'``Certificates.add_node`` generates another node certificate.'

@skipUnless(which('flocker-ca'), 'flocker-ca    not    installed    (FLOC-2600)')
def test_add_node(self):

    output = FilePath(self.mktemp())
    output.makedirs()
    certificates = Certificates.generate(output, 'some-service', 2, 'test-cluster')
    certificates.add_node(3)
    self.assertEqual({output.child('cluster.crt'), output.child('cluster.key'), output.child('control-some-service.crt'), output.child('control-some-service.key'), output.child('user.crt'), output.child('user.key'), output.child('node-0.crt'), output.child('node-0.key'), output.child('node-1.crt'), output.child('node-1.key'), output.child('node-3.crt'), output.child('node-3.key')}, set(output.children()))
