xUnit1019 v2 v3 Error

MemberData must reference a member providing a valid data type

Cause

This rule is triggered when your [MemberData] attribute points to a member does not have a valid return type (IEnumerable<object[]> or something compatible with it, like TheoryData<>). For v3 tests, this also includes support for IAsyncEnumerable<> as well as supporting ITheoryDataRow in addition to object[] to represent a single row of data.

Reason for rule

[MemberData] attributes which do not point to valid data sources will fail at runtime.

How to fix violations

To fix a violation of this rule, update the data member to have an appropriate return type.

Using the types object[] or ITheoryRowData will trigger xUnit1042 because they are not strongly typed. It is strongly suggested that you choose to use TheoryData<> for v2/v3, or IEnumerable<TheoryDataRow<>>/IAsyncEnumerable<TheoryDataRow<>> for v3, as those provide compiler-level type safety and additional code analysis is possible to ensure the types of the test method parameters match the generic types of your theory data.

Examples

Violates

using System.Collections.Generic;
using Xunit;

public class xUnit1019
{
    public static IEnumerable<object> TestData;

    [Theory]
    [MemberData(nameof(TestData))]
    public void TestMethod(string greeting, int age) { }
}

Does not violate

For v2 and v3

using System.Collections.Generic;
using Xunit;

public class xUnit1019
{
    public static IEnumerable<object[]> TestData;

    [Theory]
    [MemberData(nameof(TestData))]
    public void TestMethod(string greeting, int age) { }
}

For v3 only

using System.Collections.Generic;
using Xunit;

public class xUnit1019
{
    public static IEnumerable<ITheoryDataRow> TestData;

    [Theory]
    [MemberData(nameof(TestData))]
    public void TestMethod(string greeting, int age) { }
}

using System.Collections.Generic;
using Xunit;

public class xUnit1019
{
    public static IAsyncEnumerable<object[]> TestData;

    [Theory]
    [MemberData(nameof(TestData))]
    public void TestMethod(string greeting, int age) { }
}

using System.Collections.Generic;
using Xunit;

public class xUnit1019
{
    public static IAsyncEnumerable<ITheoryDataRow> TestData;

    [Theory]
    [MemberData(nameof(TestData))]
    public void TestMethod(string greeting, int age) { }
}