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Fix MSTEST0037 to detect LINQ Enumerable.Contains on interface types #7487

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Merged
Evangelink merged 2 commits into from
Mar 6, 2026
+297 −1
Merged

Fix MSTEST0037 to detect LINQ Enumerable.Contains on interface types #7487

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ecc0581
Fix MSTEST0037 to detect LINQ Enumerable.Contains on interface types
Evangelink Mar 3, 2026
aed8879
Rename test
Evangelink Mar 4, 2026
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16 changes: 15 additions & 1 deletion src/Analyzers/MSTest.Analyzers/UseProperAssertMethodsAnalyzer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -493,6 +493,7 @@ private static StringMethodCheckStatus RecognizeStringMethodCheck(
private static CollectionCheckStatus RecognizeCollectionMethodCheck(
IOperation operation,
INamedTypeSymbol objectTypeSymbol,
INamedTypeSymbol? enumerableTypeSymbol,
out SyntaxNode? collectionExpression,
out SyntaxNode? itemExpression)
{
Expand Down Expand Up @@ -527,6 +528,19 @@ private static CollectionCheckStatus RecognizeCollectionMethodCheck(
}
}
}

// Handle LINQ Enumerable.Contains<TSource>(this IEnumerable<TSource>, TSource)
// In the Roslyn operation model, LINQ extension calls appear with ContainingType == Enumerable
// and Arguments includes the 'this' parameter, so Arguments.Length == 2.
if (methodName == "Contains" &&
invocation.Arguments.Length == 2 &&
enumerableTypeSymbol is not null &&
SymbolEqualityComparer.Default.Equals(invocation.TargetMethod.ContainingType, enumerableTypeSymbol))
{
collectionExpression = invocation.Arguments[0].Value.Syntax;
itemExpression = invocation.Arguments[1].Value.Syntax;
return CollectionCheckStatus.Contains;
}
}

collectionExpression = null;
Expand Down Expand Up @@ -748,7 +762,7 @@ private static void AnalyzeIsTrueOrIsFalseInvocation(OperationAnalysisContext co
}

// Check for collection method patterns: myCollection.Contains(...)
CollectionCheckStatus collectionMethodStatus = RecognizeCollectionMethodCheck(conditionArgument, objectTypeSymbol, out SyntaxNode? collectionExpr, out SyntaxNode? itemExpr);
CollectionCheckStatus collectionMethodStatus = RecognizeCollectionMethodCheck(conditionArgument, objectTypeSymbol, enumerableTypeSymbol, out SyntaxNode? collectionExpr, out SyntaxNode? itemExpr);
if (collectionMethodStatus != CollectionCheckStatus.Unknown)
{
if (collectionMethodStatus == CollectionCheckStatus.Contains)
Expand Down
282 changes: 282 additions & 0 deletions test/UnitTests/MSTest.Analyzers.UnitTests/UseProperAssertMethodsAnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3853,4 +3853,286 @@ await VerifyCS.VerifyCodeFixAsync(
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("IsNull", "AreEqual"),
fixedCode);
}

#region LINQ Enumerable.Contains on interface types

[TestMethod]
public async Task WhenAssertIsTrueWithLinqContainsOnIReadOnlyList()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
{|#0:Assert.IsTrue(list.Contains(2))|};
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
Assert.Contains(2, list);
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("Contains", "IsTrue"),
fixedCode);
}

[TestMethod]
public async Task WhenAssertIsFalseWithLinqContainsOnIReadOnlyList()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
{|#0:Assert.IsFalse(list.Contains(4))|};
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
Assert.DoesNotContain(4, list);
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("DoesNotContain", "IsFalse"),
fixedCode);
}

[TestMethod]
public async Task WhenAssertIsTrueWithLinqContainsOnIEnumerable()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IEnumerable<string> items = new List<string> { "a", "b", "c" };
{|#0:Assert.IsTrue(items.Contains("b"))|};
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IEnumerable<string> items = new List<string> { "a", "b", "c" };
Assert.Contains("b", items);
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("Contains", "IsTrue"),
fixedCode);
}

[TestMethod]
public async Task WhenAssertIsTrueWithLinqContainsOnIReadOnlyList_WithMessage()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
{|#0:Assert.IsTrue(list.Contains(2),
"should contain the value")|};
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyList<int> list = new List<int> { 1, 2, 3 };
Assert.Contains(2, list,
"should contain the value");
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("Contains", "IsTrue"),
fixedCode);
}

[TestMethod]
public async Task WhenAssertIsTrueWithLinqContainsOnIReadOnlyCollection()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyCollection<int> items = new List<int> { 1, 2, 3 };
{|#0:Assert.IsTrue(items.Contains(2))|};
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
IReadOnlyCollection<int> items = new List<int> { 1, 2, 3 };
Assert.Contains(2, items);
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("Contains", "IsTrue"),
fixedCode);
}

[TestMethod]
public async Task WhenAssertIsTrueWithLinqContainsOnCustomNonBCLCollection_Reports()
{
string code = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
var custom = new MyCustomCollection<int>(new[] { 1, 2, 3 });
{|#0:Assert.IsTrue(custom.Contains(2))|};
}

internal sealed class MyCustomCollection<T> : IEnumerable<T>
{
private readonly IEnumerable<T> _items;
public MyCustomCollection(IEnumerable<T> items) => _items = items;
public IEnumerator<T> GetEnumerator() => _items.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
}
""";

string fixedCode = """
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

[TestClass]
public class MyTestClass
{
[TestMethod]
public void MyTestMethod()
{
var custom = new MyCustomCollection<int>(new[] { 1, 2, 3 });
Assert.Contains(2, custom);
}

internal sealed class MyCustomCollection<T> : IEnumerable<T>
{
private readonly IEnumerable<T> _items;
public MyCustomCollection(IEnumerable<T> items) => _items = items;
public IEnumerator<T> GetEnumerator() => _items.GetEnumerator();
IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}
}
""";

await VerifyCS.VerifyCodeFixAsync(
code,
VerifyCS.DiagnosticIgnoringAdditionalLocations().WithLocation(0).WithArguments("Contains", "IsTrue"),
fixedCode);
}

#endregion
}