1 files changed, 67 insertions, 0 deletions
diff --git a/tests/base.py b/tests/base.py
new file mode 100644
index 000000000..029a249ed
--- /dev/null
+++ b/tests/base.py
@@ -0,0 +1,67 @@
+import logging
+import unittest
+from contextlib import contextmanager
+
+
+class _CaptureLogHandler(logging.Handler):
+    """
+    A logging handler capturing all (raw and formatted) logging output.
+    """
+
+    def __init__(self):
+        super().__init__()
+        self.records = []
+
+    def emit(self, record):
+        self.records.append(record)
+
+
+class LoggingTestCase(unittest.TestCase):
+    """TestCase subclass that adds more logging assertion tools."""
+
+    @contextmanager
+    def assertNotLogs(self, logger=None, level=None, msg=None):
+        """
+        Asserts that no logs of `level` and higher were emitted by `logger`.
+
+        You can specify a specific `logger`, the minimum `logging` level we want to watch and a
+        custom `msg` to be added to the `AssertionError` if thrown. If the assertion fails, the
+        recorded log records will be outputted with the `AssertionError` message. The context
+        manager does not yield a live `look` into the logging records, since we use this context
+        manager when we're testing under the assumption that no log records will be emitted.
+        """
+        if not isinstance(logger, logging.Logger):
+            logger = logging.getLogger(logger)
+
+        if level:
+            level = logging._nameToLevel.get(level, level)
+        else:
+            level = logging.INFO
+
+        handler = _CaptureLogHandler()
+        old_handlers = logger.handlers[:]
+        old_level = logger.level
+        old_propagate = logger.propagate
+
+        logger.handlers = [handler]
+        logger.setLevel(level)
+        logger.propagate = False
+
+        try:
+            yield
+        except Exception as exc:
+            raise exc
+        finally:
+            logger.handlers = old_handlers
+            logger.propagate = old_propagate
+            logger.setLevel(old_level)
+
+        if handler.records:
+            level_name = logging.getLevelName(level)
+            n_logs = len(handler.records)
+            base_message = f"{n_logs} logs of {level_name} or higher were triggered on {logger.name}:\n"
+            records = [str(record) for record in handler.records]
+            record_message = "\n".join(records)
+            standard_message = self._truncateMessage(base_message, record_message)
+            msg = self._formatMessage(msg, standard_message)
+            self.fail(msg)