[angular] How to write unit testing for Angular / TypeScript for private methods with Jasmine

Do not write tests for private methods. This defeats the point of unit tests.

  • You should be testing the public API of your class
  • You should NOT be testing the implimentation details of your class

Example

class SomeClass {

  public addNumber(a: number, b: number) {
      return a + b;
  }
}

The test for this method should not need to change if later the implementation changes but the behaviour of the public API remains the same.

class SomeClass {

  public addNumber(a: number, b: number) {
      return this.add(a, b);
  }

  private add(a: number, b: number) {
       return a + b;
  }
}

Don't make methods and properties public just in order to test them. This usually means that either:

  1. You are trying to test implementation rather than API (public interface).
  2. You should move the logic in question into its own class to make testing easier.

Examples related to angular

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Examples related to typescript

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