为什么使用HostType（“ Moles”）进行的单元测试中的断言在单独运行时可以通过，而在一组测试中运行时却失败？

Question

I recently got aboard the Pex & Moles bandwagon in order to test some logic with many elements that are static, non-virtual, sealed, etc. Recently, I've begun to see behavior I can't explain from a few of the tests.

A couple of the methods for an interface I stubbed out return void, so I set the stubs to delegates that update boolean variables to indicate that they've been called. Here's what I'm doing:

[TestMethod]
[HostType("Moles")]
    public void UnitTestX()
    {
        bool disposeCalled = false;
        bool getCalled = false;

        ClassX classX = new ClassX();
        var data = new SIClassXData
                       {
                           Dispose = () => disposeCalled = true,
                           Get = () => getCalled = true,
                           ClassXGet = () => classX
                       };

        MDataLayerFactory.CreateDataLayerObject(() => (IClassXData)data);

        Assert.IsTrue(disposeCalled);
        Assert.IsTrue(getCalled);
    }

For whatever reason, the asserts above succeed if I run this test alone. But if I run the test along with every other test in the assembly (using Visual Studio's "Run All Tests in Solution" capability), the first assert fails.

I'd like to know why this occurs, and what I need to change to resolve the issue.

Answer 1

Could it just be a side-effect of the 'run all tests' using multiple threads to execute the tests? So, that Dispose() has not run by the time the Assert fires?

Try using a ManualResetEvent to block the test method until Dispose() has run? Something like;

public void UnitTestX()
{
    // use this to block the test thread until Dispose() is run
    ManualResetEvent mre = new ManualResetEvent(false);

    bool disposeCalled = false;
    bool getCalled = false;

    ClassX classX = new ClassX();
    var data = new SIClassXData
                   {
                       Dispose = () => { 
                          disposeCalled = true; 
                          mre.Set(); // release the test thread now
                       },
                       Get = () => getCalled = true,
                       ClassXGet = () => classX
                   };

    MDataLayerFactory.CreateDataLayerObject(() => (IClassXData)data);

    Assert.IsTrue(mre.WaitOne(1000)); // give it a second to fire
    Assert.IsTrue(disposeCalled);
    Assert.IsTrue(getCalled);
}