The title is probably not very clear. I have the following example in mind:
an Authenticator object authenticates a user using credentials. It returns a AuthResult object. This AuthResult object says the authentication succeeded, or that it failed (and if so, why it failed, eg username not found).
How can I phrase this in a test? ‘testShouldReturnAuthObjectWithStatusSuccessOnValidLogin’?
testValidLoginIsSuccessful or testIsSuccessfulOnValidLogin seems good enough for me.
For error tests, you could use something like testGetsCustomMessageOnUserNotFound
You should avoid putting implementation details in the method name.