Add post-mortem information collection for failed tests

In some situations, when examine failed tests it would be helpful to
collect some extra information on the system state.

This changeset adds a fixture that triggers data collection.
A fixture, contrary to a hook, allows to re-use existing
fixtures (e.g. the `strategy`-fixture).
Using `autouse=True` this fixture is injected into every test.

To make the test result available in fixtures a hook in
`pytest_runtest_makereport` is used.

The actual diagnosis data is collected inside the strategy.
This way the infrastructure is re-useable and knowledge on the system
state stays inside the strategy.

In case of a test failure this generates log output that may look like
this:

---- 8< ----

========== FAILURES ==========
____ test_tacd_uart_3v3 ______

(...)
    @pytest.mark.lg_feature("eet")
    def test_tacd_uart_3v3(strategy, shell, eet, record_property):
(...)
>       assert True == False
E       assert True == False

tests/test_tacd.py:248: AssertionError

---- Captured log teardown -----
(...)
WARNING     post-mortem:  POST-MORTEM INFO: status
WARNING     post-mortem:  | shell
WARNING     post-mortem:  POST-MORTEM INFO: uname -a
WARNING     post-mortem:  | Linux lxatac-00034 6.17.0-20251007-1 #1 SMP PREEMPT Sun Sep 28 21:39:22 UTC 2025 armv7l GNU/Linux
WARNING     post-mortem:  POST-MORTEM INFO: cat /etc/os-release
WARNING     post-mortem:  | ID=tacos
WARNING     post-mortem:  | NAME="TAC OS - The LXA TAC operating system"
WARNING     post-mortem:  | VERSION="25.09+dev (tacos-walnascar)"
WARNING     post-mortem:  | VERSION_ID=25.09-dev
WARNING     post-mortem:  | VERSION_CODENAME="tacos-walnascar"
WARNING     post-mortem:  | PRETTY_NAME="TAC OS - The LXA TAC operating system 25.09+dev (tacos-walnascar)"
WARNING     post-mortem:  | CPE_NAME="cpe:/o:openembedded:tacos:25.09+dev"
WARNING     post-mortem:  POST-MORTEM INFO: cat /etc/buildinfo
WARNING     post-mortem:  | -----------------------
WARNING     post-mortem:  | Build Configuration:  |
WARNING     post-mortem:  | -----------------------
WARNING     post-mortem:  | DISTRO = tacos
WARNING     post-mortem:  | DISTRO_VERSION = 25.09+dev
WARNING     post-mortem:  | -----------------------
WARNING     post-mortem:  | Layer Revisions:      |
WARNING     post-mortem:  | -----------------------
WARNING     post-mortem:  | meta              = HEAD:d0b46a6624ec9c61c47270745dd0b2d5abbe6ac1
WARNING     post-mortem:  | meta-poky         = HEAD:d0b46a6624ec9c61c47270745dd0b2d5abbe6ac1
WARNING     post-mortem:  | meta-arm          = HEAD:21894cc2ea3197e6bfc1a56d889f757a09dc8b31
WARNING     post-mortem:  | meta-arm-toolchain = HEAD:21894cc2ea3197e6bfc1a56d889f757a09dc8b31
WARNING     post-mortem:  | meta-ptx          = HEAD:23e46e92946ca0a1b1da4cf3ad212169d46b0af8
WARNING     post-mortem:  | meta-oe           = HEAD:80ab58cc404959ae2f0e8b2e68935b3bfd8e8cfe
WARNING     post-mortem:  | meta-python       = HEAD:80ab58cc404959ae2f0e8b2e68935b3bfd8e8cfe
WARNING     post-mortem:  | meta-filesystems  = HEAD:80ab58cc404959ae2f0e8b2e68935b3bfd8e8cfe
WARNING     post-mortem:  | meta-networking   = HEAD:80ab58cc404959ae2f0e8b2e68935b3bfd8e8cfe
WARNING     post-mortem:  | meta-lxatac-bsp   = HEAD:44e447b099a268f87a305915a386568e0ff72b6a
WARNING     post-mortem:  | meta-lxatac-software = HEAD:44e447b099a268f87a305915a386568e0ff72b6a
WARNING     post-mortem:  | meta-labgrid      = HEAD:fa2c78d1fc3ff9519ddd14168807519ec0b6d9ee
WARNING     post-mortem:  | meta-rauc         = HEAD:a0b83842d131093e89fa4fefaaa1997f05afdf62
WARNING     post-mortem:  | meta-virtualization = HEAD:4fedb61ebf60745a367d857af255006bd3509a39
WARNING     post-mortem:  | meta-selinux      = HEAD:7ba3272c1f23266a1822442d640a40b6b4feff8c
(...)

---- 8< ----

Signed-off-by: Chris Fiege <[email protected]>

Author: SmithChart

conftest.py

@@ -5,6 +5,8 @@
 
 import pytest
 
+pytest_plugins = ["postmortem"]
+
 
 @pytest.fixture(scope="function")
 def barebox(strategy):

lxatacstrategy.py

@@ -204,3 +204,31 @@ def activate_optionals(self):
         if self.ethmux:
             self.target.activate(self.ethmux)
             self.ethmux.set(True)  # Connect upstream Ethernet to Lab network as default
+
+    def postmortem_info(self) -> dict[str, list[str]]:
+        pm_info: dict[str, list[str]] = {"status": [self.status.name]}
+
+        def get_info(shell, command):
+            pm_info[command] = shell.run_check(command)
+
+        if self.status == Status.barebox:
+            get_info(self.barebox, "version")
+            get_info(self.barebox, "mount")
+            get_info(self.barebox, "global")
+            get_info(self.barebox, "nv")
+            get_info(self.barebox, "dmesg")
+        elif self.status == Status.shell:
+            get_info(self.shell, "uname -a")
+            get_info(self.shell, "cat /etc/os-release")
+            get_info(self.shell, "cat /etc/buildinfo")
+            get_info(self.shell, "dmesg -l 5")
+            get_info(self.shell, "findmnt")
+            get_info(self.shell, "lsns")
+            get_info(self.shell, "ip -brief address")
+            get_info(self.shell, "ip -brief route")
+            get_info(self.shell, "ip -brief -6 route")
+            get_info(self.shell, "df --human-readable")
+            get_info(self.shell, "free -m")
+            get_info(self.shell, "systemctl list-units --failed")
+
+        return pm_info

postmortem.py

@@ -0,0 +1,49 @@
+import logging
+
+import pytest
+from pytest import CollectReport, StashKey
+
+_phase_report_key = StashKey[dict[str, CollectReport]]()
+_pm_logger = logging.getLogger("post-mortem")
+
+
+@pytest.hookimpl(wrapper=True, tryfirst=True)
+def pytest_runtest_makereport(item: pytest.Item, call: pytest.CallInfo[None]):
+    """
+    Make the report for a step available in the item's stash, so that
+    fixtures can read the result in their teardown phase.
+    Heavily inspired by: https://docs.pytest.org/en/latest/example/simple.html#making-test-result-information-available-in-fixtures
+    Implements the runtest_makereport-hook: https://docs.pytest.org/en/latest/reference/reference.html#std-hook-pytest_runtest_makereport
+
+    :param item: The item the report is generated for.
+    :param call: CallInfo for this phase
+    :return: The report re received from the previous hook.
+    """
+    rep = yield
+
+    # store test results for each phase of a call, which can
+    # be "setup", "call", "teardown"
+    item.stash.setdefault(_phase_report_key, {})[rep.when] = rep
+    return rep
+
+
+@pytest.fixture(autouse=True)
+def pm_system(request: pytest.FixtureRequest, strategy, record_property):
+    """
+    Retrieves post-mortem diagnosis information from the strategy and emits the information to the log with level
+    WARNING and also adds the information to the `junit.xml`.
+
+    The strategy must implement a strategy.postmotem_info().
+    It is up to the strategy to decide which information to collect depending on the DUTs status and the connections
+    available (e.g. serial or ssh).
+    """
+    yield
+
+    report = request.node.stash[_phase_report_key]
+    if "call" in report and report["call"].failed:
+        post_mortem_info: dict[str, list[str]] = strategy.postmortem_info()
+        record_property("postmortem", post_mortem_info)
+        for key, value in post_mortem_info.items():
+            _pm_logger.warning(f"POST-MORTEM INFO: {key}")
+            for line in value:
+                _pm_logger.warning(f"| {line}")