test: add parser and lexer error message tests

test/Gridify.Tests/ErrorMessageTests.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using System.Linq;
+using Gridify.Syntax;
 using Xunit;
 using Xunit.Abstractions;
 
@@ -35,7 +36,32 @@ public void FilteringError_WhenInvalidCharacterDetected_ShouldReturnErrorWithCha
       // assert
       var exception = Assert.Throws<GridifyFilteringException>(act);
       _testOutputHelper.WriteLine(exception.Message);
-      Assert.Contains($"at index {index.ToString()}", exception.Message);
+      Assert.Contains($", at index {index.ToString()}", exception.Message);
       Assert.Contains("bad character input", exception.Message);
    }
+
+   [Theory]
+   [InlineData("test=(1234)", 5, SyntaxKind.OpenParenthesisToken, SyntaxKind.ValueToken)]
+   [InlineData("test(=123", 4, SyntaxKind.OpenParenthesisToken, SyntaxKind.Operator)]
+   [InlineData("(test=2", 7, SyntaxKind.End, SyntaxKind.CloseParenthesis)]
+   [InlineData("test=,", 6, SyntaxKind.End, SyntaxKind.FieldToken)] // test=, is valid if there is another expression after <AND> operator
+   [InlineData("test=2,2", 7, SyntaxKind.BadToken, SyntaxKind.FieldToken)]
+   public void FilteringError_WhenInvalidTokenDetected_ShouldReturnErrorWithExpectedToken(
+      string filter,
+      int index,
+      SyntaxKind unexpectedToken,
+      SyntaxKind expectedToken)
+   {
+      // arrange
+      var dataSource = new List<TestClass>().AsQueryable();
+      var gq = new GridifyQuery() { Filter = filter };
+
+      // act
+      var act = () => dataSource.ApplyFiltering(gq);
+
+      // assert
+      var exception = Assert.Throws<GridifyFilteringException>(act);
+      _testOutputHelper.WriteLine(exception.Message);
+      Assert.Contains($"Unexpected token <{unexpectedToken}> at index {index}, expected <{expectedToken}>", exception.Message);
+   }
 }