How to use the power-assert function in power-assert

it('click()', function() {
    let spy = sinon.spy(function(e) {
      // noop
    });

    let target = document.createElement('div');
    click(target).subscribe(spy);

    ClickEvent.simulate(target);
    assert(spy.calledOnce);
    ClickEvent.simulate(target);
    assert(spy.calledTwice);
    ClickEvent.simulate(target);
    assert(spy.calledThrice);
  });

it('should support keyCode up & down', () => {
        const dataSource = [
            { label: 'xxx', value: 'a' },
            { label: 'empty', value: 'b' },
        ];
        wrapper.setProps({
            dataSource,
            visible: true,
        });
        wrapper.find('input').simulate('keydown', { keyCode: 40 });
        wrapper.find('input').simulate('keydown', { keyCode: 40 });
        wrapper.update();
        assert(
            document.querySelectorAll('.next-menu-item.next-focused').length ===
                1
        );
        wrapper.find('input').simulate('keydown', { keyCode: 13 });
        wrapper.update();
        assert(wrapper.find('input').prop('value') === 'b');

        wrapper.find('input').simulate('keydown', { keyCode: 38 });
        wrapper.find('input').simulate('keydown', { keyCode: 27 });
        wrapper.find('input').simulate('keydown', { keyCode: 32 });
        wrapper.find('input').simulate('keydown', { keyCode: 8 });
        wrapper.find('input').simulate('keydown', { keyCode: 9 });

        // wrapper.find('input').simulate('keydown', {keyCode: 38});
        // wrapper.find('input').simulate('keydown', {keyCode: 13});
        // assert(wrapper.find('input').prop('value') === 'a');

it('should support once method', function() {
        let flag = false;
        events.once(element, 'click', function(e) {
            flag = true;
            assert(e.target === element);
        });

        simulateEvents.simulate(element, 'click');
        assert(flag);
        flag = false;
        simulateEvents.simulate(element, 'click');
        assert(!flag);
    });
});

it("defines a callback property", () => {
    class Foo {
      constructor() {
        this._ = {};
      }

      @props.on("end")
      onend() {}
    }

    const foo = new Foo();

    assert(foo.onend === null);
    assert.doesNotThrow(() => { foo.onend = it; });
    assert(foo.onend === it);
    assert.throws(() => { foo.onend = "not a function"; }, TypeError);
  });
});

it('should test if a file exists', () => {
      const validPath = join(__dirname, 'fs.js')
      const invalidPath = join(__dirname, 'path-to-nowhere.js')

      assert(exists(validPath))
      assert(!exists(invalidPath))
    })
  })

it('field1.pristine should be true', () => {
          assert(vm.$validator1.field1.pristine === true)
        })
        it('field2.pristine should be false', () => {

accessToken.delete().then(response => {
    const cookies = response.meta.headers["set-cookie"];
    const parsedCookie = cookie.parse(cookies);
    assert(parsedCookie["access-token"] === "null");
    assert(parsedCookie.Expires === "Thu, 01 Jan 1970 00:00:00 GMT");
  });
});

let store1 = new Store();
    let store2 = new Store();
    let spy1 = sinon.spy();
    let spy2 = sinon.spy();

    domain.addStore(store1);
    domain.addStore(store2);
    store1.storeReceiveDispatch = spy1;
    store2.storeReceiveDispatch = spy2;

    domain.dispatch(DISPATCH_TEST1, arg);
    assert(spy1.withArgs(DISPATCH_TEST1, arg).calledOnce);
    assert(spy2.withArgs(DISPATCH_TEST1, arg).calledOnce);

    domain.dispatch(DISPATCH_TEST2, arg);
    assert(spy1.withArgs(DISPATCH_TEST2, arg).calledOnce);
    assert(spy2.withArgs(DISPATCH_TEST2, arg).calledOnce);
  });

it('should add and remove transparent selection class', function () {
         drag = TestUtils.renderIntoDocument(
           
             <div>
           
         );

         const node = ReactDOM.findDOMNode(drag);

         assert(!document.body.classList.contains('react-draggable-transparent-selection'));
         TestUtils.Simulate.mouseDown(node, {clientX: 0, clientY: 0});
         assert(document.body.classList.contains('react-draggable-transparent-selection'));
         TestUtils.Simulate.mouseUp(node);
         assert(!document.body.classList.contains('react-draggable-transparent-selection'));
       });
</div>

return Harness.testCreate(EditGridComponent, comp1).then((component) => {
      Harness.testSetGet(component, [
        {
          field1: 'good',
          field2: 'foo'
        },
        {
          field1: 'good',
          field2: 'bar'
        }
      ]);
      Harness.clickElement(component, 'li.list-group-item:nth-child(3) div.editRow');
      assert(!component.checkValidity(component.getValue(), true), 'Item should not be valid');
      Harness.clickElement(component, 'div.editgrid-actions button.btn-primary');
      assert(component.checkValidity(component.getValue(), true), 'Item should be valid');
      Harness.clickElement(component, 'li.list-group-item:nth-child(3) div.editRow');
      assert(!component.checkValidity(component.getValue(), true), 'Item should not be valid');
      Harness.clickElement(component, 'div.editgrid-actions button.btn-danger');
      assert(component.checkValidity(component.getValue(), true), 'Item should be valid');
    });
  });