First pass at phpunit tests

[dsawardekar]

Requirements

First attempt at unit tests for the PHP code.

Description of the Change

This PR includes tests for,

• Admin Bar & Menus
• Assets manager
• Classic Editor Toggle manager

Alternate Designs

NA

Benefits

Improved maintainability and test coverage.

Possible Drawbacks

NA

Verification Process

vendor/bin/phpunit

Running as single site... To run multisite, use -c tests/phpunit/multisite.xml
Not running ajax tests. To execute these, use --group ajax.
Not running ms-files tests. To execute these, use --group ms-files.
Not running external-http tests. To execute these, use --group external-http.
PHPUnit 7.5.20 by Sebastian Bergmann and contributors.

....................                                              20 / 20 (100%)

Time: 440 ms, Memory: 30.00 MB

OK (20 tests, 27 assertions)

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

NA

Changelog Entry

Added initial PHPUnit Tests.

[tlovett1]

Hey @dsawardekar we changed the plugin name to "Convert to Blocks. Can you refactor the PR please?

[jeffpaul]

Please update to "Convert to Blocks" naming

[dsawardekar]

@tlovett1 @jeffpaul I have refactored the PR to reflect the new name. And also fixed the failing tests and linter warnings.