public function test_delete_many()
 {
     $this->assertTrue($this->store->set('foo', 'bar'));
     $this->assertTrue($this->store->set('bat', 'baz'));
     $this->assertTrue($this->store->set('this', 'that'));
     $keys = array('foo', 'bat');
     $this->assertEquals(2, $this->store->delete_many($keys));
     // The $keys is modified in delete_many, ensure it does not change out here.
     $this->assertEquals(array('foo', 'bat'), $keys);
     $this->assertEquals('that', $this->store->get('this'));
     $this->assertFalse($this->store->get('foo'));
     $this->assertFalse($this->store->get('bat'));
 }