Protractor test in Angular 6 for login screen

I am new in the Protractor testing for Angular 6 application. I am trying to write the spec test for login page as below.

describe('Protractor Login checing ', function() {
    it('should add one and two', function() {
        browser.get('http://localhost:4041/login');
        element(by.model('username')).sendKeys('admin');
        element(by.model('password')).sendKeys('admin');

        element(by.id('login')).click();

        // Here, What should I check whether authentication has been done or not..
        // expect().toEqual('');
    });
});

Actually, In My application, once logic is a success, then I will show a success message in snackBar (Angular material) and redirect into dashboard page.

// Angular 6 application    
this.snackBar.open(res.message, '', {
                duration: 6000,
              });

Here, how should I check in protractor? Anyone help me to do this?

You should check the url has changed or not -

describe('Protractor Login checing ', function() {
    it('should add one and two', function() {
    browser.get('http://localhost:4041/login');
    element(by.model('username')).sendKeys('admin');
    element(by.model('password')).sendKeys('admin');

    element(by.id('login')).click();

    browser.wait(waitForUrlChange("http://localhost:4041/dashboard"), 8000, function(){
      browser.getCurrentUrl().then(function (currentUrl) {
          expect(currentUrl.toEqual("http://localhost:4041/dashboard"));
      });
  }));
 });

function waitForUrlChange(url) {
    return function () {
        return browser.getCurrentUrl().then(function (currentUrl) {
            console.log(currentUrl);
            return url === currentUrl;
        });
    }
}