public function testCheckingKeyExistenceIsDelegatedToClient()
 {
     $key = 'key';
     $this->mockClient->method('exists')->with($key)->willReturn(true);
     $this->assertTrue($this->store->has($key));
 }
 public function testFalseIsReturnedIfKeyDoesNotExist()
 {
     $this->assertFalse($this->keyValueStore->has('foo'));
 }