Allow overriding snapshot formatting (#9)

WoofWare.Expect.Test/SimpleTest.fs

@@ -1,5 +1,8 @@
 namespace WoofWare.Expect.Test
 
+open System.Collections.Generic
+open System.Text.Json
+open System.Text.Json.Serialization
 open WoofWare.Expect
 open NUnit.Framework
 
@@ -41,3 +44,133 @@ actual was:
             snapshot @"123"
             return 123
         }
+
+    [<Test>]
+    let ``Formatting example`` () =
+        expect {
+            withFormat (fun x -> x.GetType().Name)
+            snapshot @"Int32"
+            return 123
+        }
+
+        expect {
+            snapshot @"Int32"
+            withFormat (fun x -> x.GetType().Name)
+            return 123
+        }
+
+    [<Test>]
+    let ``Custom JSON output`` () =
+        // 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:
+
+- [JSON failed to parse:] {
+-     // a key here
+-     ""a"":3
+- }
+
+actual was:
+
++ {
++   ""a"": 3
++ }"
+
+            return
+                Assert.Throws<ExpectException> (fun () ->
+                    expectWithMockedFilePath ("file.fs", 99) {
+                        snapshotJson
+                            @"{
+    // a key here
+    ""a"":3
+}"
+
+                        return Map.ofList [ "a", 3 ]
+                    }
+                )
+                |> _.Message
+        }
+
+        // but it can be made to like them!
+        expect {
+            snapshotJson
+                @"{
+                // a key here
+                ""a"":3
+            }"
+
+            withJsonDocOptions (JsonDocumentOptions (CommentHandling = JsonCommentHandling.Skip))
+            return Map.ofList [ "a", 3 ]
+        }
+
+    type SomeDu =
+        | Something of IReadOnlyDictionary<string, string>
+        | SomethingElse of string
+
+    type MoreComplexType =
+        {
+            Thing : int
+            SomeDu : SomeDu option
+        }
+
+    [<Test>]
+    let ``JSON snapshot of complex ADT`` () =
+        expect {
+            snapshotJson
+                @"{
+  ""SomeDu"": {
+    ""Case"": ""Something"",
+    ""Fields"": [
+      {
+        ""hi"": ""bye""
+      }
+    ]
+  },
+  ""Thing"": 3,
+}"
+
+            return
+                {
+                    Thing = 3
+                    SomeDu = Some (SomeDu.Something (Map.ofList [ "hi", "bye" ]))
+                }
+        }
+
+    [<Test>]
+    let ``Overriding JSON format, from docstring`` () =
+        expect {
+            snapshotJson @"{""a"":3}"
+            withJsonSerializerOptions (JsonSerializerOptions (WriteIndented = false))
+            return Map.ofList [ "a", 3 ]
+        }
+
+    [<Test>]
+    let ``Overriding the JSON format`` () =
+        expect {
+            snapshotJson
+                @"{
+  ""Thing"": 3,
+  ""SomeDu"": [
+    ""Some"",
+    [
+      ""Something"",
+      {
+        ""hi"": ""bye""
+      }
+    ]
+  ]
+}"
+
+            withJsonSerializerOptions (
+                let options = JsonFSharpOptions.ThothLike().ToJsonSerializerOptions ()
+                options.WriteIndented <- true
+                options
+            )
+
+            return
+                {
+                    Thing = 3
+                    SomeDu = Some (SomeDu.Something (Map.ofList [ "hi", "bye" ]))
+                }
+        }