@serenity-js/assertions
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Serenity/JS universal assertion library supporting all types of functional tests, including both web and REST API scenarios
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# Serenity/JS
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[Serenity/JS](https://serenity-js.org) is an innovative open-source framework designed to make acceptance and regression testing
of complex software systems faster, more collaborative and easier to scale.
āļø Get started with Serenity/JS!
- [Serenity/JS web testing tutorial](https://serenity-js.org/handbook/web-testing/your-first-web-scenario)
- [Serenity/JS Handbook](https://serenity-js.org/handbook)
- [API documentation](https://serenity-js.org/api/)
- [Serenity/JS Project Templates](https://serenity-js.org/handbook/project-templates/)
š Join the Serenity/JS Community!
- Meet other Serenity/JS developers and maintainers on the [Serenity/JS Community chat channel](https://matrix.to/#/#serenity-js:gitter.im),
- Find answers to your Serenity/JS questions on the [Serenity/JS Forum](https://github.com/orgs/serenity-js/discussions/categories/how-do-i),
- Learn how to [contribute to Serenity/JS](https://serenity-js.org/community/contributing/),
- Support the project and gain access to [Serenity/JS Playbooks](https://github.com/serenity-js/playbooks) by becoming a [Serenity/JS GitHub Sponsor](https://github.com/sponsors/serenity-js)!
## Serenity/JS Assertions
[`@serenity-js/assertions`](https://serenity-js.org/api/rest/) is an assertions library implementing the [Screenplay Pattern](https://serenity-js.org/handbook/design/screenplay-pattern/).
### Installation
To install this module, run the following command in your computer terminal:
```sh
npm install --save-dev @serenity-js/core @serenity-js/assertions
```
### Performing verifications using `Ensure`
```typescript
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`
```typescript
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`
```typescript
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`
```typescript
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`
```typescript
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)),
)
```
## š£ Stay up to date
New features, tutorials, and demos are coming soon!
Follow [Serenity/JS on LinkedIn](https://www.linkedin.com/company/serenity-js),
subscribe to [Serenity/JS channel on YouTube](https://www.youtube.com/@serenity-js) and join the [Serenity/JS Community Chat](https://matrix.to/#/#serenity-js:gitter.im) to stay up to date!
Please also make sure to star āļø [Serenity/JS on GitHub](https://github.com/serenity-js/serenity-js) to help others discover the framework!
[](https://www.linkedin.com/company/serenity-js)
[](https://www.youtube.com/@serenity-js)
[](https://matrix.to/#/#serenity-js:gitter.im)
[](https://github.com/serenity-js/serenity-js)
## š Support Serenity/JS
If you appreciate all the effort that goes into making sophisticated tools easy to work with, please support our work and become a Serenity/JS GitHub Sponsor today!
[](https://github.com/sponsors/serenity-js)