Implement ExceptionInfo.match() to match regexp on str(exception)

This implements similar functionality to
unittest.TestCase.assertRegexpMatches()

closes #372

CHANGELOG.rst

@@ -18,6 +18,10 @@
 * New Add ability to add global properties in the final xunit output file.
   Thanks `@tareqalayan`_ for the complete PR `#1454`_).
 
+* New ``ExceptionInfo.match()`` method to match a regular expression on the
+  string representation of an exception. Closes proposal `#372`_.
+  Thanks `@omarkohl`_ for the complete PR (`#1502`_) and `@nicoddemus`_ for the
+  implementation tips.
 
 *
 
@@ -38,6 +42,7 @@
 .. _@kalekundert: https://github.com/kalekundert
 .. _@tareqalayan: https://github.com/tareqalayan
 .. _@palaviv: https://github.com/palaviv
+.. _@omarkohl: https://github.com/omarkohl
 
 .. _#1428: https://github.com/pytest-dev/pytest/pull/1428
 .. _#1444: https://github.com/pytest-dev/pytest/pull/1444
@@ -45,6 +50,8 @@
 .. _#1454: https://github.com/pytest-dev/pytest/pull/1454
 .. _#1468: https://github.com/pytest-dev/pytest/pull/1468
 .. _#1474: https://github.com/pytest-dev/pytest/pull/1474
+.. _#1502: https://github.com/pytest-dev/pytest/pull/1502
+.. _#372: https://github.com/pytest-dev/pytest/issues/372
 
 
 2.9.2.dev1

_pytest/_code/code.py

@@ -1,5 +1,6 @@
 import sys
 from inspect import CO_VARARGS, CO_VARKEYWORDS
+import re
 
 import py
 
@@ -427,6 +428,19 @@ class ExceptionInfo(object):
         loc = ReprFileLocation(entry.path, entry.lineno + 1, self.exconly())
         return unicode(loc)
 
+    def match(self, regexp):
+        """
+        Match the regular expression 'regexp' on the string representation of
+        the exception. If it matches then True is returned (so that it is
+        possible to write 'assert excinfo.match()'). If it doesn't match an
+        AssertionError is raised.
+        """
+        __tracebackhide__ = True
+        if not re.search(regexp, str(self.value)):
+            assert 0, "Pattern '{0!s}' not found in '{1!s}'".format(
+                regexp, self.value)
+        return True
+
 
 class FormattedExcinfo(object):
     """ presenting information about failing Functions and Generators. """

doc/en/assert.rst

@@ -110,6 +110,24 @@ exceptions your own code is deliberately raising, whereas using
 like documenting unfixed bugs (where the test describes what "should" happen)
 or bugs in dependencies.
 
+If you want to test that a regular expression matches on the string
+representation of an exception (like the ``TestCase.assertRaisesRegexp`` method
+from ``unittest``) you can use the ``ExceptionInfo.match`` method::
+
+    import pytest
+
+    def myfunc():
+        raise ValueError("Exception 123 raised")
+
+    def test_match():
+        with pytest.raises(ValueError) as excinfo:
+            myfunc()
+        excinfo.match(r'.* 123 .*')
+
+The regexp parameter of the ``match`` method is matched with the ``re.search``
+function. So in the above example ``excinfo.match('123')`` would have worked as
+well.
+
 
 .. _`assertwarns`:
 

testing/code/test_excinfo.py

@@ -323,6 +323,25 @@ def test_codepath_Queue_example():
     assert path.basename.lower() == "queue.py"
     assert path.check()
 
+def test_match_succeeds():
+    with pytest.raises(ZeroDivisionError) as excinfo:
+        0 / 0
+    excinfo.match(r'.*zero.*')
+
+def test_match_raises_error(testdir):
+    testdir.makepyfile("""
+        import pytest
+        def test_division_zero():
+            with pytest.raises(ZeroDivisionError) as excinfo:
+                0 / 0
+            excinfo.match(r'[123]+')
+    """)
+    result = testdir.runpytest()
+    assert result.ret != 0
+    result.stdout.fnmatch_lines([
+        "*AssertionError*Pattern*[123]*not found*",
+    ])
+
 class TestFormattedExcinfo:
     def pytest_funcarg__importasmod(self, request):
         def importasmod(source):