Assert call order

This guide adds expect.order to your tests with the @repobuddy/vitest/setup/order setup file.

Steps

1. Add the setup file to test.setupFiles in each config that needs it:

   import { defineConfig } from 'vitest/config'
   import { nodeTestPreset } from '@repobuddy/vitest/config/node'
   
   export default defineConfig({
     plugins: [nodeTestPreset()],
     test: { setupFiles: ['@repobuddy/vitest/setup/order'] },
   })

2. In a test, plan the number of steps with expect.order.plan(n).

3. Call o.once(step) at each step, numbering from 1.

4. Call o.end() after the code under test finishes. It throws InvalidOrder if a planned step was not reached.

expect.order is typed once the setup file is in the config. You do not import anything in the test.

Finished test

it('calls the callbacks in order', () => {
  const o = expect.order.plan(2)

  subject.on('start', () => o.once(1))
  subject.on('end', () => o.once(2))

  subject.run()

  o.end()
})

Verify

1. Run the test. It passes when start fires before end.
2. Swap the two step numbers and run it again. once() throws InvalidOrder.

Related

• @repobuddy/vitest/setup/order
• @repobuddy/test: use installOrder() with another test runner