Cache\PhpBackend::removeBin() does not remove the bin

I added the following test to GenericCacheBackendUnitTest.php:

 /**
   * Test Drupal\Core\Cache\CacheBackendInterface::removeBin().
   */
  public function testRemoveBin() {
    $backend = $this->getCacheBackend();
    $unrelated = $this->getCacheBackend('bootstrap');

    // Set both expiring and permanent keys.
    $backend->set('test1', 1, Cache::PERMANENT);
    $backend->set('test2', 3, time() + 1000);
    $unrelated->set('test3', 4, Cache::PERMANENT);

    $backend->removeBin();

    $this->assertFalse($backend->get('test1'), 'First key has been deleted.');
    $this->assertFalse($backend->get('test2'), 'Second key has been deleted.');
    $this->assertTrue($unrelated->get('test3'), 'Item in other bin is preserved.');
  }

The test initially failed, then passed after the patch was applied, but I'm a little wary that I reverse engineered an outcome so more reviewers would be good.

+++ b/core/modules/system/src/Tests/Cache/GenericCacheBackendUnitTestBase.php
@@ -666,4 +666,23 @@ public function testInvalidateAll() {
+    $backend = $this->getCacheBackend();
+    $unrelated = $this->getCacheBackend('bootstrap');
...
+    $this->assertFalse($backend->get('test1'), 'First key has been deleted.');
+    $this->assertFalse($backend->get('test2', TRUE), 'Second key has been deleted.');
+    $this->assertTrue($unrelated->get('test3'), 'Item in other bin is preserved.');

Test looks good, but $unrelated is a bit a strange name, maybe renamed to $backend_a and $backend_b?

Tagging novice to update this.

Please review :)

You renamed it in the existing testDeleteAll() method (now I see where that came from), but not in the new test method testRemoveBin() :)

On two more method! :D

Great, looks good now.

This issue is a normal bug fix, and doesn't include any disruptive changes, so it is allowed per https://www.drupal.org/core/beta-changes. Committed 87be19c and pushed to 8.0.x. Thanks!