Unit test runs only once with array as parameter

Question

I have two unit tests as follows:

    [DataTestMethod]
    [DataRow(1, 1, 2)]
    [DataRow(2, 2, 4)]
    [DataRow(3, 3, 6)]
    public void AddTest1(int x, int y, int expected)
    {
        Assert.AreEqual(expected, x + y);
    }


    [DataTestMethod]
    [DataRow(new int[] { 1, 2, 3, 4 }, new int[] { 1, 3, 6, 10 })]
    [DataRow(new int[] { 1, 1, 1, 1, 1 }, new int[] { 1, 2, 3, 4, 5 })]
    [DataRow(new int[] { 3, 1, 2, 10, 1 }, new int[] { 3, 4, 6, 16, 17 })]
    public void AddTest2(int[] input, int[] expectedOutput)
    {
        Assert.AreEqual(input[0], expectedOutput[0]);
    }

The first unit test runs 3 times, once for each data row. The second unit test only runs once for the first DataRow.

How can I run the second UnitTests with the arrays once for each DataRow as well?

Answer 1

Most test frameworks require the test cases to use compile-time constants as parameters.

This works because the parameters are constant at compile time:

[DataTestMethod]
[DataRow(1, 1, 2)]
[DataRow(2, 2, 4)]
[DataRow(3, 3, 6)]
public void AddTest1(int x, int y, int expected)
{
    Assert.AreEqual(expected, x + y);
}

This doesn't work because you're not using compile-time constants:

[DataTestMethod]
[DataRow(new int[] { 1, 2, 3, 4 }, new int[] { 1, 3, 6, 10 })]
[DataRow(new int[] { 1, 1, 1, 1, 1 }, new int[] { 1, 2, 3, 4, 5 })]
[DataRow(new int[] { 3, 1, 2, 10, 1 }, new int[] { 3, 4, 6, 16, 17 })]
public void AddTest2(int[] input, int[] expectedOutput)
{
    Assert.AreEqual(input[0], expectedOutput[0]);
}

The new keyword with an array doesn't allow the test framework to differentiate (looking at the image you linked, it just says System.Int32[]).

A workaround might be this:

[DataTestMethod]
[DataRow(0, new int[] { 1, 2, 3, 4 }, new int[] { 1, 3, 6, 10 })]
[DataRow(1, new int[] { 1, 1, 1, 1, 1 }, new int[] { 1, 2, 3, 4, 5 })]
[DataRow(2, new int[] { 3, 1, 2, 10, 1 }, new int[] { 3, 4, 6, 16, 17 })]
public void AddTest2(int run, int[] input, int[] expectedOutput)
{
    Assert.AreEqual(input[0], expectedOutput[0]);
}

That way, the different test cases can be differentiated by a compile-time constant.