Added logging output support to unittests

tests/__init__.py

@@ -1,4 +1,8 @@
 import os, sys
+import param
+import logging
+
+from holoviews.element.comparison import ComparisonTestCase
 
 try:
     # Standardize backend due to random inconsistencies
@@ -9,3 +13,77 @@
 
 cwd = os.path.abspath(os.path.split(__file__)[0])
 sys.path.insert(0, os.path.join(cwd, '..'))
+
+
+class MockLoggingHandler(logging.Handler):
+    """
+    Mock logging handler to check for expected logs used by
+    LoggingComparisonTestCase.
+
+    Messages are available from an instance's ``messages`` dict, in
+    order, indexed by a lowercase log level string (e.g., 'debug',
+    'info', etc.)."""
+
+    def __init__(self, *args, **kwargs):
+        self.messages = {'DEBUG': [], 'INFO': [], 'WARNING': [],
+                         'ERROR': [], 'CRITICAL': [], 'VERBOSE':[]}
+        super(MockLoggingHandler, self).__init__(*args, **kwargs)
+
+    def emit(self, record):
+        "Store a message to the instance's messages dictionary"
+        self.acquire()
+        try:
+            self.messages[record.levelname].append(record.getMessage())
+        finally:
+            self.release()
+
+    def reset(self):
+        self.acquire()
+        try:
+            for message_list in self.messages.values():
+                message_list = []
+        finally:
+            self.release()
+
+    def tail(self, level, n=1):
+        "Returns the last n lines captured at the given level"
+        return [str(el) for el in self.messages[level][-n:]]
+
+    def assertEndsWith(self, level, substring):
+        """
+        Assert that the last line captured at the given level ends with
+        a particular substring.
+        """
+        methods = {'WARNING':'param.warning()', 'INFO':'param.message()',
+                   'VERBOSE':'param.verbose()', 'DEBUG':'param.debug()'}
+        msg='\n\n{method}: {last_line}\ndoes not end with:\n{substring}'
+        last_line = self.tail(level, n=1)
+        if len(last_line) == 0:
+            raise AssertionError('Missing {method} output: {repr(substring)}'.format(
+                method=methods[level], substring=repr(substring)))
+        if not last_line[0].endswith(substring):
+            raise AssertionError(msg.format(method=methods[level],
+                                            last_line=repr(last_line[0]),
+                                            substring=repr(substring)))
+
+
+
+class LoggingComparisonTestCase(ComparisonTestCase):
+    """
+    ComparisonTestCase with support for capturing param logging output.
+
+    Subclasses must call super setUp to make the
+    tests independent. Testing can then be done via the
+    self.log_handler.tail and self.log_handler.assertEndsWith methods.
+    """
+
+    @classmethod
+    def setUpClass(cls):
+        super(LoggingComparisonTestCase, cls).setUpClass()
+        log = param.parameterized.get_logger()
+        cls.log_handler = MockLoggingHandler(level='DEBUG')
+        log.addHandler(cls.log_handler)
+
+    def setUp(self):
+        super(LoggingComparisonTestCase, self).setUp()
+        self.log_handler.reset()

tests/testdimensions.py

@@ -4,14 +4,18 @@
 from unittest import SkipTest
 from holoviews.core import Dimensioned, Dimension
 from holoviews.element.comparison import ComparisonTestCase
+from . import LoggingComparisonTestCase
 
 import numpy as np
 try:
     import pandas as pd
 except:
     pd = None
 
-class DimensionNameLabelTest(ComparisonTestCase):
+class DimensionNameLabelTest(LoggingComparisonTestCase):
+
+    def setUp(self):
+        super(DimensionNameLabelTest, self).setUp()
 
     def test_dimension_name(self):
         dim = Dimension('test')
@@ -35,8 +39,9 @@ def test_dimension_label_kwarg(self):
         self.assertEqual(dim.label, 'A test')
 
     def test_dimension_label_kwarg_and_tuple(self):
-        # Should work but issue a warning
         dim = Dimension(('test', 'A test'), label='Another test')
+        substr = "Using label as supplied by keyword ('Another test'), ignoring tuple value 'A test'"
+        self.log_handler.assertEndsWith('WARNING', substr)
         self.assertEqual(dim.label, 'Another test')
 
     def test_dimension_invalid_name(self):

tests/testdynamic.py

@@ -399,7 +399,7 @@ def callback():
         self.assertEqual(list(grid.keys()), [(i, j) for i in range(1, 3)
                                              for j in range(1, 3)])
         self.assertEqual(grid[(0, 1)][()], Image(np.array([[1, 1], [2, 3]])))
-    
+
     def test_dynamic_collate_grid_with_integer_stream_mapping(self):
         def callback():
             return GridSpace({(i, j): Image(np.array([[i, j], [2, 3]]))