Testing Timer-based Logic in Elixir with Klotho Library

Testing code that deals with time, timeouts, and timers can be challenging. Traditional approaches, such as using custom reduced timeouts or :timer.sleep/1, have drawbacks and can lead to slow and flaky tests.

Klotho is a library that provides a different approach to testing timer-based logic in Elixir. It injects timer-based functions globally, allowing developers to control the flow of time in their tests. By using Klotho functions instead of directly calling time-related functions, developers can write tests that are faster, more reliable, and easier to read.

For example, when testing a module that implements a timeout map, Klotho can be used to replace :erlang.cancel_timer/1 and :erlang.start_timer/3 with Klotho.cancel_timer/1 and Klotho.start_timer/3. This allows developers to use arbitrary timeouts in tests without relying on sleeps, resulting in faster and more stable tests.

While Klotho is not suitable for all cases and does not provide beam-wide time injection, it is designed to be used in a wide but limited scope of cases where the code deals with medium-intensive self-contained time-related logic.

By leveraging Klotho, developers can simplify the testing of timer-based logic in Elixir and improve the overall quality of their code.