Switch

 import { Target } from '@serenity-js/protractor';
 import { by } from 'protractor';

 class LoginForm {
     static iframe           = Target.the('login form').located(by.tagName('iframe'));
     static usernameField    = Target.the('username field').located(by.css('[data-test="username"]'));
     static passwordField    = Target.the('password field').located(by.css('[data-test="password"]'));
     static submitButton     = Target.the('submit button').located(by.css(`button[type='submit']`));
 }

 import { actorCalled } from '@serenity-js/core';
 import { BrowseTheWeb, Switch, Enter, Click } from '@serenity-js/protractor';
 import { protractor } from 'protractor';

 actorCalled('Francesca')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Switch.toFrame(LoginForm.iframe),

         Enter.theValue('francesca@example.org').into(LoginForm.usernameField),
         Enter.theValue('correct-horse-battery-staple').into(LoginForm.passwordField),
         Click.on(LoginForm.submitButton),

         Switch.toParentFrame(),
     );

 import { actorCalled } from '@serenity-js/core';
 import { BrowseTheWeb, Switch, Enter, Click } from '@serenity-js/protractor';
 import { protractor } from 'protractor';

 actorCalled('Francesca')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Switch.toFrame(LoginForm.iframe).and(
             Enter.theValue('francesca@example.org').into(LoginForm.usernameField),
             Enter.theValue('correct-horse-battery-staple').into(LoginForm.passwordField),
             Click.on(LoginForm.submitButton),
         ),
         // Note that Switch.toParentFrame() is invoked automatically
     );

 import { actorCalled } from '@serenity-js/core';
 import { BrowseTheWeb, Switch, Close } from '@serenity-js/protractor';
 import { protractor } from 'protractor';

 actorCalled('Francesca')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Switch.toNewWindow(), // or: Switch.toWindow(...)

         // perform some activities in the context of the new window

         Close.currentWindow(),

         Switch.toOriginalWindow(),
     );

 import { actorCalled } from '@serenity-js/core';
 import { BrowseTheWeb, Switch, Close } from '@serenity-js/protractor';
 import { protractor } from 'protractor';

 actorCalled('Francesca')
     .whoCan(BrowseTheWeb.using(protractor.browser))
     .attemptsTo(
         Switch.toNewWindow().and(
             // perform some activities in the context of the new window

             Close.currentWindow()
         ),

         // Note that Switch.toOriginalWindow() is invoked automatically
     );