test.support: Added TestHandler and Matcher classes for better support of assertions about logging.

Lib/test/support.py

@@ -21,7 +21,7 @@ import subprocess
 import imp
 import time
 import sysconfig
-
+import logging.handlers
 
 try:
     import _thread
@@ -42,7 +42,8 @@ __all__ = [
     "set_memlimit", "bigmemtest", "bigaddrspacetest", "BasicTestRunner",
     "run_unittest", "run_doctest", "threading_setup", "threading_cleanup",
     "reap_children", "cpython_only", "check_impl_detail", "get_attribute",
-    "swap_item", "swap_attr", "requires_IEEE_754"]
+    "swap_item", "swap_attr", "requires_IEEE_754",
+    "TestHandler", "Matr]
 
 
 class Error(Exception):
@@ -1343,3 +1344,68 @@ def args_from_interpreter_flags():
         if v > 0:
             args.append('-' + opt * v)
     return args
+
+#============================================================
+# Support for assertions about logging.
+#============================================================
+
+class TestHandler(logging.handlers.BufferingHandler):
+    def __init__(self, matcher):
+        # BufferingHandler takes a "capacity" argument
+        # so as to know when to flush. As we're overriding
+        # shouldFlush anyway, we can set a capacity of zero.
+        # You can call flush() manually to clear out the
+        # buffer.
+        logging.handlers.BufferingHandler.__init__(self, 0)
+        self.matcher = matcher
+
+    def shouldFlush(self):
+        return False
+
+    def emit(self, record):
+        self.format(record)
+        self.buffer.append(record.__dict__)
+
+    def matches(self, **kwargs):
+        """
+        Look for a saved dict whose keys/values match the supplied arguments.
+        """
+        result = False
+        for d in self.buffer:
+            if self.matcher.matches(d, **kwargs):
+                result = True
+                break
+        return result
+
+class Matcher(object):
+
+    _partial_matches = ('msg', 'message')
+
+    def matches(self, d, **kwargs):
+        """
+        Try to match a single dict with the supplied arguments.
+
+        Keys whose values are strings and which are in self._partial_matches
+        will be checked for partial (i.e. substring) matches. You can extend
+        this scheme to (for example) do regular expression matching, etc.
+        """
+        result = True
+        for k in kwargs:
+            v = kwargs[k]
+            dv = d.get(k)
+            if not self.match_value(k, dv, v):
+                result = False
+                break
+        return result
+
+    def match_value(self, k, dv, v):
+        """
+        Try to match a single stored value (dv) with a supplied value (v).
+        """
+        if type(v) != type(dv):
+            result = False
+        elif type(dv) is not str or k not in self._partial_matches:
+            result = (v == dv)
+        else:
+            result = dv.find(v) >= 0
+        return result

Misc/NEWS

@@ -63,6 +63,9 @@ Core and Builtins
 Library
 -------
 
+- test.support: Added TestHandler and Matcher classes for better support of
+  assertions about logging.
+
 - Issue #4391: Use proper plural forms in argparse.
 
 - Issue #10601: sys.displayhook uses 'backslashreplace' error handler on