def test_layer(self):
        n_inputs = 10
        n_hidden = 20

        x = tf.ones([1, n_inputs])
        input_layer = Layer(n_units=n_inputs, activation=x)

        nn = NeuralNetwork(input_layer)
        self.assertEqual(nn.size(), 1)

        # add a layer with biases
        hidden_layer = Layer(n_hidden, activation=tf.identity)
        nn.add_layer(hidden_layer, biased=True)

        layer_0 = nn.layer(0)
        layer_1 = nn.layer(1)

        self.assertEqual(layer_0, input_layer)
        self.assertEqual(layer_1, hidden_layer)