kata01-mars-rover

1. Inspired by Jason Gorman in his TDD videos series Test-Driven Development (TDD) in Python #4 - Duplication & The Rule of Three) I decided to follow along his video and implement my own version of Mars Rover Kata.

2. Implemented Mars Rover Kata using Python and following TDD. Kata requirements can be found here https://kata-log.rocks/mars-rover-kata.

3. Takeaways 3.1 Usage of @parameterized.expand([]) to parameterized tests. A best practice that can be handy is:

• parameterized should follow AAA from left to righ (Arrange, Act, Assert), there could be more than Aparameter per section. As you can see in the example bellow there are two Arrange pre-conditions (Compass and Point), one Act (MoveCommand) and one Assert (Point)

   @parameterized.expand([
        (Compass.S,  Point(0,0), MoveCommand.FORWARD, Point(0, 1)),
        (Compass.S,  Point(1,1), MoveCommand.BACKWARD, Point(1, 0)),
        (Compass.E,  Point(0,0), MoveCommand.FORWARD, Point(1, 0)),
        (Compass.E,  Point(1,1), MoveCommand.BACKWARD, Point(0, 1)),
    ])
    def test04_move_commands(self, initial_facing, initial_point, move_command, ends_position):
        #Arrange
        mars_rover = MarsRover(initial_point, initial_facing)
        #Act
        mars_rover.move(move_command)
        #Assert
        self.assertTrue(mars_rover.current_position() == ends_position)

3.2 Another takeaway is the usage of dictionaries and pattern matching as awesome replacement for switch statements:

     def check_boundaries(self, move_command):
        return {
            (Compass.N, MoveCommand.FORWARD):  self._current_position.y > 0,
            (Compass.N, MoveCommand.BACKWARD): self._current_position.y < 10,
            (Compass.S, MoveCommand.FORWARD):  self._current_position.y < 10,
            (Compass.S, MoveCommand.BACKWARD): self._current_position.y > 0,
            (Compass.E, MoveCommand.FORWARD):  self._current_position.x < 10,
            (Compass.E, MoveCommand.BACKWARD): self._current_position.x > 0,
            (Compass.W, MoveCommand.FORWARD):  self._current_position.x > 0,
            (Compass.W, MoveCommand.BACKWARD): self._current_position.x < 10
        }[(self.direction, move_command)]

Usage:

    if self.check_boundaries(move_command):

How it works

It could be hard to understand how it works for those non-pythonist (like myself). I will try to explain it below. For sake of simplicity I will focused only in one case:

Non-pythonic way:

    def check_boundaries(self, move_command):
        if self.direction == Compass.N and move_command == MoveCommand.FORWARD:
            if self._current_position.y > 0:
               return true
             else
                return flase

Pythonic way:

    def check_boundaries(self, move_command):
        return {
            (Compass.N, MoveCommand.FORWARD):  self._current_position.y > 0
            }

4. Music to help you out staying in the zone x-team radio

Authors

• Matias Tripode - Initial work - My profile in Linkedin

License

This project is licensed under the MIT License - see the LICENSE.md file for details

Acknowledgments

• Jason Gorman for his great content in youtube Codemanship
• Hernan Wilkinson for inspiring me to learn TDD 10pines