Adam Wathan: Writing Your Own Test Doubles

In this recent post to his site Adam Wathan about writing your own custom test doubles (fakes) to help make your tests cleaner and improve their overall readability/maintainability.

Once in a while I run into a situation where trying to use a mocking library hurts the readability of my test. For example, say I’m building out a basic user registration flow where someone signs up and receives a welcome email. […] To test that an account is created correctly, I can make a request to the endpoint and verify that the new account exists in a test database. […] This covers creating the account itself, but what’s the best way to test the welcome email?

He goes through a few of the options that could be used to test this including using Mockery to replace the mailer class with a spy or actually sending emails. There’s downfalls to both of these methods and he suggests using a custom "fake" where the mailer class is swapped out with an "in-memory" option with the same kind of interface. He does point out a few issues with this method, however, and offers a few tips to remember when using them.

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