Add algorithm for testing Project Euler solutions

.travis.yml

@@ -12,6 +12,7 @@ jobs:
         - black --check . || true 
         - flake8 --ignore=E203,W503 --max-complexity=25 --max-line-length=88 --statistics --count .
         - scripts/validate_filenames.py  # no uppercase, no spaces, in a directory
+        - project_euler/solution_test.py  # test project Euler solutions
         - pip install -r requirements.txt  # fast fail on black, flake8, validate_filenames
       script:
         - mypy --ignore-missing-imports . || true  # https://github.com/python/mypy/issues/7907

project_euler/solution_test.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+import importlib.util
+import logging
+import pathlib
+
+LOG_FILENAME = "project_euler_test.log"
+
+# Keep the answer part in str for consistency as some problems could output in str
+# Problem 329: 199740353/29386561536000 (Format for this answer is a/b)
+# https://github.com/nayuki/Project-Euler-solutions/blob/master/Answers.txt#L191
+ANSWERS = {
+    1: "233168",
+    2: "4613732",
+    3: "6857",
+    4: "906609",
+    5: "232792560",
+    6: "25164150",
+    7: "104743",
+    8: "23514624000",
+    9: "31875000",
+    10: "142913828922",
+    11: "70600674",
+    12: "76576500",
+    13: "5537376230",
+    14: "837799",
+    15: "137846528820",
+    16: "1366",
+    17: "21124",
+    18: "1074",
+    19: "171",
+}
+
+WORKING_DIR = pathlib.Path.cwd()
+
+if WORKING_DIR.name == "Python":
+    PROJECT_EULER_PATH = WORKING_DIR.joinpath("project_euler")
+# Below two checks are just in case something goes wrong
+# Travis root dir = /home/travis/build/TheAlgorithms/Python
+# https://travis-ci.com/github/TheAlgorithms/Python/builds/186187397#L398
+elif WORKING_DIR.name == "TheAlgorithms":
+    PROJECT_EULER_PATH = WORKING_DIR.joinpath("Python", "project_euler")
+elif WORKING_DIR.name == "project_euler":
+    PROJECT_EULER_PATH = WORKING_DIR
+
+# Remove previous log file if present
+pathlib.Path.unlink(WORKING_DIR.joinpath(LOG_FILENAME), missing_ok=True)
+
+# This should be after removing the log file if present
+logging.basicConfig(
+    filename=LOG_FILENAME, format="%(levelname)s: %(message)s", level=logging.DEBUG,
+)
+
+
+def generate_solution_modules(dir_path: pathlib.Path):
+    # Iterating over every file or directory
+    for file_path in dir_path.iterdir():
+        if file_path.suffix != ".py" or file_path.name.startswith(("_", "test")):
+            continue
+        # Importing the source file through the given path
+        # https://docs.python.org/3/library/importlib.html#importing-a-source-file-directly
+        spec = importlib.util.spec_from_file_location(file_path.name, str(file_path))
+        module = importlib.util.module_from_spec(spec)
+        spec.loader.exec_module(module)
+        yield module
+
+
+def test_project_euler():
+    for problem_number, expected in ANSWERS.items():
+        problem_dir = PROJECT_EULER_PATH.joinpath(f"problem_{problem_number:02}")
+        # By checking if it's a directory we can write all the problem number and
+        # answer pair in ANSWERS variable and not worry whether it is actually
+        # present in the 'project_euler' directory
+        if problem_dir.is_dir():
+            for solution_module in generate_solution_modules(problem_dir):
+                try:
+                    answer = str(solution_module.solution())
+                    assert answer == expected, f"Expected: {expected} but got {answer}"
+                # TypeError: If solution() requires arguments
+                # AssertionError: If answer is incorrect
+                # AttributeError: If the module has no attribute called 'solution'
+                except (AssertionError, AttributeError, TypeError) as err:
+                    logging.error(
+                        f"{err} \nSource: Problem {problem_number}: "
+                        f"{solution_module.__name__}\n"
+                    )
+
+
+if __name__ == "__main__":
+    test_project_euler()