Fix filter bug (#322)

WoofWare.NUnitTestRunner.Lib/Filter.fs

@@ -108,7 +108,8 @@ module internal Lexer =
                         i <- i + 1
                     | _ ->
                         yield Token.single TokenType.Not startI 1
-                        i <- i + 1
+                        // Don't advance i here - we only consumed the '!' character
+                        ()
                 | Token.SingleChar token, State.Awaiting ->
                     i <- i + 1
                     yield token
@@ -162,7 +163,7 @@ module internal ParsedFilter =
 
         match token.Type with
         | TokenType.QuotedString ->
-            // +1 and -1, because the trivia contains the initial and terminal quote mark
+            // +1 to skip the initial quote; len includes the initial quote but excludes the terminal quote
             inputString.Substring (start + 1, len - 1)
             |> unescape
             |> ParsedFilter.String

WoofWare.NUnitTestRunner/WoofWare.NUnitTestRunner.Test/TestFilter.fs

@@ -123,3 +123,15 @@ module TestFilter =
     [<TestCaseSource(nameof xmlExamples)>]
     let ``XML examples`` (example : string, expected : Filter) =
         Filter.parse example |> shouldEqual expected
+
+    let negationExamples =
+        [
+            "!Name=foo", Filter.Not (Filter.Name (Match.Exact "foo"))
+            "!FullyQualifiedName=bar", Filter.Not (Filter.FullyQualifiedName (Match.Exact "bar"))
+            "!TestCategory=baz", Filter.Not (Filter.TestCategory (Match.Exact "baz"))
+        ]
+        |> List.map TestCaseData
+
+    [<TestCaseSource(nameof negationExamples)>]
+    let ``Negation examples`` (example : string, expected : Filter) =
+        Filter.parse example |> shouldEqual expected