Arrange-Act-Assert(AAA) Pattern | Angular unit test case Tutorials with Jasmine & Karma

Arrange-Act-Assert is a great way to structure test cases. It prescribes an order of operations:

Arrange inputs and targets. Arrange steps should set up the test case. Does the test require any objects or special settings? Does it need to prep a database? Does it need to log into a web app? Handle all of these operations at the start of the test.

Act on the target behaviour. Act steps should cover the main thing to be tested. This could be calling a function or method, calling a REST API, or interacting with a web page. Keep actions focused on the target behaviour.

Assert expected outcomes. Act steps should elicit some sort of response. Assert steps verify the goodness or badness of that response. Sometimes, assertions are as simple as checking numeric or string values. Other times, they may require checking multiple facets of a system. Assertions will ultimately determine if the test passes or fails.

You can learn more on it from below video