python/exercises/practice/react/react_test.py

from functools import partial

import unittest

from react import (
    InputCell,
    ComputeCell,
)

# Tests adapted from `problem-specifications//canonical-data.json`


class ReactTest(unittest.TestCase):
    def test_input_cells_have_a_value(self):
        input = InputCell(10)
        self.assertEqual(input.value, 10)

    def test_an_input_cell_s_value_can_be_set(self):
        input = InputCell(4)
        input.value = 20
        self.assertEqual(input.value, 20)

    def test_compute_cells_calculate_initial_value(self):
        input = InputCell(1)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        self.assertEqual(output.value, 2)

    def test_compute_cells_take_inputs_in_the_right_order(self):
        one = InputCell(1)
        two = InputCell(2)
        output = ComputeCell(
            [
                one,
                two,
            ],
            lambda inputs: inputs[0] + inputs[1] * 10,
        )
        self.assertEqual(output.value, 21)

    def test_compute_cells_update_value_when_dependencies_are_changed(self):
        input = InputCell(1)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        input.value = 3
        self.assertEqual(output.value, 4)

    def test_compute_cells_can_depend_on_other_compute_cells(self):
        input = InputCell(1)
        times_two = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] * 2,
        )
        times_thirty = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] * 30,
        )
        output = ComputeCell(
            [
                times_two,
                times_thirty,
            ],
            lambda inputs: inputs[0] + inputs[1],
        )
        self.assertEqual(output.value, 32)
        input.value = 3
        self.assertEqual(output.value, 96)

    def test_compute_cells_fire_callbacks(self):
        input = InputCell(1)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        cb1_observer = []
        callback1 = self.callback_factory(cb1_observer)
        output.add_callback(callback1)
        input.value = 3
        self.assertEqual(cb1_observer[-1], 4)

    def test_callback_cells_only_fire_on_change(self):
        input = InputCell(1)
        output = ComputeCell([input], lambda inputs: 111 if inputs[0] < 3 else 222)
        cb1_observer = []
        callback1 = self.callback_factory(cb1_observer)
        output.add_callback(callback1)
        input.value = 2
        self.assertEqual(cb1_observer, [])
        input.value = 4
        self.assertEqual(cb1_observer[-1], 222)

    def test_callbacks_do_not_report_already_reported_values(self):
        input = InputCell(1)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        cb1_observer = []
        callback1 = self.callback_factory(cb1_observer)
        output.add_callback(callback1)
        input.value = 2
        self.assertEqual(cb1_observer[-1], 3)
        input.value = 3
        self.assertEqual(cb1_observer[-1], 4)

    def test_callbacks_can_fire_from_multiple_cells(self):
        input = InputCell(1)
        plus_one = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        minus_one = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] - 1,
        )
        cb1_observer = []
        cb2_observer = []
        callback1 = self.callback_factory(cb1_observer)
        callback2 = self.callback_factory(cb2_observer)
        plus_one.add_callback(callback1)
        minus_one.add_callback(callback2)
        input.value = 10
        self.assertEqual(cb1_observer[-1], 11)
        self.assertEqual(cb2_observer[-1], 9)

    def test_callbacks_can_be_added_and_removed(self):
        input = InputCell(11)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        cb1_observer = []
        cb2_observer = []
        cb3_observer = []
        callback1 = self.callback_factory(cb1_observer)
        callback2 = self.callback_factory(cb2_observer)
        callback3 = self.callback_factory(cb3_observer)
        output.add_callback(callback1)
        output.add_callback(callback2)
        input.value = 31
        self.assertEqual(cb1_observer[-1], 32)
        self.assertEqual(cb2_observer[-1], 32)
        output.remove_callback(callback1)
        output.add_callback(callback3)
        input.value = 41
        self.assertEqual(len(cb1_observer), 1)
        self.assertEqual(cb2_observer[-1], 42)
        self.assertEqual(cb3_observer[-1], 42)

    def test_removing_a_callback_multiple_times_doesn_t_interfere_with_other_callbacks(
        self,
    ):
        input = InputCell(1)
        output = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        cb1_observer = []
        cb2_observer = []
        callback1 = self.callback_factory(cb1_observer)
        callback2 = self.callback_factory(cb2_observer)
        output.add_callback(callback1)
        output.add_callback(callback2)
        output.remove_callback(callback1)
        output.remove_callback(callback1)
        output.remove_callback(callback1)
        input.value = 2
        self.assertEqual(cb1_observer, [])
        self.assertEqual(cb2_observer[-1], 3)

    def test_callbacks_should_only_be_called_once_even_if_multiple_dependencies_change(
        self,
    ):
        input = InputCell(1)
        plus_one = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        minus_one1 = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] - 1,
        )
        minus_one2 = ComputeCell(
            [
                minus_one1,
            ],
            lambda inputs: inputs[0] - 1,
        )
        output = ComputeCell(
            [
                plus_one,
                minus_one2,
            ],
            lambda inputs: inputs[0] * inputs[1],
        )
        cb1_observer = []
        callback1 = self.callback_factory(cb1_observer)
        output.add_callback(callback1)
        input.value = 4
        self.assertEqual(cb1_observer[-1], 10)

    def test_callbacks_should_not_be_called_if_dependencies_change_but_output_value_doesn_t_change(
        self,
    ):
        input = InputCell(1)
        plus_one = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] + 1,
        )
        minus_one = ComputeCell(
            [
                input,
            ],
            lambda inputs: inputs[0] - 1,
        )
        always_two = ComputeCell(
            [
                plus_one,
                minus_one,
            ],
            lambda inputs: inputs[0] - inputs[1],
        )
        cb1_observer = []
        callback1 = self.callback_factory(cb1_observer)
        always_two.add_callback(callback1)
        input.value = 2
        self.assertEqual(cb1_observer, [])
        input.value = 3
        self.assertEqual(cb1_observer, [])
        input.value = 4
        self.assertEqual(cb1_observer, [])
        input.value = 5
        self.assertEqual(cb1_observer, [])

    # Utility functions.
    def callback_factory(self, observer):
        def callback(observer, value):
            observer.append(value)

        return partial(callback, observer)