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fix: #4807 xUnit Assert.Contains predicate parameter transposition #4813

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thomhurst merged 2 commits into from
Feb 15, 2026
Merged

fix: #4807 xUnit Assert.Contains predicate parameter transposition #4813

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dc534d8
Fix xUnit Assert.Contains parameter transposition bug
ascott18 Feb 15, 2026
46a8468
handles DoesNotContain
ascott18 Feb 15, 2026
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32 changes: 26 additions & 6 deletions TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -161,8 +161,8 @@ private bool IsXUnitAssertion(InvocationExpressionSyntax invocation)
"Empty" => ConvertEmpty(arguments),
"NotEmpty" => ConvertNotEmpty(arguments),
"Single" => ConvertSingle(arguments),
"Contains" => ConvertContains(arguments),
"DoesNotContain" => ConvertDoesNotContain(arguments),
"Contains" => ConvertContains(memberAccess, arguments),
"DoesNotContain" => ConvertDoesNotContain(memberAccess, arguments),
"Throws" => ConvertThrows(memberAccess, arguments),
"ThrowsAsync" => ConvertThrowsAsync(memberAccess, arguments),
"ThrowsAny" => ConvertThrowsAny(memberAccess, arguments),
Expand Down Expand Up @@ -321,23 +321,43 @@ private bool IsXUnitAssertion(InvocationExpressionSyntax invocation)
return (AssertionConversionKind.Single, $"await Assert.That({collection}).HasSingleItem()", true, null);
}

private (AssertionConversionKind, string?, bool, string?) ConvertContains(SeparatedSyntaxList<ArgumentSyntax> args)
private (AssertionConversionKind, string?, bool, string?) ConvertContains(MemberAccessExpressionSyntax memberAccess, SeparatedSyntaxList<ArgumentSyntax> args)
{
if (args.Count < 2) return (AssertionConversionKind.Contains, null, false, null);

var expected = args[0].Expression.ToString();
var collection = args[1].Expression.ToString();
var actual = args[1].Expression.ToString();

var symbol = SemanticModel.GetSymbolInfo(memberAccess).Symbol;

if (symbol is IMethodSymbol { Parameters.Length: 2 } methodSymbol &&
methodSymbol.Parameters[0].Type.Name == "IEnumerable" &&
methodSymbol.Parameters[1].Type.Name == "Predicate")
{
// Swap them - This overload is the other way around to the other ones.
(actual, expected) = (expected, actual);
}

return (AssertionConversionKind.Contains, $"await Assert.That({collection}).Contains({expected})", true, null);
return (AssertionConversionKind.Contains, $"await Assert.That({actual}).Contains({expected})", true, null);
}

private (AssertionConversionKind, string?, bool, string?) ConvertDoesNotContain(SeparatedSyntaxList<ArgumentSyntax> args)
private (AssertionConversionKind, string?, bool, string?) ConvertDoesNotContain(MemberAccessExpressionSyntax memberAccess, SeparatedSyntaxList<ArgumentSyntax> args)
{
if (args.Count < 2) return (AssertionConversionKind.DoesNotContain, null, false, null);

var expected = args[0].Expression.ToString();
var collection = args[1].Expression.ToString();

var symbol = SemanticModel.GetSymbolInfo(memberAccess).Symbol;

if (symbol is IMethodSymbol { Parameters.Length: 2 } methodSymbol &&
methodSymbol.Parameters[0].Type.Name == "IEnumerable" &&
methodSymbol.Parameters[1].Type.Name == "Predicate")
{
// Swap them - This overload is the other way around to the other ones.
(collection, expected) = (expected, collection);
}

return (AssertionConversionKind.DoesNotContain, $"await Assert.That({collection}).DoesNotContain({expected})", true, null);
}

Expand Down
72 changes: 72 additions & 0 deletions TUnit.Analyzers.Tests/XUnitMigrationAnalyzerTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2096,6 +2096,78 @@ public async Task GenericTest()
);
}

[Test]
public async Task XUnit_Assert_Contains_Predicate_Overload_Converted()
{
await CodeFixer
.VerifyCodeFixAsync(
"""
{|#0:using Xunit;

public class MyClass
{
[Fact]
public void MyTest()
{
var numbers = new[] { 22, 75, 19 };
Assert.Contains(numbers, x => x == 22);
}
}|}
""",
Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0),
"""
using System.Threading.Tasks;

public class MyClass
{
[Test]
public async Task MyTest()
{
var numbers = new[] { 22, 75, 19 };
await Assert.That(numbers).Contains(x => x == 22);
}
}
""",
ConfigureXUnitTest
);
}

[Test]
public async Task XUnit_Assert_DoesNotContain_Predicate_Overload_Converted()
{
await CodeFixer
.VerifyCodeFixAsync(
"""
{|#0:using Xunit;

public class MyClass
{
[Fact]
public void MyTest()
{
var numbers = new[] { 22, 75, 19 };
Assert.DoesNotContain(numbers, x => x == 22);
}
}|}
""",
Verifier.Diagnostic(Rules.XunitMigration).WithLocation(0),
"""
using System.Threading.Tasks;

public class MyClass
{
[Test]
public async Task MyTest()
{
var numbers = new[] { 22, 75, 19 };
await Assert.That(numbers).DoesNotContain(x => x == 22);
}
}
""",
ConfigureXUnitTest
);
}

private static void ConfigureXUnitTest(Verifier.Test test)
{
var globalUsings = ("GlobalUsings.cs", SourceText.From("global using Xunit;"));
Expand Down
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