unique-constraints.md

Fighting with Unique Constraints

Preconditions:

• Our Person has unique username - 2 people cannot register with the same username.
• Our test is run against a remote instance of the app and Persons persist between 2 test runs

The 1st time we run the test everything is great:

@Test public void canRegisterNewUser() {
        String username = "feynman";
        RestService.instance.save(new Person(username));
    }

The 2nd time we run it - it fails because user feynman already exists in DB. What do we do?

Option 1: Clear DB between test runs

• Write an external shell script that logs in to the DB and clears it. Ouch! This appears to be more complicated than it looks.
• The script needs to be run both from CI Server as well as on local machines of devs/testers.
• Won't save when multiple people are running tests at the same time against the same env

Option 2: Clear tests data before test run

• Again - complicated since for each unique piece of data we need a way to clean it.
• Need to write logic to access DB? If DB is refactored the tests would fail.
• Need to write backdoors in the API? Still additional efforts. And need to keep that API from production some how.
• Still won't save when multiple people are running tests against the same env

Option 3: Randomization

@Test public void canRegisterNewUser() {
    String username = alphanumeric(1, 20);
    RestService.instance.save(new Person(username));
}