describe('a test suite', () => {
  it('should pass', () => {
    expect(true).toBeTrue();
  });
  it('should fail', () => {
    expect(true).toBeFalse();
  });

  describe('an inner test suite', () => {
    it("should pass 2", () => {
      expect(undefined).toBeUndefined();
    });
    it("should fail 2", () => {
      expect(undefined).toBeTrue();
    });

    describe('another inner test suite', () => {
      it("should pass 3", () => {
        expect(null).toBeNull();
      });
      it("should fail 3", () => {
        expect(null).toBeTrue();
      });
    });
  });
});