Add some tests and Travis integration

.gitignore

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+.pytest_cache/
+__pycache__/

.travis.yml

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+language: python
+
+python:
+  - 3.6
+
+install:
+  - pip install pytest pytest-pep8 pytest-flakes
+
+script:
+  - pytest --pep8 --flakes

test_mazes.py

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+"""
+Basic tests to ensure maze files are properly formatted.
+"""
+from pathlib import Path
+import re
+
+import pytest
+
+
+def parametrize_maze_files(maze_files):
+    return pytest.mark.parametrize('maze_file', maze_files,
+                                   ids=[str(x) for x in maze_files])
+
+
+CLASSIC_SIZE = 16
+HALFSIZE_SIZE = 32
+
+classic_mazes = list(Path('classic').glob('*'))
+halfsize_mazes = list(Path('halfsize').glob('*'))
+training_mazes = list(Path('training').glob('*'))
+competition_mazes = classic_mazes + halfsize_mazes
+all_mazes = classic_mazes + halfsize_mazes + training_mazes
+
+classic_mazes = parametrize_maze_files(classic_mazes)
+halfsize_mazes = parametrize_maze_files(halfsize_mazes)
+training_mazes = parametrize_maze_files(training_mazes)
+competition_mazes = parametrize_maze_files(competition_mazes)
+all_mazes = parametrize_maze_files(all_mazes)
+
+
+def read_maze(maze_file):
+    rows = maze_file.read_text().split('\n')
+    for i, row in enumerate(rows):
+        if not row.startswith(('o', '|')):
+            break
+    return rows[:i]
+
+
+@all_mazes
+def test_file_name(maze_file):
+    """
+    - All maze files must be text files with `.txt` extension.
+    - Only "a-z", "A-Z", "0-9", "-" and "_" characters are allowed.
+    """
+    assert maze_file.suffix == '.txt'
+    assert re.match('^[a-zA-Z0-9\-_]*$', maze_file.stem)
+
+
+@classic_mazes
+def test_classic_size(maze_file):
+    """
+    Classic maze size is always 16x16.
+    """
+    rows = read_maze(maze_file)
+    assert len(rows) == (CLASSIC_SIZE * 2 + 1)
+    assert all(len(row) == (CLASSIC_SIZE * 4 + 1) for row in rows)
+
+
+@halfsize_mazes
+def test_halfsize_size(maze_file):
+    """
+    Half-size maze size is always 32x32.
+    """
+    rows = read_maze(maze_file)
+    assert len(rows) == (HALFSIZE_SIZE * 2 + 1)
+    assert all(len(row) == (HALFSIZE_SIZE * 4 + 1) for row in rows)
+
+
+@training_mazes
+def test_training_size(maze_file):
+    """
+    Training maze size is the same as classic size, even if not fully used.
+    """
+    rows = read_maze(maze_file)
+    assert len(rows) == (CLASSIC_SIZE * 2 + 1)
+    assert all(len(row) == (CLASSIC_SIZE * 4 + 1) for row in rows)
+
+
+@all_mazes
+def test_format(maze_file):
+    """
+    Maze file format must be homogeneous. Vertical walls are represented with
+    a `|`, horizontal walls with `---` and posts with `o`.
+
+    Even rows must:
+
+    - Have a post each 4 characters.
+    - Have a wall `---` or nothing `   ` between posts.
+
+    Odd rows must:
+
+    - Have a wall `|` or nothing ` ` each 4 characters.
+    """
+    rows = read_maze(maze_file)
+    even_rows = rows[::2]
+    assert all(all(x == 'o' for x in row[::4]) for row in even_rows)
+    assert all(all(x in ('---', '   ') for x in row.strip('o').split('o'))
+               for row in even_rows)
+    odd_rows = rows[1::2]
+    assert all(all(x in ('|', ' ') for x in row[::4]) for row in odd_rows)
+
+
+@all_mazes
+def test_boundaries(maze_file):
+    """
+    Maze boundaries are expected to be closed.
+    """
+    rows = read_maze(maze_file)
+    east_boundary = [row[-1] for row in rows[1::2]]
+    west_boundary = [row[0] for row in rows[1::2]]
+    assert all(v == '|' for v in east_boundary + west_boundary)
+    north_boundary = rows[0].strip('o').split('o')
+    south_boundary = rows[-1].strip('o').split('o')
+    assert all(h == '---' for h in north_boundary + south_boundary)
+
+
+@competition_mazes
+def test_starting_cell(maze_file):
+    """
+    The starting cell is expected to be at the South-West and facing North.
+    """
+    rows = read_maze(maze_file)
+    assert rows[-3][:5] == 'o   o'
+    assert rows[-2][:5] == '|   |'
+    assert rows[-1][:5] == 'o---o'