Merge pull request #81 from MaxG87/master
Add property-based fuzz test
diff --git a/.gitignore b/.gitignore
index 413f6e2..69504d4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
*.egg
*.egg-info
*.py[cod]
+.hypothesis/
.tox
dist
diff --git a/test_mccabe.py b/test_mccabe.py
index b53db6a..fe6e8d3 100644
--- a/test_mccabe.py
+++ b/test_mccabe.py
@@ -1,11 +1,17 @@
import unittest
import sys
+
try:
from StringIO import StringIO
except ImportError:
from io import StringIO
import pytest
+try:
+ import hypothesmith
+ from hypothesis import HealthCheck, given, settings, strategies as st
+except ImportError:
+ hypothesmith = None
import mccabe
from mccabe import get_code_complexity
@@ -233,5 +239,41 @@
self.assertEqual(0, mccabe.get_module_complexity("mccabe.py"))
+# This test uses the Hypothesis and Hypothesmith libraries to generate random
+# syntatically-valid Python source code and applies McCabe on it.
+@settings(
+ max_examples=1000, # roughly 1k tests/minute, or half that under coverage
+ derandomize=False, # deterministic mode to avoid CI flakiness
+ deadline=None, # ignore Hypothesis' health checks; we already know that
+ suppress_health_check=HealthCheck.all(), # this is slow and filter-heavy.
+)
+@given(
+ # Note that while Hypothesmith might generate code unlike that written by
+ # humans, it's a general test that should pass for any *valid* source code.
+ # (so e.g. running it against code scraped of the internet might also help)
+ src_contents=hypothesmith.from_grammar() | hypothesmith.from_node(),
+ max_complexity=st.integers(min_value=1),
+)
+@pytest.mark.skipif(not hypothesmith, reason="hypothesmith could not be imported")
+def test_idempotent_any_syntatically_valid_python(
+ src_contents: str, max_complexity: int
+) -> None:
+ """Property-based tests for mccabe.
+
+ This test case is based on a similar test for Black, the code formatter.
+ Black's test was written by Zac Hatfield-Dodds, the author of Hypothesis
+ and the Hypothesmith tool for source code generation. You can run this
+ file with `python`, `pytest`, or (soon) a coverage-guided fuzzer Zac is
+ working on.
+ """
+
+ # Before starting, let's confirm that the input string is valid Python:
+ compile(src_contents, "<string>", "exec") # else bug is in hypothesmith
+
+ # Then try to apply get_complexity_number to the code...
+ get_code_complexity(src_contents, max_complexity)
+
+
if __name__ == "__main__":
+ test_idempotent_any_syntatically_valid_python()
unittest.main()
diff --git a/tox.ini b/tox.ini
index 6337825..5965f63 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,6 +5,8 @@
[testenv]
deps =
pytest
+ hypothesis ; python_version >= "3.6"
+ hypothesmith ; python_version >= "3.6"
commands =
pytest
