v2 v3   Warning

xUnit1034

"Null should only be used for nullable parameters"

Cause

When you use [MemberData] to target a method and pass that method arguments, the values must match the nullability of the method parameters (that is, null values are not allowed to be passed to non-nullable parameters of the method data function).

Reason for rule

Passing null values to functions that aren't expecting them can be cause for runtime errors.

How to fix violations

To fix a violation of this rule, either replace the null argument with a non-null value, or update the parameter to accept a nullable value.

Examples

Violates

using Xunit;

public class xUnit1034
{
    public static TheoryData<string> TestData(int n, string s) =>
        new() { $"Hello {s}! x {n}" };

    [Theory]
    [MemberData(nameof(TestData), 2112, null)]
    public void TestMethod(string _)
    { }
}

Does not violate

using Xunit;

public class xUnit1034
{
    public static TheoryData<string> TestData(int n, string s) =>
        new() { $"Hello {s}! x {n}" };

    [Theory]
    [MemberData(nameof(TestData), 2112, "Brad")]
    public void TestMethod(string _)
    { }
}

using Xunit;

public class xUnit1034
{
    public static TheoryData<string> TestData(int n, string? s) =>
        new() { $"Hello {s ?? "friend"}! x {n}" };

    [Theory]
    [MemberData(nameof(TestData), 2112, null)]
    public void TestMethod(string _)
    { }
}