Add end-to-end tests for edit posts page

[talldanwp]

It'd be great to explore adding more e2e tests for WordPress, and the edit posts/all posts page seems like a good place to start.

I've written a few of these in Gutenberg and I'd like to work on adding some for core.

## Description

Fixes https://core.trac.wordpress.org/ticket/49507

Adds e2e tests for the edit posts page. This is currently a work in progress and not quite ready for review.

Sequel to #200, fixes element targeting issues in some of the tests.

Trac ticket: https://core.trac.wordpress.org/ticket/49507

Should this be closed in favour of ​https://github.com/WordPress/wordpress-develop/pull/1089? Thinking 1089 is ready to go in, all tests green :)

Yep!

I've run the tests, and they work as expected.

@tellthemachines I was wondering, does it make sense to add a README to the e2e folder with information about how to run the test, how to enable headless mode for the tests for instance?

Also, what does this needs to get merged?

Trac ticket: https://core.trac.wordpress.org/ticket/49507

There's a README over here @JustinyAhin - ​https://github.com/WordPress/wordpress-develop/pull/1451.

@tellthemachines @talldan Is this PR ready for commit? Does it overlap any of the work that @JustinyAhin is doing?

@hellofromtonya yup, this one's ready to go. It doesn't overlap with Justin's PRs as this is specific to the posts screen and Justin has been focusing on other screens so far.

[hellofromTonya]

As part of 5.9's e2e roadmap, moving this ticket into 5.9. As the PR is ready to go, marking it for commit and assigning it to me to do the commit.

When running this test locally (via npm run test:e2e), I get the following error:

 FAIL  tests/e2e/specs/edit-posts.test.js (76.359 s)
  ● Edit Posts › allows an existing post to be edited using the Edit button

    TimeoutError: waiting for selector `.components-snackbar` failed: timeout 30000ms exceeded

      44 | 		const title = 'Test Title';
      45 | 		await createNewPost( { title } );
    > 46 | 		await publishPost();
         | 		^
      47 | 		await visitAdminPage( '/edit.php' );
      48 |
      49 | 		await page.waitForSelector( '#the-list .type-post' );

      at new WaitTask (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:780:28)
      at DOMWorld.waitForSelectorInPage (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:632:22)
      at Object.internalHandler.waitFor (../../node_modules/puppeteer-core/src/common/QueryHandler.ts:78:19)
      at DOMWorld.waitForSelector (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:490:25)
      at Frame.waitForSelector (../../node_modules/puppeteer-core/src/common/FrameManager.ts:1163:47)
      at Page.waitForSelector (../../node_modules/puppeteer-core/src/common/Page.ts:2100:29)
      at publishPost (../../node_modules/@wordpress/e2e-test-utils/build/@wordpress/e2e-test-utils/src/publish-post.js:19:14)
          at runMicrotasks (<anonymous>)
      at Object.<anonymous> (specs/edit-posts.test.js:46:3)

  ● Edit Posts › allows an existing post to be deleted using the Trash button

    TimeoutError: waiting for selector `.components-snackbar` failed: timeout 30000ms exceeded

      110 | 		const title = 'Test Title';
      111 | 		await createNewPost( { title } );
    > 112 | 		await publishPost();
          | 		^
      113 | 		await visitAdminPage( '/edit.php' );
      114 |
      115 | 		await page.waitForSelector( '#the-list .type-post' );

      at new WaitTask (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:780:28)
      at DOMWorld.waitForSelectorInPage (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:632:22)
      at Object.internalHandler.waitFor (../../node_modules/puppeteer-core/src/common/QueryHandler.ts:78:19)
      at DOMWorld.waitForSelector (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:490:25)
      at Frame.waitForSelector (../../node_modules/puppeteer-core/src/common/FrameManager.ts:1163:47)
      at Page.waitForSelector (../../node_modules/puppeteer-core/src/common/Page.ts:2100:29)
      at publishPost (../../node_modules/@wordpress/e2e-test-utils/build/@wordpress/e2e-test-utils/src/publish-post.js:19:14)
          at runMicrotasks (<anonymous>)
      at Object.<anonymous> (specs/edit-posts.test.js:112:3)

 PASS  tests/e2e/specs/dashboard.test.js
 PASS  tests/e2e/specs/hello.test.js

Test Suites: 1 failed, 2 passed, 3 total
Tests:       2 failed, 6 passed, 8 total
Snapshots:   0 total
Time:        79.215 s

@tellthemachines Does it pass locally for you?

When running this test locally (via npm run test:e2e), I get the following error:

 FAIL  tests/e2e/specs/edit-posts.test.js (76.359 s)
  ● Edit Posts › allows an existing post to be edited using the Edit button

    TimeoutError: waiting for selector `.components-snackbar` failed: timeout 30000ms exceeded

      44 | 		const title = 'Test Title';
      45 | 		await createNewPost( { title } );
    > 46 | 		await publishPost();
         | 		^
      47 | 		await visitAdminPage( '/edit.php' );
      48 |
      49 | 		await page.waitForSelector( '#the-list .type-post' );

      at new WaitTask (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:780:28)
      at DOMWorld.waitForSelectorInPage (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:632:22)
      at Object.internalHandler.waitFor (../../node_modules/puppeteer-core/src/common/QueryHandler.ts:78:19)
      at DOMWorld.waitForSelector (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:490:25)
      at Frame.waitForSelector (../../node_modules/puppeteer-core/src/common/FrameManager.ts:1163:47)
      at Page.waitForSelector (../../node_modules/puppeteer-core/src/common/Page.ts:2100:29)
      at publishPost (../../node_modules/@wordpress/e2e-test-utils/build/@wordpress/e2e-test-utils/src/publish-post.js:19:14)
          at runMicrotasks (<anonymous>)
      at Object.<anonymous> (specs/edit-posts.test.js:46:3)

  ● Edit Posts › allows an existing post to be deleted using the Trash button

    TimeoutError: waiting for selector `.components-snackbar` failed: timeout 30000ms exceeded

      110 | 		const title = 'Test Title';
      111 | 		await createNewPost( { title } );
    > 112 | 		await publishPost();
          | 		^
      113 | 		await visitAdminPage( '/edit.php' );
      114 |
      115 | 		await page.waitForSelector( '#the-list .type-post' );

      at new WaitTask (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:780:28)
      at DOMWorld.waitForSelectorInPage (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:632:22)
      at Object.internalHandler.waitFor (../../node_modules/puppeteer-core/src/common/QueryHandler.ts:78:19)
      at DOMWorld.waitForSelector (../../node_modules/puppeteer-core/src/common/DOMWorld.ts:490:25)
      at Frame.waitForSelector (../../node_modules/puppeteer-core/src/common/FrameManager.ts:1163:47)
      at Page.waitForSelector (../../node_modules/puppeteer-core/src/common/Page.ts:2100:29)
      at publishPost (../../node_modules/@wordpress/e2e-test-utils/build/@wordpress/e2e-test-utils/src/publish-post.js:19:14)
          at runMicrotasks (<anonymous>)
      at Object.<anonymous> (specs/edit-posts.test.js:112:3)

 PASS  tests/e2e/specs/dashboard.test.js
 PASS  tests/e2e/specs/hello.test.js

Test Suites: 1 failed, 2 passed, 3 total
Tests:       2 failed, 6 passed, 8 total
Snapshots:   0 total
Time:        79.215 s

@tellthemachines Does it pass locally for you?

@hellofromtonya it passes for me! I rebased the branch in case it helps at all.

[hellofromTonya]

In 51990:

Build/Test Tools: Add end-to-end (e2e) tests for edit posts page.

Adds e2e tests for 'Edit Posts':

• No posts found
• Shows a single post after publishing
• Edit existing post via Edit button
• Quick edit existing post via Quick Edit button
• Delete post

Props isabel_brison, azaozz, hellofromTonya, justinahinon, talldanwp, youknowriad.
Fixes #49507.

Committed via changeset https://core.trac.wordpress.org/changeset/51990.