xUnit1040 Warning

The type argument to TheoryData is nullable, while the type of the corresponding test method parameter is not

Cause

The TheoryData type argument is marked as nullable, and the test method argument is marked as non-nullable.

Reason for rule

Passing null data to a test method that isn’t expecting it could cause runtime errors or unpredictable test results (either false positives or false negatives).

How to fix violations

To fix a violation of this rule, either make the TheoryData type non-nullable, or make the test method parameter nullable.

Examples

Violates

using Xunit;

public class xUnit1040
{
    public static TheoryData<string?> PropertyData =>
        new() { "Hello", "World", null };

    [Theory]
    [MemberData(nameof(PropertyData))]
    public void TestMethod(string _) { }
}

Does not violate

using Xunit;

public class xUnit1040
{
    public static TheoryData<string> PropertyData =>
        new() { "Hello", "World" };

    [Theory]
    [MemberData(nameof(PropertyData))]
    public void TestMethod(string _) { }
}

using Xunit;

public class xUnit1040
{
    public static TheoryData<string?> PropertyData =>
        new() { "Hello", "World", null };

    [Theory]
    [MemberData(nameof(PropertyData))]
    public void TestMethod(string? _) { }
}