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externalabstractCast

Serenity/JS uses the concept of a cast of actors to centralise the process of configuring the actors and assigning their abilities.

When you invoke actorCalled for the first time in a test scenario, Serenity/JS instantiates a new actor and passes it through the Cast.prepare method. Specifying a custom cast gives you an opportunity to configure the actor with the abilities they need before it's returned to the caller, or configure the actors differently depending on their name. It also helps you to avoid having to configure abilities individually in every test scenario.

Remember

A cast is responsible for assigning abilities to actors in a central location.

Configuring a cast of actors for the entire test suite

When working with relatively simple scenarios where all the actors should always receive the same set of abilities, you can engage Serenity/JS to use a generic Cast.where:

import { Cast, configure } from '@serenity-js/core'
import { CallAnApi } from '@serenity-js/rest'

configure({
  actors: Cast.where(actor => actor.whoCan(
    CallAnApi.at('http://api.example.org'),
    // other abilities
  ))
})

If you're using Serenity/JS with one of the supported test runners, you might prefer to use your test runner's native configuration mechanism instead of invoking engage explicitly.

configure vs engage

Calling configure resets the entire Serenity/JS configuration and should be done exactly once in your entire test suite. If you want to retain the configuration but reset the cast, use engage instead.

Learn more about configuring Serenity/JS with:

Engaging a cast of actors for the specific scenario

If you want to retain Serenity/JS configuration, but set a different cast for the given test scenario you should use engage instead of configure.

This approach is useful for example when your entire test suite is dedicated to interacting with the system under test via its REST APIs, and you have a handful of scenarios that need a web browser.

import { describe, beforeEach } from 'mocha'
import { engage, Cast } from '@serenity-js/core';
import { BrowseTheWebWithPlaywright } from '@serenity-js/playwright'
import { Browser, chromium } from 'playwright'

describe('My UI feature', () => {
  beforeEach(async () => {
    const browser = await chromium.launch({ headless: true })
    engage(Cast.where(actor => actor.whoCan(BrowseTheWebWithPlaywright.using(browser))))
  })

  // test scenarios
})

Writing custom casts for complex scenarios

In complex scenarios that involve multiple actors with different abilities, you should create a custom implementation of the cast.

Examples of such scenarios include those where actors use separate browser instances, interact with different REST APIs, or start with different data in their notepads.

Defining a custom cast of actors interacting with a Web UI

import { beforeEach } from 'mocha'
import { engage, Actor, Cast } from '@serenity-js/core'
import { BrowseTheWebWithPlaywright, PlaywrightOptions } from '@serenity-js/playwright'
import { Browser, chromium } from 'playwright'

export class UIActors implements Cast {
  constructor(
    private readonly browser: Browser,
    private readonly options?: PlaywrightOptions,
  ) {
  }

  prepare(actor: Actor): Actor {
    return actor.whoCan(
      BrowseTheWebWithPlaywright.using(this.browser, this.options),
    )
  }
}

beforeEach(async () => {
  const browser = await chromium.launch({ headless: true })
  engage(new UIActors(browser));
});

Preparing actors differently based on their name

import { beforeEach } from 'mocha'
import { actorCalled, engage, Cast } from '@serenity-js/core'
import { BrowseTheWebWithPlaywright } from '@serenity-js/playwright'
import { CallAnApi } from '@serenity-js/rest'
import { Browser, chromium } from 'playwright'

class Actors implements Cast {
  constructor(
    private readonly browser: Browser,
    private readonly options: PlaywrightOptions,
  ) {
  }

  prepare(actor: Actor) {
    switch (actor.name) {
      case 'James':
        return actor.whoCan(BrowseTheWebWithPlaywright.using(this.browser, this.options));
      default:
        return actor.whoCan(CallAnApi.at(this.options.baseURL));
    }
  }
}

beforeEach(async () => {
  const browser = await chromium.launch({ headless: true })
  engage(new Actors(browser, { baseURL: 'https://example.org' }));
});

actorCalled('James') // returns an actor using a browser
actorCalled('Alice') // returns an actor interacting with an API

Index

Constructors

Methods

Constructors

externalconstructor

Methods

staticexternalwhere

  • Creates a generic Cast implementation, where new actors receive the abilities configured by the prepareFunction.

    Parameters

    Returns Cast

externalabstractprepare

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