How to unit test a void method

Question

I am trying to reach more code coverage. I have an "informational" method that just triggers notification, and response is not required. How do I unit test it?

public error(message?: any, ...optionalParams: any[]) {
    if (this.isErrorEnabled()) {
      console.error(`${this.name}: ${message}`, ...optionalParams);
    }
  }

Solution

You can test its side effects using spies, for example:

describe('error method', => {
    it('should log an error on the console', () => {
        spyOn(console, 'error');

        error(...);

        expect(console.error).toHaveBeenCalledWith(...);
    });

    ...
});