@serenity-js/assertions

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Serenity/JS Assertions

@serenity-js/assertions is an assertions library implementing the Screenplay Pattern.

Installation

To install this module, run the following command in your computer terminal:

npm install --save-dev @serenity-js/core @serenity-js/assertions

To learn more about Serenity/JS and how to use it on your project, follow the Serenity/JS Getting Started guide.

Performing verifications using Ensure

import { Ensure, endsWith } from '@serenity-js/assertions'
import { actorCalled } from '@serenity-js/core'
import { Navigate, Page } from '@serenity-js/web'

await actorCalled('Erica').attemptsTo(
    Navigate.to('https://serenity-js.org'),
    Ensure.that(
        Page.current().title(), 
        endsWith('Serenity/JS')
    ),
)

Controlling execution flow using Check

import { actorCalled } from '@serenity-js/core'
import { Check } from '@serenity-js/assertions' 
import { Click, isVisible } from '@serenity-js/protractor'

await actorCalled('Erica').attemptsTo(
    Check.whether(NewsletterModal, isVisible())
        .andIfSo(Click.on(CloseModalButton)),
)

Synchronising the test with the System Under Test using Wait

import { actorCalled } from '@serenity-js/core'
import { Click, isVisible, Wait } from '@serenity-js/protractor'

await actorCalled('Erica').attemptsTo(
    Wait.until(CloseModalButton, isVisible()),
    Click.on(CloseModalButton)
)

Defining custom expectations using Expectation.thatActualShould

import { actorCalled } from '@serenity-js/core'
import { Expectation, Ensure } from '@serenity-js/assertions'

function isDivisibleBy(expected: Answerable<number>): Expectation<number> {
    return Expectation.thatActualShould<number, number>('have value divisible by', expected)
        .soThat((actualValue, expectedValue) => actualValue % expectedValue === 0)
}

await actorCalled('Erica').attemptsTo(
    Ensure.that(4, isDivisibleBy(2)),
)

Composing expectations using Expectation.to

import { actorCalled } from '@serenity-js/core'
import { Expectation, Ensure, and, or, isGreaterThan, isLessThan, equals  } from '@serenity-js/assertions'

function isWithin(lowerBound: number, upperBound: number) {
    return Expectation
        .to(`have value within ${ lowerBound } and ${ upperBound }`)
        .soThatActual(and(
           or(isGreaterThan(lowerBound), equals(lowerBound)),
           or(isLessThan(upperBound), equals(upperBound)),
        ))
}

await actorCalled('Erica').attemptsTo(
    Ensure.that(5, isWithin(3, 6)),
)

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