changeset 26842:0f76c64f5cc3

testing: add hypothesis fuzz testing

Hypothesis a library for adding fuzzing over a range of structure
data to your test suite: http://hypothesis.readthedocs.org/en/latest/

This adds the ability to build tests using Hypothesis within the Mercurial test
suite. New tests and fixes using this helpers comes in later changesets.

--- a/tests/hghave.py	Mon Nov 02 13:00:45 2015 +0000
+++ b/tests/hghave.py	Sat Oct 24 12:46:03 2015 +0100
@@ -463,3 +463,12 @@
 @check("slow", "allow slow tests")
 def has_slow():
     return os.environ.get('HGTEST_SLOW') == 'slow'
+
+@check("hypothesis", "is Hypothesis installed")
+def has_hypothesis():
+    try:
+        import hypothesis
+        hypothesis.given
+        return True
+    except ImportError:
+        return False

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/hypothesishelpers.py	Sat Oct 24 12:46:03 2015 +0100
@@ -0,0 +1,62 @@
+# Helper module to use the Hypothesis tool in tests
+#
+# Copyright 2015 David R. MacIver
+#
+# For details see http://hypothesis.readthedocs.org
+
+import os
+import sys
+import traceback
+
+from hypothesis.settings import set_hypothesis_home_dir
+import hypothesis.strategies as st
+from hypothesis import given, Settings
+
+# hypothesis store data regarding generate example and code
+set_hypothesis_home_dir(os.path.join(
+    os.getenv('TESTTMP'), ".hypothesis"
+))
+
+def check(*args, **kwargs):
+    """decorator to make a function a hypothesis test
+
+    Decorated function are run immediately (to be used doctest style)"""
+    def accept(f):
+        # Workaround for https://github.com/DRMacIver/hypothesis/issues/206
+        # Fixed in version 1.13 (released 2015 october 29th)
+        f.__module__ = '__anon__'
+        try:
+            given(*args, settings=Settings(max_examples=2000), **kwargs)(f)()
+        except Exception:
+            traceback.print_exc(file=sys.stdout)
+            sys.exit(1)
+    return accept
+
+
+def roundtrips(data, decode, encode):
+    """helper to tests function that must do proper encode/decode roundtripping
+    """
+    @given(data)
+    def testroundtrips(value):
+        encoded = encode(value)
+        decoded = decode(encoded)
+        if decoded != value:
+            raise ValueError(
+                "Round trip failed: %s(%r) -> %s(%r) -> %r" % (
+                    encode.__name__, value, decode.__name__, encoded,
+                    decoded
+                ))
+    try:
+        testroundtrips()
+    except Exception:
+        # heredoc swallow traceback, we work around it
+        traceback.print_exc(file=sys.stdout)
+        raise
+    print("Round trip OK")
+
+
+# strategy for generating bytestring that might be an issue for Mercurial
+bytestrings = (
+    st.builds(lambda s, e: s.encode(e), st.text(), st.sampled_from([
+        'utf-8', 'utf-16',
+    ]))) | st.binary()