US07-04: Prove Concurrency and Crash Recovery (#86)

tests/conftest.py

@@ -1,5 +1,6 @@
-"""Make the repository root importable for the pipeline test suites, and give every
-suite the application session the API requires since US07-02.
+"""Make the repository root importable for the pipeline test suites, give every
+suite the application session the API requires since US07-02, and keep the evidence
+of any failure (US07-04).
 
 The suites drive the API the way the browser does — module-level ``httpx`` calls and
 ``TestClient`` — so instead of threading a cookie through several hundred call sites,
@@ -99,3 +100,30 @@ def _api_session():
     httpx._api.request, httpx.request = real_request, real_request
     httpx._api.stream, httpx.stream = real_stream, real_stream
     TestClient.request, TestClient.__init__ = real_client_request, real_client_init
+
+
+@pytest.hookimpl(hookwrapper=True)
+def pytest_runtest_makereport(item, call):
+    """On failure, keep the temporary library, database, journals, logs, and seed.
+
+    ``tmp_path`` is deleted a few runs later and its contents are the only record
+    of what a randomized or fault-injected failure actually did, so they are copied
+    out while they still exist (US07-04).
+    """
+    outcome = yield
+    report = outcome.get_result()
+    if report.when != "call" or not report.failed:
+        return
+    root = item.funcargs.get("tmp_path")
+    if root is None or not Path(root).exists():
+        return
+    from tests._artifacts import collect
+
+    try:
+        destination = collect(
+            Path(root), item.nodeid, properties=dict(getattr(report, "user_properties", []))
+        )
+    except OSError as error:  # never let evidence collection mask the real failure
+        report.sections.append(("failure artifacts", f"could not be collected: {error}"))
+    else:
+        report.sections.append(("failure artifacts", str(destination)))