chai-wait-for

Drop-in replacement for expect that waits for the assertion to succeed (retries on an interval you choose, until a timeout you choose).

Provides an especially clean syntax for working with some chai plugins like chai-fs, chai-webdriverio-async etc:

1await waitFor('#submittedMessage').to.have.text('Your changes have been saved!')

Usage

1npm install --save-dev chai-wait-for

1// First, use the plugin
2const chai = require('chai')
3const chaiWaitFor = require('chai-wait-for')
4const { afterEach } = require('mocha')
5chai.use(chaiWaitFor)
6
7// Then create your `waitFor` with default options:
8const waitFor = chaiWaitFor.bindWaitFor({
9  // If no assertion attempt succeeds before this time elapses (in milliseconds), the waitFor will fail.
10  timeout: 5000,
11  // If an assertion attempt fails, it will retry after this amount of time (in milliseconds)
12  retryInterval: 100,
13  // this is optional, but asserts that you didn't forget to await any waitFor() calls
14  failOnDanglingCalls: afterEach,
15})
16
17it('wait for something', async function () {
18  this.timeout(10000)
19
20  const myObj = { foo: 0 }
21
22  setInterval(() => myObj.foo++, 1000)
23
24  // Then use it just like you would expect() (but note you must await it!)
25  await waitFor(myObj).to.have.property('foo').that.equals(3)
26
27  // You can also use a getter function:
28  await waitFor(() => myObj.foo).to.equal(4)
29
30  // If you need to override the defaults:
31  await waitFor.timeout(1000)(myObj).to.have.property('foo').that.equals(3)
32  await waitFor.retryInterval(500)(myObj).to.have.property('foo').that.equals(3)
33})

Plugin usage order/usage with chai-as-promised

All chai language chains that were defined before you use chai-wait-for will be available to use with it.

This is similar to chai-as-promsied, but although you generally need to chai.use(require('chai-as-promised')) after all your other chai plugins, this is actually not the case for chai-wait-for, because chai-wait-for doesn't add or overwrite any language chains. Instead you should use chai-wait-for after chai-as-promised, so that you can waitFor .eventually assertions:

1const chai = require('chai')
2const chaiWaitFor = require('chai-wait-for')
3chai.use(require('chai-as-promised'))
4chai.use(chaiWaitFor)
5
6const waitFor = chaiWaitFor.bindWaitFor({ retryInterval: 100, timeout: 5000 })
7
8it('wait for something', async function () {
9  // User.findOne returns a promise; use .eventually.not.exist to wait for user to be deleted
10  await waitFor(() => User.findOne({ where: { username: 'dude' } })).to
11    .eventually.not.exist
12})