Unit testing vs Integration testing

[w2vgd]

Hi, I realized that in the original AB3 code, when testing the Person class in PersonTest, the code uses PersonBuilder which in turn uses all of the attribute classes such as Name and Phone to build the Person object. So in this case, is PersonTest a form of integration testing? If it is, why is it tested using integration testing instead of unit testing in this case?

Another follow up question is when do we know if a class should be tested using unit testing (isolated from other class and only uses stubs if necessary) or integration testing?

[damithc]

While keeping the door open for others' comments about this specific situation, here are some general thoughts:

When writing test cases for something, decisions to make include:

• Should it be unit/integration tested at all? Rely on higher-level tests instead? Rely on manual tests instead?
• Should we use pure unit testing, pure integration testing, a hybrid approach, ...?

Factors to consider include:

• The benefits: depends on things like how complicated the code is, how complicated the way it interacts with other parts, how easy is it to break, will it be obvious if there is a bug or will it go unnoticed, how much damage can a bug in this code cause, ...
• The costs: how easy is it to isolate the unit, how often the tests will need to be updated as the code evolves, how much time it will add to a CI run, ...

As usual, it requires a judgement call for each specific situation. If the code has dependencies, it is more common to use a hybrid approach rather than pure unit and integration testing.

[ong6]

Regarding the second part of your question, I think it is heavily dependent on what you're comfortable with. If you feel like there may be changes to some essential part of the code down the line, unit testing is definitely a better choice as it won't be too dependent on other parts of the code working. However, if you feel like you're close to completion, integration testing could be a good sanity check to see if different modules of your product are working.