pytest: Pass result to fixtures and keep directories of failed tests

@Reported-by: Rusty Russell <@rustyrussell>
@Signed-off-by: Christian Decker <@cdecker>

tests/conftest.py

@@ -0,0 +1,18 @@
+import pytest
+
+
+# This function is based upon the example of how to
+# "[make] test result information available in fixtures" at:
+#  https://pytest.org/latest/example/simple.html#making-test-result-information-available-in-fixtures
+# and:
+#  https://github.com/pytest-dev/pytest/issues/288
+@pytest.hookimpl(tryfirst=True, hookwrapper=True)
+def pytest_runtest_makereport(item, call):
+    # execute all other hooks to obtain the report object
+    outcome = yield
+    rep = outcome.get_result()
+
+    # set a report attribute for each phase of a call, which can
+    # be "setup", "call", "teardown"
+
+    setattr(item, "rep_" + rep.when, rep)

tests/fixtures.py

@@ -35,7 +35,7 @@ def test_base_dir():
 
 
 @pytest.fixture
-def directory(test_base_dir, test_name):
+def directory(request, test_base_dir, test_name):
     """Return a per-test specific directory.
 
     This makes a unique test-directory even if a test is rerun multiple times.
@@ -48,7 +48,12 @@ def directory(test_base_dir, test_name):
 
     yield directory
 
-    shutil.rmtree(directory)
+    # This uses the status set in conftest.pytest_runtest_makereport to
+    # determine whether we succeeded or failed.
+    if request.node.rep_call.outcome == 'passed':
+        shutil.rmtree(directory)
+    else:
+        logging.debug("Test execution failed, leaving the test directory {} intact.".format(directory))
 
 
 @pytest.fixture