test(ci): cover the mesh axis

A fully pinned priority row now pins the mesh state too, and a priority row
with more combinations than the distro pool has members wraps the rotation
instead of holding one distribution per combination.

tests/unit/python/utils/github/variant/test_axes.py

@@ -111,6 +111,7 @@ class TestArtifactSlug(unittest.TestCase):
                             entry["tor"] == "true",
                             entry["distro"],
                             entry["filesystem"],
+                            entry["vpn"] == "true",
                         ),
                     ),
                 )
@@ -222,7 +223,7 @@ class TestPriorityCoverage(unittest.TestCase):
     def test_an_incapable_priority_variant_skips_its_onion_runs(self) -> None:
         rows = [_row("web-app-a", 1, ("compose", "swarm"), priority=True)]
         entries = _assign(rows, sweep=0, tor_mode="auto", variants_per_app=_VARIANTS)
-        self.assertEqual([e["tor"] for e in entries], ["false", "false"])
+        self.assertEqual({e["tor"] for e in entries}, {"false"})
 
 
 class TestAssign(unittest.TestCase):
@@ -371,6 +372,7 @@ class TestPinnedAxes(unittest.TestCase):
             priority=True,
             pin_mode="swarm",
             pin_tor=False,
+            pin_vpn=False,
         )
         self.assertEqual(len(self._entries(row)), 1)
 
@@ -447,7 +449,13 @@ class TestDistroAndFilesystemAxes(unittest.TestCase):
     def test_a_priority_row_spreads_its_combinations_over_the_pool(self) -> None:
         rows = [_row("web-app-b", 0, ("compose", "swarm"), priority=True)]
         entries = _assign(rows, sweep=0, tor_mode="auto", variants_per_app=_VARIANTS)
-        self.assertEqual(len({e["distro"] for e in entries}), len(entries))
+        self.assertEqual(
+            len({e["distro"] for e in entries}),
+            min(len(entries), len(axes.DISTROS)),
+            "a priority row must walk the pool, not repeat one distribution; "
+            "once it has more combinations than the pool has members, the "
+            "rotation wraps and every distribution is proven at least once",
+        )
 
     def test_a_pinned_distro_replaces_the_rotation(self) -> None:
         rows = [_row("web-app-b", 0, ("compose",), pin_distro="fedora")]