Snapshot testing #

Earl supports snapshots tests. They are different from Jest's in that they don't rely on hooking into the test runner, but require you to pass this to toMatchSnapshot. Currently snapshots testing is only supported in Mocha.

Inline snapshots are not supported.

Basic usage #

import { expect } from 'earljs'

describe('snapshots', () => {
  // Note the `function () {` instead of `() => {`
  // This is because we need to pass `this` to `toMatchSnapshot`
  it('works', function () {
    expect({ very: { nested: { wow: 'wow' } } }).toMatchSnapshot(this)
  })
})

Matches actual value to a snapshot. The name of the snapshot is derived from the suite and test case names. A snapshot file will be named (filename).snapshot - e.g. for candy.test.ts it will be candy.test.ts.snapshot.

If a snapshot doesn't exist, it will be created. If it exists, actual values will be asserted against it. Set UPDATE_SNAPSHOTS=true environment variable to update snapshots instead. On CI no snapshots will be updated/created.

Multiple snapshots in one test case work as expected.

Read more #

• Effective snapshot testing (MUST READ)