Run unit tests in isolation w/ coverage support.

test/units/conftest.py

@@ -0,0 +1,33 @@
+"""Monkey patch os._exit when running under coverage so we don't lose coverage data in forks, such as with `pytest --boxed`."""
+import gc
+import os
+
+try:
+    import coverage
+except ImportError:
+    coverage = None
+
+
+def pytest_configure():
+    if not coverage:
+        return
+
+    coverage_instances = []
+
+    for obj in gc.get_objects():
+        if isinstance(obj, coverage.Coverage):
+            coverage_instances.append(obj)
+
+    if not coverage_instances:
+        return
+
+    os_exit = os._exit
+
+    def coverage_exit(*args, **kwargs):
+        for instance in coverage_instances:
+            instance.stop()
+            instance.save()
+
+        os_exit(*args, **kwargs)
+
+    os._exit = coverage_exit