FIX: Correct unit tests when running WP 5.7

[nielslange]

Fixes #458

Changes

Correct two unit tests that are causing an error when running under WP 5.7.

Steps to test

1. Check out this PR
2. Run phpunit in the plugin directory

Notes

Testing this PR requires a temporary WordPress installation. A temporary WordPress installation can be created with the following steps:

1. Install MariaDB via brew install mariadb
2. Start MariaDB as service via brew services start mariadb
3. Go to plugin directory
4. Run ./bin/install-wp-tests.sh co_authors_plus root root

Please note that this PR only resolves the problem that appears when using WordPress 5.7, the latest available version. It does not resolve the theme-related failed test case when using WordPress 5.3.

Please also note that the previous featured image was an artificial file and not a real image file. This caused a problem in the Twenty Twenty-One theme as this artificial file does not have any metadata such as a height or a width. Therefore, I've replaced that artificial file with a real image dummy file.

[htdat]

Great job here!

If possible, it would be helpful if there was an explanation why this PR changes the way of creating attachments.

As I understand, the old way of creating attachments without a real file will not create metadata for this attachment. And then the test (with WP 5.7) failed in line 136 of TwentyOne theme https://github.com/WordPress/WordPress/blob/5.7/wp-content/themes/twentytwentyone/inc/template-functions.php#L435-L436 as $meta here will be false:

		$meta = wp_get_attachment_metadata( $attachment->ID );
		if ( $meta['width'] && $meta['height'] ) {

[htdat]

Also, it would be nice to create a separate PR to add PHP 7.3 and PHP 7.4 to .travis.yml as currently the plugin is not running tests for these PHP versions.

Co-Authors-Plus/.travis.yml

Lines 22 to 34 in 371d757

	# aliased to a recent 7.x version
	- php: '7.0'
	env: WP_VERSION=5.6.1
	- php: '7.0'
	env: WP_VERSION=latest
	- php: '7.1'
	env: WP_VERSION=5.6.1
	- php: '7.1'
	env: WP_VERSION=latest

[GaryJones]

Could also add TravisCI jobs for PHP 8.0 and nightly (allow_failure) as well

[nielslange]

Also, it would be nice to create a separate PR to add PHP 7.3 and PHP 7.4 to .travis.yml as currently the plugin is not running tests for these PHP versions.

Could also add TravisCI jobs for PHP 8.0 and nightly (allow_failure) as well

@htdat & @GaryJones I created #777 to switch from Travis CI to Circle CI.

[nielslange]

@rebeccahum and @GaryJones Can I have your thoughts regarding the failed Travis CI tests as seen on https://travis-ci.org/github/Automattic/Co-Authors-Plus/builds/766742529? Earlier today, I replaced assertContains() with assertStringContainsString(), as assertContains() is depricated and will be removed with PHPUnit 9. However, this repo was still using PHPUnit 5, which does not support assertStringContainsString() yet. I bumped the PHPUnit version from 5 to 7, to notice that PHPUnit 7 requires PHP 7.1, while the minimum required version to run WordPress is PHP 5.6.

Given that PHP 7.4 or greater is the official recommended version based on https://wordpress.org/about/requirements/, I tend run the PHPUnit tests only against PHP 7.1 or greater. I'm keen to hear your thoughts on this matter.

[GaryJones]

If the plugin is still meant to run on PHP 5.6, then you can use PHPUnit 7.5, and ignore the platform requirements when installing Composer dependencies in the Travis config.

See https://github.com/Yoast/wordpress-seo/blob/ba38278c1d94c09d11f92ed6646930c72e3e4810/.travis.yml#L136-L154 as an example.

[nielslange]

Thanks for your thoughts and pointing out Yoast's example, @GaryJones.

[nielslange]

@rebeccahum Could you look up this change, to check if it's in a shape to get merged, to reduce the noise in the unit tests?