I am working with whats going to turn into quite a big node.js-based javascript application and started to think about how I should organize my testing.
The application is basically a REST API, so requests are authenticated, user submitted data is validated and then persisted in a database.
I am completely unfamiliar on how to organize the testing of a project of this size.
Should I test each resource separately starting with modular unit testing, ending with full scale integration testing?
Or should I test layerwise – ie authentication, validation, persistence & integration separately for each resource?
What is common sense?
There is no right or wrong way of testing. Important thing is to have meaningful tests that add value. Its better to have some tests than not having anything.
My approach is to write tests for stuff that I am working on without differentiating unit and integration tests. So, if am working on the REST service then I will write tests for the REST service. If I am working on authentication, persistence then I will write tests for authentication, persistence.
Its also important to write tests that also setup and manage test data needed for the tests. This is important so that anyone can execute your tests. It is also important that your tests can execute on on a Continuous Integration environment out of the box.
Tests for every defect you fix
If am working on a defect, then I will write tests that fails i.e. reproduces the defect and then I verify that my test passes after my code fix. This in my opinion is most important thing to do. As theses tests verify that issues once fixed stay fixed.
Refactoring Code
Value of all the tests you write becomes clear handy when you do some code refactoring. If your refactored code fails your existing tests then your refactored code is broken and needs to be fixed till your all existing tests pass.
When you don’t have time
If you have to pick and choose between the type of tests due to lack of time then or some other reason then writing broader tests or end to end tests or integration tests give the most value as theses tests exercise authentication, persistence, etc directly or indirectly. Compare this to unit tests for persistence you get more out of integration tests as integration tests will tests your persistence indirectly.