CB-554: weight <= 0 excludes a profile from automatic placement, not 1.0

bridged/src/test/java/dev/ltms/bridged/placement/PlacementPolicyTest.java

@@ -237,6 +237,105 @@ class PlacementPolicyTest {
         assertTrue(e.getMessage().contains("1 unreachable"), e.getMessage());
     }
 
+    // --- CB-554: weight <= 0 excludes a candidate from automatic selection ------------------
+
+    @Test
+    void weightedSkipsWeightZeroProfile() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 0.0f, null),
+                PlacementCandidate.profile("b", 1.0f, null));
+        for (int i = 0; i < 5; i++) {
+            assertEquals("b", policy.select(ctx(candidates, noSessions())).profile(),
+                    "a has weight 0, so every pick lands on b");
+        }
+    }
+
+    @Test
+    void weightedThrowsWhenAllWeightZero() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 0.0f, null),
+                PlacementCandidate.profile("b", 0.0f, null));
+        PlacementException e = assertThrows(PlacementException.class,
+                () -> policy.select(ctx(candidates, noSessions())));
+        assertTrue(e.getMessage().contains("weight 0"), e.getMessage());
+    }
+
+    @Test
+    void weightedTreatsNegativeWeightAsExcludedNotError() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", -1.0f, null),
+                PlacementCandidate.profile("b", 1.0f, null));
+        for (int i = 0; i < 5; i++) {
+            assertEquals("b", policy.select(ctx(candidates, noSessions())).profile(),
+                    "a has a negative weight, so it is excluded like weight 0 — never picked, never an error");
+        }
+    }
+
+    @Test
+    void weightZeroAndQuarantinedIsNotDoubleCounted() {
+        PlacementPolicy policy = PlacementPolicies.weighted();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 0.0f, null),
+                PlacementCandidate.profile("b", 1.0f, null),
+                PlacementCandidate.profile("c", 1.0f, null));
+        // a is BOTH weight-0 and quarantined; b and c are quarantined only. If a were counted
+        // into both buckets, "quarantined" would read 3 (or the arithmetic would go negative)
+        // instead of the true count of 2 candidates actually quarantined.
+        PlacementContext mixedCtx = ctx(candidates, noSessions(), Set.of(), Set.of("a", "b", "c"));
+        PlacementException e = assertThrows(PlacementException.class, () -> policy.select(mixedCtx));
+        assertTrue(e.getMessage().contains("1 weight-0"), e.getMessage());
+        assertTrue(e.getMessage().contains("2 quarantined"), e.getMessage());
+        assertTrue(e.getMessage().contains("0 remaining"), e.getMessage());
+    }
+
+    @Test
+    void roundRobinSkipsWeightZeroProfiles() {
+        PlacementPolicy policy = PlacementPolicies.roundRobin();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 0.0f, null),
+                PlacementCandidate.profile("b", 1.0f, null));
+        for (int i = 0; i < 5; i++) {
+            assertEquals("b", policy.select(ctx(candidates, noSessions())).profile(),
+                    "a has weight 0, so every pick lands on b");
+        }
+    }
+
+    @Test
+    void roundRobinThrowsWhenAllWeightZero() {
+        PlacementPolicy policy = PlacementPolicies.roundRobin();
+        List<PlacementCandidate> candidates = List.of(
+                PlacementCandidate.profile("a", 0.0f, null),
+                PlacementCandidate.profile("b", 0.0f, null));
+        PlacementException e = assertThrows(PlacementException.class,
+                () -> policy.select(ctx(candidates, noSessions())));
+        assertTrue(e.getMessage().contains("weight 0"), e.getMessage());
+    }
+
+    @Test
+    void fixedSkipsWeightZeroDefault() {
+        PlacementPolicy policy = PlacementPolicies.fixed();
+        PlacementContext ctx = new PlacementContext("b",
+                List.of(PlacementCandidate.profile("a", 1.0f, null),
+                        PlacementCandidate.profile("b", 0.0f, null)),
+                noSessions(), Set.of(), Set.of());
+        assertEquals("a", policy.select(ctx).profile(),
+                "the default 'b' has weight 0, so fixed falls through to the first available candidate");
+    }
+
+    @Test
+    void fixedThrowsWhenDefaultAndEveryCandidateWeightZero() {
+        PlacementPolicy policy = PlacementPolicies.fixed();
+        PlacementContext ctx = new PlacementContext("b",
+                List.of(PlacementCandidate.profile("a", 0.0f, null),
+                        PlacementCandidate.profile("b", 0.0f, null)),
+                noSessions(), Set.of(), Set.of());
+        PlacementException e = assertThrows(PlacementException.class, () -> policy.select(ctx));
+        assertTrue(e.getMessage().contains("weight 0"), e.getMessage());
+    }
+
     @Test
     void unknownPolicyNameThrows() {
         assertThrows(IllegalArgumentException.class, () -> PlacementPolicies.fromName("random"));