ENH: Make warning testing context managers more specific

This means that warnings of different origin then the one tested for
behave normally. If the normal behaviour is to igonre them this might
decrease specificity in rare cases. In most cases the specificity
will be slightly higher.

3 files changed, 20 insertions, 15 deletions

diff --git a/doc/release/1.12.0-notes.rst b/doc/release/1.12.0-notes.rst
index 9a9a50aa8..7b315b90b 100644
--- a/doc/release/1.12.0-notes.rst
+++ b/doc/release/1.12.0-notes.rst
@@ -112,6 +112,18 @@ change in implementation some very delicate tests may fail that did not
 fail before.
 
 
+``assert_warns`` and ``deprecated`` decorator more specific
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The ``assert_warns`` function and context manager are now more specific
+to the given warning category. This increased specificity leads to them
+being handled according to the outer warning settings. This means that
+no warning may be raised in cases where a wrong category warning is given
+and ignored outside the context. Alternatively the increased specificity
+may mean that warnings that were incorrectly ignored will now be shown
+or raised. See also the new ``suppress_warnings`` context manager.
+The same is true for the ``deprecated`` decorator.
+
+
 C API
 ~~~~~
 
diff --git a/numpy/testing/tests/test_utils.py b/numpy/testing/tests/test_utils.py
index c0f609883..c191aea5b 100644
--- a/numpy/testing/tests/test_utils.py
+++ b/numpy/testing/tests/test_utils.py
@@ -503,23 +503,21 @@ class TestWarns(unittest.TestCase):
             warnings.warn("yo", DeprecationWarning)
 
         failed = False
-        filters = sys.modules['warnings'].filters[:]
-        try:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error", DeprecationWarning)
             try:
-                # Should raise an AssertionError
+                # Should raise a DeprecationWarning
                 assert_warns(UserWarning, f)
                 failed = True
-            except AssertionError:
+            except DeprecationWarning:
                 pass
-        finally:
-            sys.modules['warnings'].filters = filters
 
         if failed:
             raise AssertionError("wrong warning caught by assert_warn")
 
 
 class TestAssertAllclose(unittest.TestCase):
-    
+
     def test_simple(self):
         x = 1e-3
         y = 1e-9
diff --git a/numpy/testing/utils.py b/numpy/testing/utils.py
index c7f4a0aa7..8789dd13c 100644
--- a/numpy/testing/utils.py
+++ b/numpy/testing/utils.py
@@ -1658,16 +1658,12 @@ class WarningManager(object):
 @contextlib.contextmanager
 def _assert_warns_context(warning_class, name=None):
     __tracebackhide__ = True  # Hide traceback for py.test
-    with warnings.catch_warnings(record=True) as l:
-        warnings.simplefilter('always')
+    with suppress_warnings() as sup:
+        l = sup.record(warning_class)
         yield
         if not len(l) > 0:
             name_str = " when calling %s" % name if name is not None else ""
             raise AssertionError("No warning raised" + name_str)
-        if not l[0].category is warning_class:
-            name_str = "%s " % name if name is not None else ""
-            raise AssertionError("First warning %sis not a %s (is %s)"
-                                 % (name_str, warning_class, l[0]))
 
 
 def assert_warns(warning_class, *args, **kwargs):
@@ -1676,8 +1672,7 @@ def assert_warns(warning_class, *args, **kwargs):
 
     A warning of class warning_class should be thrown by the callable when
     invoked with arguments args and keyword arguments kwargs.
-    If a different type of warning is thrown, it will not be caught, and the
-    test case will be deemed to have suffered an error.
+    If a different type of warning is thrown, it will not be caught.
 
     If called with all arguments other than the warning class omitted, may be
     used as a context manager: