C# DeploymentItem fails to copy file for MSTest unit test

Question

I'm having trouble getting an XSL file to be copied to the same directory as the test assembly when I use the DeploymentItem attribute on an MSTest unit test. I followed the chosen answer for this question and the file I need copied has its "Copy to Output Directory" set to "Copy Always". When I check my ProjectDir\bin directory (the Target directory), the file I want copied is indeed there, alongside the DLLs and PDBs.

I have a couple unit tests with the following setup:

private const string DLL = "Service.dll";
private const string XSL_PATH = "transform.xsl";

[TestInitialize]
public void InitializeTest()
{
    Assert.IsTrue(File.Exists(DLL)); // passes
}

[TestMethod]
[DeploymentItem(DLL)]
[DeploymentItem(XSL_PATH)]
public void XmlToResultsTest()
{
    Assert.IsTrue(File.Exists(XSL_PATH)); // fails
}

The XSL test fails because when I check MSTest's TestResults\particularTestRun\Out directory, I see the DLLs and the PDBs, but my XSL file is not there. What I want to know is why the XSL file does not get copied alongside the DLLs and PDBs even when I explicitly tell Visual Studio to copy it there via DeploymentItem?

Answer 1

Thanks to Marc Gravell's answer to a related question of mine, I tried updating my MSTest .testrunconfig file so that my XSL file is included in the 'Deployment' section. This lets my unit tests pass, but I'm still perturbed that I had to do this--shouldn't the combination of DeploymentItem and marking the file's properties in my project to copy to the output directory be sufficient?