tests: add unit and functional tests for distro module

Add comprehensive test coverage for the distro module:

- 24 new unit tests covering LinuxDistro, Probe methods, regex patterns,
  SUSEProbe custom logic, register_probe, detect scoring/fallback, Spec
- 1 new functional test for local system detection
- Update TEST_SIZE counts in check.py (unit: 976->1000, functional: 368->369)

Coverage: 95% (untested: remote SSH session paths)

Assisted-By: Cursor-Claude-4-Sonnet
Signed-off-by: Harvey Lynden <hlynden@redhat.com>

Author: harvey0100

selftests/check.py

@@ -27,9 +27,9 @@
     "job-api-check-tmp-directory-exists": 1,
     "nrunner-interface": 90,
     "nrunner-requirement": 28,
-    "unit": 976,
+    "unit": 1000,
     "jobs": 11,
-    "functional-parallel": 368,
+    "functional-parallel": 369,
     "functional-serial": 7,
     "optional-plugins": 0,
     "optional-plugins-golang": 2,

selftests/functional/utils/distro.py

@@ -1,10 +1,12 @@
 import os
+import platform
 
 from avocado import Test
 from avocado.core.exit_codes import AVOCADO_ALL_OK
 from avocado.core.job import Job
 from avocado.core.nrunner.runnable import Runnable
 from avocado.core.suite import TestSuite
+from avocado.utils import distro
 
 
 class Distro(Test):
@@ -64,3 +66,28 @@ def test_debian_12_7(self):
             + os.uname().machine.encode()
             + b") version 12 release 7\n",
         )
+
+
+class DistroDetectLocal(Test):
+    """Tests distro detection on the local system without containers."""
+
+    def test_detect_current_system(self):
+        """Verify detect() returns a valid result for the running system."""
+        result = distro.detect()
+        self.assertIsInstance(result, distro.LinuxDistro)
+        has_release_file = any(
+            os.path.exists(p)
+            for p in [
+                "/etc/os-release",
+                "/etc/redhat-release",
+                "/etc/fedora-release",
+                "/etc/debian_version",
+            ]
+        )
+        if has_release_file:
+            self.assertNotEqual(
+                result.name,
+                distro.UNKNOWN_DISTRO_NAME,
+                "detect() should identify a known distro on this system",
+            )
+            self.assertEqual(result.arch, platform.machine())