test all files with doctest

This runs doctest on .py and rst files.
See #443

src/icalendar/tests/test_with_doctest.py

@@ -0,0 +1,64 @@
+"""This file tests the source code provided by the documentation.
+
+See 
+- doctest documentation: https://docs.python.org/3/library/doctest.html
+- Issue 443: https://github.com/collective/icalendar/issues/443
+
+This file should be tests, too:
+
+    >>> print("Hello World!")
+    Hello World!
+
+"""
+import doctest
+import os
+import pytest
+import importlib
+
+HERE = os.path.dirname(__file__) or "."
+ICALENDAR_PATH = os.path.dirname(HERE)
+
+PYTHON_FILES = [
+    os.path.join(dirpath, filename)
+    for dirpath, dirnames, filenames in os.walk(ICALENDAR_PATH)
+    for filename in filenames if filename.lower().endswith(".py")
+]
+
+MODULE_NAMES = [
+    "icalendar" + python_file[len(ICALENDAR_PATH):-3].replace("/", ".")
+    for python_file in PYTHON_FILES
+]
+
+def test_this_module_is_among_them():
+    assert __name__ in MODULE_NAMES
+
+@pytest.mark.parametrize("module_name", MODULE_NAMES)
+def test_docstring_of_python_file(module_name):
+    """This test runs doctest on the Python module."""
+    module = importlib.import_module(module_name)
+    test_result = doctest.testmod(module, name=module_name)
+    assert test_result.failed == 0
+
+DOCUMENTATION_PATH = os.path.join(HERE, "../../../")
+
+DOCUMENT_PATHS = [
+    os.path.join(dirpath, filename)
+    for dirpath, dirnames, filenames in os.walk(DOCUMENTATION_PATH)
+    for filename in filenames if filename.lower().endswith(".rst")
+]
+
+@pytest.mark.parametrize("filename", [
+    "README.rst",
+    "index.rst",
+])
+def test_files_is_included(filename):
+    assert any(path.endswith(filename) for path in DOCUMENT_PATHS)
+
+@pytest.mark.parametrize("document", DOCUMENT_PATHS)
+def test_documentation_file(document):
+    """This test runs doctest on a documentation file."""
+    test_result = doctest.testfile(document, module_relative=False)
+    assert test_result.failed == 0
+
+
+

tox.ini

@@ -10,6 +10,7 @@ usedevelop=True
 deps =
     pytest
     coverage
+    hypothesis
 commands =
     coverage run --source=src/icalendar --omit=*/tests/* --module pytest []
     coverage report