Symmetrical Unit Test - testdouble/contributing-tests GitHub Wiki

A unit test is said to be "symmetrical" with its subject when:

• It's placed in a directory that mirrors the subject and with a name that can be predicted by its filename (e.g. lib/foo.js is tested by lib/foo-test.js)
• It is the only unit test of the public behavior of the subject
• It does not effectively specify the behavior of the subject's dependencies