tests: use CONTAINER_PROFILE and surface runqemu errors in lxc fixture

Two correctness improvements to the lxc runtime test fixture.

  1. Switch the build from CONTAINER_IMAGE_HOST_EXTRA_INSTALL = "lxc"
     to CONTAINER_PROFILE = "lxc".

     The original fixture set CONTAINER_IMAGE_HOST_EXTRA_INSTALL to
     force lxc into the rootfs without depending on a profile fragment,
     because at the time no lxc profile existed. Now that
     container-host-lxc.conf is in tree, the test should exercise the
     same path real users take — which is the entire point of a
     runtime test. Using the profile also pulls in lxc-networking and
     lxc-templates automatically (via packagegroup-lxc), where the
     original "just install lxc" approach silently left a half-broken
     LXC the test couldn't usefully verify.

  2. Capture the runqemu output to a file and surface it in the
     pexpect.EOF failure message.

     pexpect's default 100-character "before" buffer truncates
     runqemu's actual error to the trailing fragment, which is rarely
     enough to diagnose the failure. Boot failures during fixture
     setup now print the last 60 lines of the runqemu log into the
     pytest failure message and leave the full log at
     /tmp/test_lxc_runtime-runqemu.log for follow-up. When the lxc
     image still wasn't booting cleanly, this is what made the
     "lxc-net.service could not be found" / bridge-missing root cause
     visible without re-instrumenting the fixture.

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>

1 files changed, 29 insertions, 9 deletions

diff --git a/tests/test_lxc_runtime.py b/tests/test_lxc_runtime.py
index 695cfeb7..d3a55188 100644
--- a/tests/test_lxc_runtime.py
+++ b/tests/test_lxc_runtime.py
@@ -6,8 +6,9 @@ LXC runtime tests — boot container-image-host with lxc installed and
 exercise the LXC command-line lifecycle (create, start, attach, stop,
 destroy).
 
-The tests build container-image-host with CONTAINER_IMAGE_HOST_EXTRA_INSTALL
-including lxc. No local.conf changes needed.
+The tests build container-image-host with CONTAINER_PROFILE=lxc, which
+pulls in packagegroup-lxc (lxc + lxc-networking + lxc-templates). No
+local.conf changes needed.
 
 The download-template regression check (TestLxcDownloadTemplate) exists
 specifically to catch the class of bug reported on the meta-virt list
@@ -87,11 +88,13 @@ def _run_bitbake(build_dir, recipe, extra_vars=None, timeout=3600):
 
 @pytest.fixture(scope="module")
 def lxc_image(request):
-    """Build container-image-host with lxc included.
+    """Build container-image-host with the lxc container profile.
 
-    Uses CONTAINER_IMAGE_HOST_EXTRA_INSTALL to add the lxc package without
-    needing to touch local.conf or invent a dedicated container-host-lxc
-    profile fragment.
+    CONTAINER_PROFILE=lxc resolves via conf/distro/include/meta-virt-container-lxc.inc
+    to VIRTUAL-RUNTIME_container_engine=lxc, which container-image-host.bb
+    treats as a signal to install packagegroup-lxc (lxc + lxc-networking
+    + lxc-templates). Same mechanism the incus / podman / k3s profiles
+    use, so the test exercises the same code path real users would take.
     """
     poky_dir = Path(request.config.getoption("--poky-dir"))
     bd = request.config.getoption("--build-dir")
@@ -99,7 +102,7 @@ def lxc_image(request):
     result = _run_bitbake(
         build_dir, "container-image-host",
         extra_vars={
-            "CONTAINER_IMAGE_HOST_EXTRA_INSTALL": "lxc",
+            "CONTAINER_PROFILE": "lxc",
         },
     )
     if result.returncode != 0:
@@ -123,13 +126,30 @@ def lxc_qemu(request, lxc_image):
         f"{kvm_opt} qemuparams=\"-m 4096\""
     )
 
+    # Route runqemu's full output to /tmp so a boot failure leaves a
+    # diagnosable trail. pexpect's default 100-char-truncated "before"
+    # buffer hides the actual error from pytest's traceback otherwise.
+    log_path = Path(tempfile.gettempdir()) / "test_lxc_runtime-runqemu.log"
+    log_path.write_text("")  # truncate from any prior run
+    log_fp = log_path.open("w")
     child = pexpect.spawn(
         f"bash -c 'cd {poky_dir} && source oe-init-build-env {builddir} "
         f">/dev/null 2>&1 && {cmd}'",
-        timeout=boot_timeout, encoding="utf-8", logfile=None,
+        timeout=boot_timeout, encoding="utf-8", logfile=log_fp,
     )
 
-    child.expect(r"login:", timeout=boot_timeout)
+    try:
+        child.expect(r"login:", timeout=boot_timeout)
+    except pexpect.EOF:
+        log_fp.flush()
+        log_fp.close()
+        # Drop the last 60 lines of the runqemu log into the failure
+        # message so the actual cause is visible without grepping.
+        tail = "\n".join(log_path.read_text().splitlines()[-60:])
+        pytest.fail(
+            f"runqemu exited before login prompt. Full log at {log_path}.\n"
+            f"Tail:\n{tail}"
+        )
     child.sendline("root")
     child.expect(r"root@.*[:~#]", timeout=30)