Unit test for two string arrays

Question

The below data row in my unit test throws an error message when two string arrays follow after one another, but not when I place another data type in-between.

[TestClass]
public class UnitTest
{
    [TestMethod]
    // invalid
    [DataRow(new string[] { }, new string[] { })]
    // valid
    [DataRow(new string[] { }, 8, new string[] { })]
    public void TestMethod(string[] input, string[] output)
    {
        var solution = new Program();

        CollectionAssert.AreEqual(output, solution.Method(input));
    }
}

And I get the following error (on line 6), an attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type. I'm defining the array in constructor, so how is it not constant? Thank you in advance.