xUnit1038 Error

There are more TheoryData type arguments than allowed by the parameters of the test method

Cause

When you use TheoryData with [MemberData], the number of generic types in TheoryData must match the number of parameters in the test method. In this case, you have provided too many types to TheoryData.

Reason for rule

You must provide the correct number of arguments to the test method to run the test.

How to fix violations

To fix a violation of this rule, either remove unused type arguments, or add more parameters.

Examples

Violates

using Xunit;

public class xUnit1038
{
    public static TheoryData<int, string> PropertyData =>
        new() { { 1, "Hello" }, { 2, "World" } };

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

Does not violate

using Xunit;

public class xUnit1038
{
    public static TheoryData<int> PropertyData =>
        new() { 1, 2, 3 };

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

using Xunit;

public class xUnit1038
{
    public static TheoryData<int, string> PropertyData =>
        new() { { 1, "Hello" }, { 2, "World" } };

    [Theory]
    [MemberData(nameof(PropertyData))]
    public void TestMethod(int _1, string _2) { }
}