xUnit1007 v2 v3 Error

ClassData must point at a valid class

Cause

The type referenced by the [ClassData] attribute does not implement IEnumerable<object[]> or does not have a public parameterless constructor. For v3 projects, the class may also implement IAsyncEnumerable<object[]>, IEnumerable<ITheoryDataRow>, or IAsyncEnumerable<ITheoryDataRow>.

Reason for rule

xUnit.net will attempt to instantiate and enumerate the type specified in [ClassData] in order to retrieve test data for the theory. In order for instantiation to succeed, there must be a public parameterless constructor. In order for enumeration to work, the type must implement IEnumerable<object[]>.

How to fix violations

To fix a violation of this rule, make sure that the type specified in the [ClassData] attribute meets all of these requirements:

Is a class or a struct type.
Implements IEnumerable<object[]>.
Defines a public parameterless constructor. (The C# and VB.NET compilers will implicitly provide a suitable default constructor if you do not define any constructors at all.)

Examples

Violates

using Xunit;

class xUnit1007_TestData { }

public class xUnit1007
{
    [Theory]
    [ClassData(typeof(xUnit1007_TestData))]
    public void TestMethod(int quantity, string productType)
    { }
}

Does not violate

For v2 and v3

using System.Collections;
using System.Collections.Generic;
using Xunit;

class xUnit1007_TestData : IEnumerable<object[]>
{
    public IEnumerator<object[]> GetEnumerator()
    {
        yield return new object[] { 12, "book" };
        yield return new object[] { 9, "magnifying glass" };
    }

    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
}

public class xUnit1007
{
    [Theory]
    [ClassData(typeof(xUnit1007_TestData))]
    public void TestMethod(int quantity, string productType)
    { }
}

For v3 only

using System.Collections.Generic;
using System.Threading;
using Xunit;

class xUnit1007_TestData : IAsyncEnumerable<object[]>
{
    public async IAsyncEnumerator<object[]> GetAsyncEnumerator(CancellationToken cancellationToken = default)
    {
        yield return new object[] { 12, "book" };
        yield return new object[] { 9, "magnifying glass" };
    }
}

public class xUnit1007
{
    [Theory]
    [ClassData(typeof(xUnit1007_TestData))]
    public void TestMethod(int quantity, string productType)
    { }
}

using System.Collections;
using System.Collections.Generic;
using Xunit;

class xUnit1007_TestData : IEnumerable<TheoryDataRow<int, string>>
{
    public IEnumerator<TheoryDataRow<int, string>> GetEnumerator()
    {
        yield return new TheoryDataRow<int, string>(12, "book");
        yield return new TheoryDataRow<int, string>(9, "magnifying glass");
    }

    IEnumerator IEnumerable.GetEnumerator() => throw new System.NotImplementedException();
}

public class xUnit1007
{
    [Theory]
    [ClassData(typeof(xUnit1007_TestData))]
    public void TestMethod(int quantity, string productType)
    { }
}

using System.Collections.Generic;
using System.Threading;
using Xunit;

class xUnit1007_TestData : IAsyncEnumerable<TheoryDataRow<int, string>>
{
    public async IAsyncEnumerator<TheoryDataRow<int, string>> GetAsyncEnumerator(CancellationToken cancellationToken = default)
    {
        yield return new TheoryDataRow<int, string>(12, "book");
        yield return new TheoryDataRow<int, string>(9, "magnifying glass");
    }
}

public class xUnit1007
{
    [Theory]
    [ClassData(typeof(xUnit1007_TestData))]
    public void TestMethod(int quantity, string productType)
    { }
}