Tests: Use `assertSame()` in some newly introduced tests.

This ensures that not only the return values match the expected results, but also that their type is the same.

Going forward, stricter type checking by using `assertSame()` should generally be preferred to `assertEquals()` where appropriate, to make the tests more reliable.

Follow-up to [48937], [48939], [48940], [48944].

See #38266.
Built from https://develop.svn.wordpress.org/trunk@49547


git-svn-id: http://core.svn.wordpress.org/trunk@49285 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.6-beta3-49546';
+$wp_version = '5.6-beta3-49547';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.