Add diagnostics tests

Parser.Tests/DiagnosticExtensions.cs

@@ -0,0 +1,47 @@
+using System.Linq;
+
+namespace Parser.Tests
+{
+    public static class DiagnosticExtensions
+    {
+        public static bool IsEquivalentTo(this SyntaxDiagnostic[] actualSequence, params SyntaxDiagnostic[] expectedSequence)
+        {
+            if (actualSequence.Length != expectedSequence.Length)
+            {
+                return false;
+            }
+
+            var actualSorted = actualSequence.OrderBy(x => x.Position).ToArray();
+            var expectedSorted = expectedSequence.OrderBy(x => x.Position).ToArray();
+            for (var i = 0; i < expectedSequence.Length; i++)
+            {
+                var expected = expectedSequence[i];
+                var actual = actualSequence[i];
+                if (expected.Position != actual.Position)
+                {
+                    return false;
+                }
+
+                if (expected is MissingTokenSyntaxDiagnostic expectedMissingToken)
+                {
+                    if (!(actual is MissingTokenSyntaxDiagnostic actualMissingToken))
+                    {
+                        return false;
+                    }
+
+                    if (expectedMissingToken.Kind != actualMissingToken.Kind)
+                    {
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        }
+
+        public static MissingTokenSyntaxDiagnostic MissingToken(int position, TokenKind kind)
+        {
+            return new MissingTokenSyntaxDiagnostic(position, kind);
+        }
+    }
+}

Parser.Tests/MParserShould.cs

@@ -2,6 +2,8 @@
 
 namespace Parser.Tests
 {
+    using static DiagnosticExtensions;
+
     public class MParserShould
     {
         private static MParser GetSut(string text)
@@ -66,7 +68,7 @@ namespace Parser.Tests
             var sut = GetSut(text);
             var actual = sut.Parse();
             var diagnostics = actual.Root.GetDiagnostics();
-            Assert.Collection(actual.Diagnostics, item => Assert.Equal("Unexpected token 'SemicolonToken', expected 'IdentifierToken'.", item.Message));
+            Assert.True(diagnostics.IsEquivalentTo(MissingToken(4, TokenKind.IdentifierToken)));
         }
 
         [Fact]

Parser/MissingTokenSyntaxDiagnostic.cs

@@ -0,0 +1,13 @@
+namespace Parser
+{
+    public class MissingTokenSyntaxDiagnostic : SyntaxDiagnostic
+    {
+        public TokenKind Kind { get; }
+
+        public MissingTokenSyntaxDiagnostic(int position, TokenKind tokenKind)
+            : base(position)
+        {
+            Kind = tokenKind;
+        }
+    }
+}

Parser/SyntaxDiagnostic.cs

@@ -0,0 +1,23 @@
+namespace Parser
+{
+    public class SyntaxDiagnostic
+    {
+        public int Position { get; }
+
+        public static SyntaxDiagnostic From(Internal.TokenDiagnostic diagnostic, int Position)
+        {
+            switch (diagnostic)
+            {
+                case Internal.MissingTokenDiagnostic missingToken:
+                    return new MissingTokenSyntaxDiagnostic(Position, missingToken.Kind);
+            }
+
+            throw new System.ArgumentOutOfRangeException(nameof(diagnostic));
+        }
+
+        protected SyntaxDiagnostic(int position)
+        {
+            Position = position;
+        }
+    }
+}

Parser/SyntaxNode.cs

@@ -127,38 +127,6 @@ namespace Parser
         }
     }
     
-    public class SyntaxDiagnostic
-    {
-        public int Position { get; }
-
-        public static SyntaxDiagnostic From(Internal.TokenDiagnostic diagnostic, int Position)
-        {
-            switch (diagnostic)
-            {
-                case Internal.MissingTokenDiagnostic missingToken:
-                    return new MissingTokenSyntaxDiagnostic(Position, missingToken.Kind);
-            }
-
-            throw new System.ArgumentOutOfRangeException(nameof(diagnostic));
-        }
-
-        protected SyntaxDiagnostic(int position)
-        {
-            Position = position;
-        }
-    }
-
-    public class MissingTokenSyntaxDiagnostic : SyntaxDiagnostic
-    {
-        public TokenKind Kind { get; }
-
-        internal MissingTokenSyntaxDiagnostic(int position, TokenKind tokenKind)
-            : base(position)
-        {
-            Kind = tokenKind;
-        }
-    }
-    
     public abstract class StatementSyntaxNode : SyntaxNode
     {
         internal StatementSyntaxNode(SyntaxNode parent, Internal.GreenNode green, int position) : base(parent, green, position)