Handling exceptions in assembly-level setup methods in MbUnit

Posted at 07:00 on 04 May 2009

MbUnit allows you to run assembly-level setup and teardown methods as part of your unit tests using the AssemblyCleanUpAttribute:

[assembly: AssemblyCleanUp(typeof(AssemblyCleaner))]
public class AssemblyCleaner
{
    [SetUp]
    public static void SetUp()
    {
        // blah
    }
    [TearDown]
    public static void TearDown()
    {
        // blah
    }
}

This is very useful if you want to do something like restore your database to a known configuration, perhaps incorporating all your change scripts into your unit tests. Unfortunately, there is a little gotcha. If your SetUp() method throws an exception, none of your unit tests will run, but MbUnit will still report success.

For what it's worth, I think this is a bug, not a feature, but there is a way round it. Capture any exception, and create a unit test that re-throws it:

[assembly: AssemblyCleanUp(typeof(AssemblyCleaner))]
 
public class AssemblyCleaner
{
    private static Exception setupException = null;
 
    [SetUp]
    public static void SetUp()
    {
        try {
            // blah
        }
        catch (Exception ex) {
            setupException = ex;
        }
    }
 
    [TearDown]
    public static void TearDown()
    {
        // blah
    }
 
    internal static void RethrowSetupException()
    {
        if (setupException != null) {
            // Wrap the original exception to preserve its stack trace
            throw new InvalidOperationException(
                "An error occurred when setting up the tests",
                setupException);
        }
    }
}
 
// You need to have your unit tests in a separate class.
// MbUnit doesn't like you including test fixtures
// in your assembly cleanup class.
 
[TestFixture]
public class AssemblyCleanerTest
{
    [Test]
    public void ReportSetupException()
    {
        AssemblyCleaner.RethrowSetupException()
    }
}