Unit Testing a class with an internal constructor

Question

I have a class called "Session" which exposes several public methods. I'd like to Unit Test these, however in production I need to control instantiation of "Session" objects, so delegate construction to to a SessionManager class and have made the Session's constructor internal.

I'd ideally like to test the Session class in isolation from the SessionManager which creates it/them to prove that the public interfaces exposed by the Session work as expected - but can't instantiate a Session from a test without using a SessionManager making my tests more complicated/less useful than they need to be.

What's the best way to deal with this?

Cheers,

Lenny.

Answer 1

Nothing prevents you from testing internals. Simply make the internals of your code visible to the test suite, by using the InternalsVisibleTo attribute: in the AssemblyInfo, add

[assembly:InternalsVisibleTo("TestSuiteAssembly")]

Answer 2

You could just make your unit test class inherit from Session (assuming your test framework doesn't require that you inherit from a specific class). For instance, with NUnit :

[TestFixture]
public class SessionTest : Session
{
    public SessionTest()
        : base() // call protected constructor
    {
    }

    [Test]
    public void TestSomething()
    {
    }

}

Answer 3

Alternatively, as a workaround, you could just create a TestSession that inherits from Session and exposes a public constructor. Inside your unit-test you then use the TestSession which basically does the same as the original Session object.

public class TestSession : Session
{

   public TestSession() : base()
   {

   }

}