EndLine this.EndColumn this.Content
 
-type private Position =
+type private SnapshotPosition =
     {
         Line : int
         Column : int
@@ -28,8 +28,8 @@ module internal SnapshotUpdate =
     let tripleQuote = "\"\"\""
 
     /// Convert a string position to line/column
-    let private positionToLineColumn (text : string) (offset : int) : Position =
-        let rec loop (line : int) (col : int) (totalOffset : int) (i : int) : Position =
+    let private positionToLineColumn (text : string) (offset : int) : SnapshotPosition =
+        let rec loop (line : int) (col : int) (totalOffset : int) (i : int) : SnapshotPosition =
             if i >= text.Length || totalOffset = offset then
                 {
                     Line = line
@@ -147,7 +147,8 @@ module internal SnapshotUpdate =
             let searchText = String.concat "\n" relevantLines
 
             // Find snapshot keyword
-            let snapshotMatch = Regex.Match (searchText, @"\b(snapshot|snapshotJson)\b")
+            let snapshotMatch =
+                Regex.Match (searchText, @"\b(snapshot|snapshotJson|snapshotThrows)\b")
 
             if not snapshotMatch.Success then
                 None
@@ -202,11 +203,22 @@ module internal SnapshotUpdate =
                         )
                 )
 
+    let internal stringLiteral (content : string) =
+        if
+            (content.IndexOf '\n' < 0)
+            && (content.IndexOf '\\' < 0)
+            && (content.IndexOf '"' < 0)
+        then
+            // simple case where there's no escaping
+            "\"" + content + "\""
+        else
+            "@\"" + content.Replace ("\"", "\"\"") + "\""
+
     /// Update the snapshot string with a new value; this doesn't edit the file on disk, but
     /// instead returns the new contents.
     /// We always write single-quoted @-strings for simplicity.
     let private updateSnapshot (lines : string[]) (info : StringLiteralInfo) (newContent : string) : string[] =
-        let newString = "@\"" + newContent.Replace ("\"", "\"\"") + "\""
+        let newString = stringLiteral newContent
 
         if info.StartLine = info.EndLine then
             // Single line update
@@ -229,7 +241,7 @@ module internal SnapshotUpdate =
 
             let newLines =
                 if newContent.IndexOf '\n' >= 0 then
-                    let split = newContent.Replace("\"", "\"\"").Split ('\n')
+                    let split = newContent.Replace("\"", "\"\"").Split '\n'
 
                     match split with
                     | [||] -> failwith "expected contents from split string"
@@ -286,6 +298,27 @@ module internal SnapshotUpdate =
         |> Seq.sortByDescending fst
         |> Seq.fold (fun lines (lineNum, replacement) -> updateSnapshotAtLine lines lineNum replacement) fileLines
 
+    let internal updateAtLocation (source : SnapshotLocation) (lines : string[]) (actual : string seq) =
+        let indent = String.replicate source.KeywordRange.StartColumn " "
+
+        [|
+            // Range's lines are one-indexed!
+            lines.[0 .. source.KeywordRange.EndLine - 2]
+            [|
+                lines.[source.KeywordRange.EndLine - 1].Substring (0, source.KeywordRange.EndColumn)
+                + " ["
+            |]
+            actual |> Seq.map (fun s -> indent + "    " + stringLiteral s) |> Array.ofSeq
+            [|
+                indent
+                + "]"
+                + lines.[source.ReplacementRange.EndLine - 1].Substring source.ReplacementRange.EndColumn
+            |]
+            lines.[source.ReplacementRange.EndLine ..]
+        |]
+        |> Array.concat
+
+
     /// <summary>
     /// Update every failed snapshot in the input, editing the files on disk.
     /// </summary>
@@ -295,10 +328,19 @@ module internal SnapshotUpdate =
         |> Seq.iter (fun (callerFile, callers) ->
             let contents = System.IO.File.ReadAllLines callerFile
 
-            let sources =
-                callers |> Seq.map (fun csc -> csc.CallerInfo.LineNumber, csc.Replacement)
+            let newContents =
+                callers
+                |> Seq.map (fun csc -> csc.CallerInfo.LineNumber, csc)
+                |> Seq.sortByDescending fst
+                |> Seq.fold
+                    (fun lines (lineNum, replacement) ->
+                        match replacement with
+                        | CompletedSnapshot.GuessString (_, replacement) ->
+                            updateSnapshotAtLine lines lineNum replacement
+                        | CompletedSnapshot.Known (_, replacement, snapshotLocation) ->
+                            updateAtLocation snapshotLocation lines replacement
+                    )
+                    contents
 
-            let newContents = updateAllLines contents sources
-
-            System.IO.File.WriteAllLines (callerFile, newContents)
+            File.writeAllLines newContents callerFile
         )

WoofWare.Expect/SurfaceBaseline.txt

@@ -6,22 +6,94 @@ WoofWare.Expect.Builder.get_expect [static method]: unit -> WoofWare.Expect.Expe
 WoofWare.Expect.Builder.get_expect' [static method]: unit -> WoofWare.Expect.ExpectBuilder
 WoofWare.Expect.CallerInfo inherit obj, implements WoofWare.Expect.CallerInfo System.IEquatable, System.Collections.IStructuralEquatable, WoofWare.Expect.CallerInfo System.IComparable, System.IComparable, System.Collections.IStructuralComparable
 WoofWare.Expect.CallerInfo.Equals [method]: (WoofWare.Expect.CallerInfo, System.Collections.IEqualityComparer) -> bool
-WoofWare.Expect.CompletedSnapshot inherit obj, implements WoofWare.Expect.CompletedSnapshot System.IEquatable, System.Collections.IStructuralEquatable, WoofWare.Expect.CompletedSnapshot System.IComparable, System.IComparable, System.Collections.IStructuralComparable
-WoofWare.Expect.CompletedSnapshot.Equals [method]: (WoofWare.Expect.CompletedSnapshot, System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.Diff'`1 inherit obj, implements 'line WoofWare.Expect.Diff' System.IEquatable, System.Collections.IStructuralEquatable, 'line WoofWare.Expect.Diff' System.IComparable, System.IComparable, System.Collections.IStructuralComparable
+WoofWare.Expect.Diff'`1.Equals [method]: ('line WoofWare.Expect.Diff', System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.DiffModule inherit obj
+WoofWare.Expect.DiffModule.format [static method]: string WoofWare.Expect.Diff' -> string
+WoofWare.Expect.DiffModule.format' [static method]: ('line -> string) -> 'line WoofWare.Expect.Diff' -> string
+WoofWare.Expect.DiffModule.formatWithLineNumbers [static method]: string WoofWare.Expect.Diff' -> string
+WoofWare.Expect.DiffModule.formatWithLineNumbers' [static method]: ('line -> string) -> 'line WoofWare.Expect.Diff' -> string
+WoofWare.Expect.DiffModule.myers [static method]: string [] -> string [] -> string WoofWare.Expect.Diff'
+WoofWare.Expect.DiffModule.patience [static method]: string -> string -> string WoofWare.Expect.Diff'
+WoofWare.Expect.DiffModule.patienceLines [static method]: 'line [] -> 'line [] -> 'line WoofWare.Expect.Diff'
+WoofWare.Expect.DiffOperation`1 inherit obj, implements 'line WoofWare.Expect.DiffOperation System.IEquatable, System.Collections.IStructuralEquatable, 'line WoofWare.Expect.DiffOperation System.IComparable, System.IComparable, System.Collections.IStructuralComparable - union type with 3 cases
+WoofWare.Expect.DiffOperation`1+Delete inherit 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1+Delete.get_line [method]: unit -> 'line
+WoofWare.Expect.DiffOperation`1+Delete.get_posA [method]: unit -> int
+WoofWare.Expect.DiffOperation`1+Delete.line [property]: [read-only] 'line
+WoofWare.Expect.DiffOperation`1+Delete.posA [property]: [read-only] int
+WoofWare.Expect.DiffOperation`1+Insert inherit 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1+Insert.get_line [method]: unit -> 'line
+WoofWare.Expect.DiffOperation`1+Insert.get_posB [method]: unit -> int
+WoofWare.Expect.DiffOperation`1+Insert.line [property]: [read-only] 'line
+WoofWare.Expect.DiffOperation`1+Insert.posB [property]: [read-only] int
+WoofWare.Expect.DiffOperation`1+Match inherit 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1+Match.get_line [method]: unit -> 'line
+WoofWare.Expect.DiffOperation`1+Match.get_posA [method]: unit -> int
+WoofWare.Expect.DiffOperation`1+Match.get_posB [method]: unit -> int
+WoofWare.Expect.DiffOperation`1+Match.line [property]: [read-only] 'line
+WoofWare.Expect.DiffOperation`1+Match.posA [property]: [read-only] int
+WoofWare.Expect.DiffOperation`1+Match.posB [property]: [read-only] int
+WoofWare.Expect.DiffOperation`1+Tags inherit obj
+WoofWare.Expect.DiffOperation`1+Tags.Delete [static field]: int = 1
+WoofWare.Expect.DiffOperation`1+Tags.Insert [static field]: int = 2
+WoofWare.Expect.DiffOperation`1+Tags.Match [static field]: int = 0
+WoofWare.Expect.DiffOperation`1.Equals [method]: ('line WoofWare.Expect.DiffOperation, System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.DiffOperation`1.get_IsDelete [method]: unit -> bool
+WoofWare.Expect.DiffOperation`1.get_IsInsert [method]: unit -> bool
+WoofWare.Expect.DiffOperation`1.get_IsMatch [method]: unit -> bool
+WoofWare.Expect.DiffOperation`1.get_Tag [method]: unit -> int
+WoofWare.Expect.DiffOperation`1.IsDelete [property]: [read-only] bool
+WoofWare.Expect.DiffOperation`1.IsInsert [property]: [read-only] bool
+WoofWare.Expect.DiffOperation`1.IsMatch [property]: [read-only] bool
+WoofWare.Expect.DiffOperation`1.NewDelete [static method]: (int, 'line) -> 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1.NewInsert [static method]: (int, 'line) -> 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1.NewMatch [static method]: (int, int, 'line) -> 'line WoofWare.Expect.DiffOperation
+WoofWare.Expect.DiffOperation`1.Tag [property]: [read-only] int
+WoofWare.Expect.Dot inherit obj
+WoofWare.Expect.Dot+IFileSystem - interface with 3 member(s)
+WoofWare.Expect.Dot+IFileSystem.DeleteFile [method]: string -> unit
+WoofWare.Expect.Dot+IFileSystem.GetTempFileName [method]: unit -> string
+WoofWare.Expect.Dot+IFileSystem.WriteFile [method]: string -> string -> unit
+WoofWare.Expect.Dot+IProcess`1 - interface with 5 member(s)
+WoofWare.Expect.Dot+IProcess`1.Create [method]: string -> string -> #(IDisposable)
+WoofWare.Expect.Dot+IProcess`1.ExitCode [method]: #(IDisposable) -> int
+WoofWare.Expect.Dot+IProcess`1.ReadStandardOutput [method]: #(IDisposable) -> string
+WoofWare.Expect.Dot+IProcess`1.Start [method]: #(IDisposable) -> bool
+WoofWare.Expect.Dot+IProcess`1.WaitForExit [method]: #(IDisposable) -> unit
+WoofWare.Expect.Dot.fileSystem [static property]: [read-only] WoofWare.Expect.Dot+IFileSystem
+WoofWare.Expect.Dot.get_fileSystem [static method]: unit -> WoofWare.Expect.Dot+IFileSystem
+WoofWare.Expect.Dot.get_process' [static method]: unit -> System.Diagnostics.Process WoofWare.Expect.Dot+IProcess
+WoofWare.Expect.Dot.get_render [static method]: unit -> (string -> string)
+WoofWare.Expect.Dot.process' [static property]: [read-only] System.Diagnostics.Process WoofWare.Expect.Dot+IProcess
+WoofWare.Expect.Dot.render [static property]: [read-only] string -> string
+WoofWare.Expect.Dot.render' [static method]: #(IDisposable) WoofWare.Expect.Dot+IProcess -> WoofWare.Expect.Dot+IFileSystem -> string -> string -> string
 WoofWare.Expect.ExpectBuilder inherit obj
 WoofWare.Expect.ExpectBuilder..ctor [constructor]: (string * int)
 WoofWare.Expect.ExpectBuilder..ctor [constructor]: bool
 WoofWare.Expect.ExpectBuilder..ctor [constructor]: WoofWare.Expect.Mode
+WoofWare.Expect.ExpectBuilder.Bind [method]: ('elt WoofWare.Expect.ExpectStateListy, unit -> #('elt seq) WoofWare.Expect.ExpectState) -> 'elt WoofWare.Expect.ExpectStateListy
 WoofWare.Expect.ExpectBuilder.Bind [method]: ('U WoofWare.Expect.ExpectState, unit -> 'U WoofWare.Expect.ExpectState) -> 'U WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.Bind [method]: ('U WoofWare.Expect.ExpectStateListy, unit -> 'U WoofWare.Expect.ExpectStateListy) -> 'U WoofWare.Expect.ExpectStateListy
 WoofWare.Expect.ExpectBuilder.Delay [method]: (unit -> 'T WoofWare.Expect.ExpectState) -> (unit -> 'T WoofWare.Expect.ExpectState)
+WoofWare.Expect.ExpectBuilder.Delay [method]: (unit -> 'T WoofWare.Expect.ExpectStateListy) -> (unit -> 'T WoofWare.Expect.ExpectStateListy)
 WoofWare.Expect.ExpectBuilder.Return [method]: 'T -> 'T WoofWare.Expect.ExpectState
-WoofWare.Expect.ExpectBuilder.Return [method]: unit -> 'T WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.Return [method]: unit -> 'T WoofWare.Expect.ExpectStateListy
+WoofWare.Expect.ExpectBuilder.ReturnFrom [method]: (unit -> 'T) -> 'T WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectBuilder.Run [method]: (unit -> 'T WoofWare.Expect.ExpectState) -> unit
+WoofWare.Expect.ExpectBuilder.Run [method]: (unit -> 'T WoofWare.Expect.ExpectStateListy) -> unit
 WoofWare.Expect.ExpectBuilder.Snapshot [method]: ('a WoofWare.Expect.ExpectState, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.Snapshot [method]: ('a WoofWare.Expect.ExpectStateListy, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectBuilder.SnapshotJson [method]: (unit WoofWare.Expect.ExpectState, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.SnapshotJson [method]: (unit WoofWare.Expect.ExpectStateListy, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.SnapshotList [method]: (unit WoofWare.Expect.ExpectStateListy, string list, string option, int option, string option) -> 'a WoofWare.Expect.ExpectStateListy
+WoofWare.Expect.ExpectBuilder.SnapshotThrows [method]: ('a WoofWare.Expect.ExpectState, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.SnapshotThrows [method]: ('a WoofWare.Expect.ExpectStateListy, string, string option, int option, string option) -> 'a WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectBuilder.WithFormat [method]: ('T WoofWare.Expect.ExpectState, 'T -> string) -> 'T WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.WithFormat [method]: ('T WoofWare.Expect.ExpectStateListy, 'T -> string) -> 'T WoofWare.Expect.ExpectStateListy
 WoofWare.Expect.ExpectBuilder.WithJsonDocOptions [method]: ('T WoofWare.Expect.ExpectState, System.Text.Json.JsonDocumentOptions) -> 'T WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectBuilder.WithJsonSerializerOptions [method]: ('T WoofWare.Expect.ExpectState, System.Text.Json.JsonSerializerOptions) -> 'T WoofWare.Expect.ExpectState
+WoofWare.Expect.ExpectBuilder.WithJsonSerializerOptions [method]: ('T WoofWare.Expect.ExpectStateListy, System.Text.Json.JsonSerializerOptions) -> 'T WoofWare.Expect.ExpectState
 WoofWare.Expect.ExpectException inherit System.Exception, implements System.Collections.IStructuralEquatable
 WoofWare.Expect.ExpectException..ctor [constructor]: string
 WoofWare.Expect.ExpectException..ctor [constructor]: unit
@@ -29,9 +101,11 @@ WoofWare.Expect.ExpectException.Equals [method]: (System.Exception, System.Colle
 WoofWare.Expect.ExpectException.Equals [method]: System.Exception -> bool
 WoofWare.Expect.ExpectException.Message [property]: [read-only] string
 WoofWare.Expect.ExpectState`1 inherit obj
+WoofWare.Expect.ExpectStateListy`1 inherit obj
 WoofWare.Expect.GlobalBuilderConfig inherit obj
 WoofWare.Expect.GlobalBuilderConfig.clearTests [static method]: unit -> unit
 WoofWare.Expect.GlobalBuilderConfig.enterBulkUpdateMode [static method]: unit -> unit
 WoofWare.Expect.GlobalBuilderConfig.updateAllSnapshots [static method]: unit -> unit
 WoofWare.Expect.Mode inherit obj, implements WoofWare.Expect.Mode System.IEquatable, System.Collections.IStructuralEquatable, WoofWare.Expect.Mode System.IComparable, System.IComparable, System.Collections.IStructuralComparable
-WoofWare.Expect.Mode.Equals [method]: (WoofWare.Expect.Mode, System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.Mode.Equals [method]: (WoofWare.Expect.Mode, System.Collections.IEqualityComparer) -> bool
+WoofWare.Expect.pos inherit obj

WoofWare.Expect/WoofWare.Expect.fsproj

@@ -18,6 +18,10 @@
     <ItemGroup>
         <Compile Include="AssemblyInfo.fs" />
         <Compile Include="Text.fs" />
+        <Compile Include="File.fs" />
+        <Compile Include="Diff.fs" />
+        <Compile Include="Dot.fs" />
+        <Compile Include="AstWalker.fs" />
         <Compile Include="Domain.fs" />
         <Compile Include="SnapshotUpdate.fs" />
         <Compile Include="Config.fs" />
@@ -36,8 +40,9 @@
 
     <ItemGroup>
       <!-- FSharp.SystemTextJson requires at least this version -->
-      <PackageReference Update="FSharp.Core" Version="4.7.0" />
+      <PackageReference Update="FSharp.Core" Version="8.0.100" />
       <PackageReference Include="FSharp.SystemTextJson" Version="1.4.36" />
+      <PackageReference Include="Fantomas.FCS" Version="7.0.3" />
       <!-- Needed for DeepEquals -->
       <PackageReference Include="System.Text.Json" Version="9.0.0" />
     </ItemGroup>

WoofWare.Expect/version.json

@@ -1,5 +1,5 @@
 {
-  "version": "0.4",
+  "version": "0.8",
   "publicReleaseRefSpec": [
     "^refs/heads/main$"
   ],

flake.nix

@@ -65,6 +65,8 @@
           pkgs.alejandra
           pkgs.nodePackages.markdown-link-check
           pkgs.shellcheck
+          pkgs.xmlstarlet
+          pkgs.graph-easy
         ];
       };
     });

nix/deps.json

@@ -9,6 +9,11 @@
     "version": "7.0.2",
     "hash": "sha256-BAaENIm/ksTiXrUImRgKoIXTGIlgsX7ch6ayoFjhJXA="
   },
+  {
+    "pname": "Fantomas.FCS",
+    "version": "7.0.3",
+    "hash": "sha256-BmCUq+ZQ3b25nrMBTc5tcxdO2soryEjNx9Fn/FJpi1c="
+  },
   {
     "pname": "fsharp-analyzers",
     "version": "0.31.0",
@@ -16,8 +21,8 @@
   },
   {
     "pname": "FSharp.Core",
-    "version": "4.7.0",
-    "hash": "sha256-7aa4bga9XWLkq7J5KXv8Bilf1KGum77lSUqp+ooYIUg="
+    "version": "8.0.100",
+    "hash": "sha256-FCjhq+W603ibz9XAA9iH5K6gJhX02/pMHyge6dHb4xs="
   },
   {
     "pname": "FSharp.Core",
@@ -59,11 +64,26 @@
     "version": "1.1.0",
     "hash": "sha256-FeM40ktcObQJk4nMYShB61H/E8B7tIKfl9ObJ0IOcCM="
   },
+  {
+    "pname": "Microsoft.NETCore.Platforms",
+    "version": "1.1.1",
+    "hash": "sha256-8hLiUKvy/YirCWlFwzdejD2Db3DaXhHxT7GSZx/znJg="
+  },
   {
     "pname": "Microsoft.NETCore.Platforms",
     "version": "2.0.0",
     "hash": "sha256-IEvBk6wUXSdyCnkj6tHahOJv290tVVT8tyemYcR0Yro="
   },
+  {
+    "pname": "Microsoft.NETCore.Targets",
+    "version": "1.1.0",
+    "hash": "sha256-0AqQ2gMS8iNlYkrD+BxtIg7cXMnr9xZHtKAuN4bjfaQ="
+  },
+  {
+    "pname": "Microsoft.NETCore.Targets",
+    "version": "1.1.3",
+    "hash": "sha256-WLsf1NuUfRWyr7C7Rl9jiua9jximnVvzy6nk2D2bVRc="
+  },
   {
     "pname": "Microsoft.Testing.Extensions.Telemetry",
     "version": "1.5.3",
@@ -159,11 +179,31 @@
     "version": "5.0.0",
     "hash": "sha256-7jZM4qAbIzne3AcdFfMbvbgogqpxvVe6q2S7Ls8xQy0="
   },
+  {
+    "pname": "runtime.any.System.Runtime",
+    "version": "4.3.0",
+    "hash": "sha256-qwhNXBaJ1DtDkuRacgHwnZmOZ1u9q7N8j0cWOLYOELM="
+  },
+  {
+    "pname": "runtime.native.System",
+    "version": "4.3.0",
+    "hash": "sha256-ZBZaodnjvLXATWpXXakFgcy6P+gjhshFXmglrL5xD5Y="
+  },
+  {
+    "pname": "runtime.unix.System.Private.Uri",
+    "version": "4.3.0",
+    "hash": "sha256-c5tXWhE/fYbJVl9rXs0uHh3pTsg44YD1dJvyOA0WoMs="
+  },
   {
     "pname": "System.Buffers",
     "version": "4.5.1",
     "hash": "sha256-wws90sfi9M7kuCPWkv1CEYMJtCqx9QB/kj0ymlsNaxI="
   },
+  {
+    "pname": "System.Buffers",
+    "version": "4.6.0",
+    "hash": "sha256-c2QlgFB16IlfBms5YLsTCFQ/QeKoS6ph1a9mdRkq/Jc="
+  },
   {
     "pname": "System.Collections.Immutable",
     "version": "8.0.0",
@@ -174,6 +214,11 @@
     "version": "5.0.0",
     "hash": "sha256-6mW3N6FvcdNH/pB58pl+pFSCGWgyaP4hfVtC/SMWDV4="
   },
+  {
+    "pname": "System.Diagnostics.DiagnosticSource",
+    "version": "8.0.1",
+    "hash": "sha256-zmwHjcJgKcbkkwepH038QhcnsWMJcHys+PEbFGC0Jgo="
+  },
   {
     "pname": "System.Formats.Asn1",
     "version": "6.0.0",
@@ -189,6 +234,11 @@
     "version": "4.2.13",
     "hash": "sha256-nkC/PiqE6+c1HJ2yTwg3x+qdBh844Z8n3ERWDW8k6Gg="
   },
+  {
+    "pname": "System.IO.Abstractions.TestingHelpers",
+    "version": "4.2.13",
+    "hash": "sha256-WGGatXlgyROnptdw0zU3ggf54eD/zusO/fvtf+5wuPU="
+  },
   {
     "pname": "System.IO.FileSystem.AccessControl",
     "version": "4.5.0",
@@ -204,16 +254,31 @@
     "version": "4.5.5",
     "hash": "sha256-EPQ9o1Kin7KzGI5O3U3PUQAZTItSbk9h/i4rViN3WiI="
   },
+  {
+    "pname": "System.Memory",
+    "version": "4.6.0",
+    "hash": "sha256-OhAEKzUM6eEaH99DcGaMz2pFLG/q/N4KVWqqiBYUOFo="
+  },
   {
     "pname": "System.Numerics.Vectors",
-    "version": "4.4.0",
-    "hash": "sha256-auXQK2flL/JpnB/rEcAcUm4vYMCYMEMiWOCAlIaqu2U="
+    "version": "4.6.0",
+    "hash": "sha256-fKS3uWQ2HmR69vNhDHqPLYNOt3qpjiWQOXZDHvRE1HU="
+  },
+  {
+    "pname": "System.Private.Uri",
+    "version": "4.3.0",
+    "hash": "sha256-fVfgcoP4AVN1E5wHZbKBIOPYZ/xBeSIdsNF+bdukIRM="
   },
   {
     "pname": "System.Reflection.Metadata",
     "version": "8.0.0",
     "hash": "sha256-dQGC30JauIDWNWXMrSNOJncVa1umR1sijazYwUDdSIE="
   },
+  {
+    "pname": "System.Runtime",
+    "version": "4.3.1",
+    "hash": "sha256-R9T68AzS1PJJ7v6ARz9vo88pKL1dWqLOANg4pkQjkA0="
+  },
   {
     "pname": "System.Runtime.CompilerServices.Unsafe",
     "version": "4.5.3",
@@ -224,6 +289,11 @@
     "version": "6.0.0",
     "hash": "sha256-bEG1PnDp7uKYz/OgLOWs3RWwQSVYm+AnPwVmAmcgp2I="
   },
+  {
+    "pname": "System.Runtime.CompilerServices.Unsafe",
+    "version": "6.1.0",
+    "hash": "sha256-NyqqpRcHumzSxpsgRDguD5SGwdUNHBbo0OOdzLTIzCU="
+  },
   {
     "pname": "System.Security.AccessControl",
     "version": "4.5.0",