test: refactor use-swr-refresh.test.tsx

[koba04]

This is a follow-up PR of #933.
I've refactored use-swr-refresh.test.tsx.

The test file is the slowest test in vercel/swr because it has many tests depend on setTimeout/setInterval timers.
Reducing the interval of timers makes tests flaky, so I've used Jest's fake timers to reduce the total test time.

• Before

➜  yarn test                                                                                                                                                                                                                 
yarn run v1.22.10
$ jest
 PASS  test/use-swr-config-callbacks.test.tsx
 PASS  test/use-swr-concurrent-mode.test.tsx
 PASS  test/use-swr-revalidate.test.tsx
 PASS  test/use-swr-key.test.tsx
 PASS  test/use-swr-configs.test.tsx
 PASS  test/use-swr-focus.test.tsx
 PASS  test/use-swr-loading.test.tsx
 PASS  test/use-swr-offline.test.tsx
 PASS  test/use-swr-context-config.test.tsx
 PASS  test/use-swr-infinite.test.tsx
 PASS  test/use-swr-suspense.test.tsx
 PASS  test/use-swr-cache.test.tsx
 PASS  test/use-swr-integration.test.tsx
 PASS  test/use-swr-local-mutation.test.tsx
 PASS  test/use-swr-error.test.tsx
 PASS  test/use-swr-refresh.test.tsx (6.37s)

Test Suites: 16 passed, 16 total
Tests:       110 passed, 110 total
Snapshots:   55 passed, 55 total
Time:        8.228s
Ran all test suites.
✨  Done in 9.83s.

• After

➜  yarn test
yarn run v1.22.10
$ jest
 PASS  test/use-swr-refresh.test.tsx
 PASS  test/use-swr-config-callbacks.test.tsx
 PASS  test/use-swr-concurrent-mode.test.tsx
 PASS  test/use-swr-configs.test.tsx
 PASS  test/use-swr-loading.test.tsx
 PASS  test/use-swr-revalidate.test.tsx
 PASS  test/use-swr-key.test.tsx
 PASS  test/use-swr-context-config.test.tsx
 PASS  test/use-swr-cache.test.tsx
 PASS  test/use-swr-focus.test.tsx
 PASS  test/use-swr-offline.test.tsx
 PASS  test/use-swr-suspense.test.tsx
 PASS  test/use-swr-infinite.test.tsx
 PASS  test/use-swr-integration.test.tsx
 PASS  test/use-swr-error.test.tsx
 PASS  test/use-swr-local-mutation.test.tsx

Test Suites: 16 passed, 16 total
Tests:       110 passed, 110 total
Snapshots:   23 passed, 23 total
Time:        5.803s
Ran all test suites.
✨  Done in 7.29s.

[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 b5077bb:

Sandbox	Source
SWR-Basic	Configuration
SWR-States	Configuration
SWR-Infinite	Configuration
SWR-SSR	Configuration

[shuding]

Thank you! Never used Jest fake timers before but it looks awesome :)

[koba04]

Thank you!