Support delay modes (ctx.delay)

[kettanaito]

Motivation

Using ctx.delay(Infinity) executes the response timer immediately instead of delaying the response indefinitely, as expected. That's due to how setTimeout (that powers response callback to the worker) operates in JavaScript. These changes aim to add support for infinite response delays and add some safeguards against using large integers as the ctx.delay inpt.

Changes

• ctx.delay now supports delay modes—enums that abstract specific delay behaviors:
  • real, uses a random realistic server response time.
  • infinite, uses a maximum allowed integer as a setTimeout duration to delay a response indefinitely (useful when emulating pending/loading states).
• ctx.delay now throws an exception when given Infinity, Number.MAX_VALUE, Number.MAX_SAFE_INTEGER, or any integer value larger than the maximum allowed setTimeout duration.
• ctx.delay now throws an exception when given an unknown delay mode.

Usage

ctx.delay() // realistic response time
ctx.delay(500) // explicit response time
ctx.delay('real') // the same as `ctx.delay()`
ctx.delay('infinite') // infinite response time

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 45a2e13:

Sandbox	Source
MSW React	Configuration

[kettanaito]

Failing to test an infinite delay scenario in Puppeteer, because it throws an exception Target is closed when attempting to close a browser with a pending network request.

[kettanaito]

I've added only the "real" integration test, others seem to be too brittle.

[kettanaito]

Experienced a failing test. Passes locally.

 FAIL  msw-api/setup-server/scenarios/fall-through.node.test.ts (60.105 s)
  ● falls through all relevant handler even if none returns response

    : Timeout - Async callback was not invoked within the 60000 ms timeout specified by jest.setTimeout.Timeout - Async callback was not invoked within the 60000 ms timeout specified by jest.setTimeout.Error:

      41 | })
      42 | 
    > 43 | test('falls through all relevant handler even if none returns response', async () => {
         | ^
      44 |   const res = await fetch('https://test.mswjs.io/blog/article', {
      45 |     method: 'POST',
      46 |   })

      at new Spec (../node_modules/jest-jasmine2/build/jasmine/Spec.js:116:22)
      at Object.<anonymous> (msw-api/setup-server/scenarios/fall-through.node.test.ts:43:1)