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Test and Mock Asynchronous Calls With the Jest Testing Framework
A detailed guide on how to set up unit test cases for asynchronous calls
Unit testing isolates each part of the program and verifies that the individual parts are correct. Unit test cases are typically automated tests written and run by developers. This enables problems to be discovered early in the development cycle. Jest is a JavaScript testing framework to ensure the correctness of any JavaScript codebase.
Asynchronous calls don’t block or wait for calls to return. After the call is made, program execution continues. When the call returns, a callback function is executed. It’s hard to test asynchronous calls due to the asynchronous nature.
The Pitfall of Asynchronous Calls
The following is a unit test case for an asynchronous call, setTimeout.
Apparently, 1 isn’t 2, but the test passes.
This is the pitfall of asynchronous calls. Line 3 calls setTimeout and returns. The test…
