'L{keys._getPersistentRSAKey} will put the key in
C{directory}/C{filename}, with the key length of C{keySize}.'

def test_providedArguments(self):

    tempDir = FilePath(self.mktemp())
    keyFile = tempDir.child('mykey.pem')
    key = keys._getPersistentRSAKey(keyFile, keySize=512)
    self.assertEqual(key.size(), 512)
    self.assertTrue(keyFile.exists())
