Angular: Handling Time and Mock Clocks in Tests

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In the realm of software testing, the concept of time can be a tricky one to manage, especially when dealing with asynchronous operations and timeouts. We are continually refining our approach to handling time in unit tests, particularly concerning the use of mock clocks. We’ve found that mock clocks, while useful, often lead to headaches in test code and unrealistic timing scenarios. To address these challenges, we are exploring the exciting concept of “auto-advancing” mock clocks, which aim to streamline testing and enhance the accuracy of time-based simulations. In this blog post, we’ll delve into the intricacies of mock clocks, their limitations, and the potential benefits of auto-advancing functionality.

Why use a mock clock

We see a few reasons to install mock clocks in tests.

1. To fake the date. This makes it possible to test components which display the current time or date related information, or do some calculation with respect to the current time.
2. More frequently, to speed up time. UIs are frequently written with debounces, visible delays for users, timeouts, etc. We want to verify the state of the app after these long-running tasks complete but we don’t want the test to actually wait 30 seconds for a timeout. Instead, mock clocks can fake the progression of time without needing to modify the production code to expose some overridable timeout simply to make the test quicker.
3. To prevent timers from leaking into other tests, creating action at a distance errors. Mock clocks can uninstall after each test and either dispose of or flush any pending timers.
4. To execute all pending timers or stabilize the test. This...

Get the full details here: https://blog.angular.dev/handling-time-and-mock-clocks-in-tests-5a393b32dd30?source=rss----447683c3d9a3---4