Use AutoData and MemberData attributes in XUnit test

Question

I'm facing an interesting problem. I found out that the AutoDataAttribute can be use to minimize the "Arrange" part of your test (dependencies passed through the ctor). Awesome!

Example:

public class AutoMoqDataAttribute : AutoDataAttribute
{
    public AutoMoqDataAttribute()
        : base(new Fixture().Customize(new AutoMoqCustomization()))
    { }
}

[Theory, AutoMoqData]
public void Process_ValidContext_CallsK2Workflows(
    [Frozen]Mock<IK2Datasource> k2,
    [Frozen]Mock<IAppConfiguration> config,
    PrBatchApproveBroker sut)
{
   (...)
}

Now i want to use this great feature and inject my own data into this theory:

[Theory, AutoMoqData, MemberData("Data")]
public void ExtractPayments_EmptyInvoiceNumber_IgnoresRecordsWithEmptyInvoiceNumber(
        [Frozen]Mock<IExcelDatasource> xls,
        SunSystemExcelDatasource sut,
        List<Row> rows,
        int expectedCount)
{
    (...)
}

Problem: AutoData attribute will generate random data for me. The only way I found is to get rid of the AutoData attribute and use MemberData. If I do that, I need to handle object instantiations myself :)...

Is there a way to pass my classes and some "hard-coded" data at the same time?

Thank u, Seb

Answer 1

Is there a way to pass my classes and some "hard-coded" data at the same time?

One way of doing that is by supplying some inline values through the attribute, and have AutoFixture fill the rest of them.

[Theory, InlineAutoMoqData(3)]
public void ExtractPayments_EmptyInvoiceNumber_IgnoresRecordsWithEmptyInvoiceNumber(
    int expectedCount,
    [Frozen]Mock<IExcelDatasource> xls,
    SunSystemExcelDatasource sut,
    List<Row> rows)
{
    // expectedCount is 3.
}

Note that I had to move expectedCount in order to be the first parameter, and make use of a custom InlineAutoMoqData attribute defined as:

internal class AutoMoqDataAttribute : AutoDataAttribute
{
    internal AutoMoqDataAttribute()
        : base(new Fixture().Customize(new AutoMoqCustomization()))
    {
    }
}

internal class InlineAutoMoqDataAttribute : CompositeDataAttribute
{
    internal InlineAutoMoqDataAttribute(params object[] values)
        : base(
              new DataAttribute[] { 
                  new InlineDataAttribute(values),
                  new AutoMoqDataAttribute() })
    {
    }
}

See also this post and this one for some other examples.

Answer 2

You will have to create your own custom DataAttribute. This is how you can compose.

/// <summary>
/// Helper DataAttribute to use the regular xUnit based DataAttributes with AutoFixture and Mocking capabilities.
/// </summary>
/// <seealso cref="Xunit.Sdk.DataAttribute" />
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public class AutoCompositeDataAttribute : DataAttribute
{
    /// <summary>
    /// The attributes
    /// </summary>
    private readonly DataAttribute baseAttribute;

    /// <summary>
    /// The automatic data attribute
    /// </summary>
    private readonly DataAttribute autoDataAttribute;

    /// <summary>
    /// Initializes a new instance of the <see cref="AutoCompositeDataAttribute" /> class.
    /// </summary>
    /// <param name="baseAttribute">The base attribute.</param>
    /// <param name="autoDataAttribute">The automatic data attribute.</param>
    public AutoCompositeDataAttribute(DataAttribute baseAttribute, DataAttribute autoDataAttribute)
    {
        this.baseAttribute = baseAttribute;
        this.autoDataAttribute = autoDataAttribute;
    }

    /// <summary>
    /// Returns the data to be used to test the theory.
    /// </summary>
    /// <param name="testMethod">The method that is being tested</param>
    /// <returns>
    /// One or more sets of theory data. Each invocation of the test method
    /// is represented by a single object array.
    /// </returns>
    public override IEnumerable<object[]> GetData(MethodInfo testMethod)
    {
        if (testMethod == null)
        {
            throw new ArgumentNullException(nameof(testMethod));
        }

        var data = this.baseAttribute.GetData(testMethod);

        foreach (var datum in data)
        {
            var autoData = this.autoDataAttribute.GetData(testMethod).ToArray()[0];

            for (var i = 0; i < datum.Length; i++)
            {
                autoData[i] = datum[i];
            }

            yield return autoData;
        }
    }
}



/// <summary>
/// Member auto data implementation based on InlineAutoDataAttribute and MemberData
/// </summary>
/// <seealso cref="Ploeh.AutoFixture.Xunit2.CompositeDataAttribute" />
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public class MemberAutoDataAttribute : AutoCompositeDataAttribute
{
    /// <summary>
    /// The automatic data attribute
    /// </summary>
    private readonly AutoDataAttribute autoDataAttribute;

    /// <summary>
    /// Initializes a new instance of the <see cref="MemberAutoDataAttribute" /> class.
    /// </summary>
    /// <param name="memberName">Name of the member.</param>
    /// <param name="parameters">The parameters.</param>
    public MemberAutoDataAttribute(string memberName, params object[] parameters)
        : this(new AutoDataAttribute(), memberName, parameters)
    {
    }

    /// <summary>
    /// Initializes a new instance of the <see cref="MemberAutoDataAttribute" /> class.
    /// </summary>
    /// <param name="autoDataAttribute">The automatic data attribute.</param>
    /// <param name="memberName">Name of the member.</param>
    /// <param name="parameters">The parameters.</param>
    public MemberAutoDataAttribute(AutoDataAttribute autoDataAttribute, string memberName, params object[] parameters)
        : base((DataAttribute)new MemberDataAttribute(memberName, parameters), (DataAttribute)autoDataAttribute)
    {
        this.autoDataAttribute = autoDataAttribute;
    }

    /// <summary>
    /// Gets the automatic data attribute.
    /// </summary>
    /// <value>
    /// The automatic data attribute.
    /// </value>
    public AutoDataAttribute AutoDataAttribute => this.autoDataAttribute;
}

If you want to enable Moq, then extend this to get

/// <summary>
/// The member auto moq data attribute.
/// </summary>
[AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
public class MemberAutoMoqDataAttribute : MemberAutoDataAttribute
{
    /// <summary>
    /// Initializes a new instance of the <see cref="MemberAutoMoqDataAttribute"/> class.
    /// </summary>
    /// <param name="memberName">Name of the member.</param>
    /// <param name="parameters">The parameters.</param>
    public MemberAutoMoqDataAttribute(string memberName, params object[] parameters)
        : base(new AutoMoqDataAttribute(), memberName, parameters)
    {
    }
}