test: don't use --runInBand and improve execution performance

[hiroppy]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

modify only

Motivation / Use-Case

Currently, the test's execution performance is too slow because we select serial execution.

Project: https://github.com/webpack/webpack-dev-server/projects/1#card-22555681

In this pr, we can use parallel execution.

Result

serial execution

Test Suites: 1 skipped, 49 passed, 49 of 50 total
Tests:       9 skipped, 419 passed, 428 total
Snapshots:   152 passed, 152 total
Time:        113.313s, estimated 173s
Ran all test suites.

parallel execution

Test Suites: 1 skipped, 49 passed, 49 of 50 total
Tests:       9 skipped, 419 passed, 428 total
Snapshots:   152 passed, 152 total
Time:        60.5s
Ran all test suites.

Strategy

Set the number of ports of each test

see https://github.com/webpack/webpack-dev-server/blob/feature/modify-jest/test/ports-map.js

The key is a file name and the value is the number of ports. We make it easy to change the number of ports flexibly.

globalSetup

see https://github.com/webpack/webpack-dev-server/blob/feature/modify-jest/globalSetupTest.js

We'll use many ports for parallel execution, so we have to make sure that all ports used at boot time are free.

Tests

const [port1, port2] = require('../ports-map')['file-name'];

Breaking Changes

no

Additional Info

NOTE: this pr targets #1996, not next

[codecov]

Codecov Report

Merging #2005 into feature/refactor-tests will not change coverage.
The diff coverage is n/a.

@@                  Coverage Diff                   @@
##           feature/refactor-tests   #2005   +/-   ##
======================================================
  Coverage                    92.4%   92.4%           
======================================================
  Files                          28      28           
  Lines                        1067    1067           
  Branches                      324     324           
======================================================
  Hits                          986     986           
  Misses                         77      77           
  Partials                        4       4

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[alexander-akait]

Good job! Let's merge this in master, we will support webpack-dev-server@3 some time after release 4 version so to avoid problem with merge and releases better refactor tests in master

[hiroppy]

@evilebottnawi I want to merge this to next branch. And I'll create a backport pr to master branch because this change has many conflicts between next and master. anyway, I cannot avoid resolving conflicts.

[alexander-akait]

@hiroppy 👍

[alexander-akait]

Feel free to merge when CI green