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Mastering TypeScript

Test Setup and Teardown

Explore how to implement test setup and teardown functions using Jest in TypeScript. Understand how beforeAll, beforeEach, afterEach, and afterAll control test environments and state. Learn to write reliable tests by initializing and cleaning up test conditions automatically before and after your test cases run.

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Before we run a particular test, we may wish to exercise some code beforehand. This may be to initialize a particular variable or to make sure that the dependencies of an object have been set up.

In the same vein, we may wish to execute some code once a particular test has run or even after a full test suite has run. To illustrate this, consider the following class:

TypeScript 4.9.5
class GlobalCounter {
 count: number = 0;
 increment(): void {
   this.count++;
 }
}

Here, we have a class named GlobalCounter that has a count property and an increment function.

The count property is set to 0 when the class is instantiated, and the ...