* RemoteFilesystemTest: simplifying some mock expectations calls
- will($this->returnValue()) to willReturn()
- will($this->returnCallBack()) to willReturnCallback()
* RemoteFilesystemTest: extracting identical mocks for IOInterface into a separate getIOInterfaceMock() method
* RemoteFilesystemTest: converting protected helper methods to private.
* RemoteFilesystemTest: moving getConfigMock() private method after the public methods (with other private methods)
* adding RemoteFileSystemTest::testCopyWithRetryAuthFailureFalse() unit test.
* Allow optional injecting of AuthHelper into RemoteFilesystem constructor.
* adding RemoteFileSystemTest::testCopyWithSuccessOnRetry() unit test.
* using backward compatible @expectedException in RemoteFilesystemTest.php
* RemoteFilesystemTest: extracting RemoteFilesystem with mocked method creation into a separate method.
* RemoteFilesystemTest: extracting AuthHelper with mocked method creation into a separate method.
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