$expectedHash = hash( $algo, $contents );
$actualHash = FileContentsHasher::getFileContentsHash( $fileName, $algo );
$this->assertEquals( $expectedHash, $actualHash );
$expectedHash = hash( $algo, $contents );
$actualHash = FileContentsHasher::getFileContentsHash( $fileName, $algo );
$this->assertEquals( $expectedHash, $actualHash );