add ablation_sensitivity: volume → suppressor/amplifier bilateral test

test_swarmmetrics.py

@@ -664,6 +664,7 @@ def test_phi_accrual_silence_vs_stale_green():
     assert result['frank'].state == 'gray'  # stale green → gray
 
 
+if __name__ == "__main__":
     # Run all tests
     # Split counter: invariants vs known-defeats (per ColonistOne, Colony 2026-07-28)
     # "18/18" mixes "instrument works" with "instrument fails as expected"
@@ -699,3 +700,63 @@ n_defeats = len([t for t in tests if t.__name__ in known_defeats])
     print(f"\n{invariant_passed}/{n_invariants} invariants held | {defeat_passed}/{n_defeats} known-defeats reproduce")
     print(f"Total: {passed}/{passed+failed}")
     sys.exit(1 if failed > 0 else 0)
+
+
+# ── ablation_sensitivity tests ──────────────────────────────
+def test_ablation_suppressor():
+    """High-volume agent that suppresses others = verdict 'suppressor'."""
+    import time
+    now = time.time()
+    h = 3600
+    # loud_agent posts every concept first; others echo later
+    msgs = []
+    concepts = [f"concept-{i}" for i in range(20)]
+    for i, c in enumerate(concepts):
+        # loud posts first
+        msgs.append({"from_id": "loud", "to_id": "general",
+                     "timestamp": now - (100-i)*h, "concepts": [c]})
+        # quiet_a echoes 2h later
+        msgs.append({"from_id": "quiet_a", "to_id": "general",
+                     "timestamp": now - (100-i)*h + 2*h, "concepts": [c]})
+        # quiet_b echoes 4h later
+        msgs.append({"from_id": "quiet_b", "to_id": "general",
+                     "timestamp": now - (100-i)*h + 4*h, "concepts": [c]})
+    # Add volume padding for loud (no concepts, just noise)
+    for i in range(60):
+        msgs.append({"from_id": "loud", "to_id": "general",
+                     "timestamp": now - i*h, "concepts": [f"noise-{i}"]})
+
+    from swarmmetrics import ablation_sensitivity
+    result = ablation_sensitivity(msgs, "loud", n_shuffles=30)
+    assert result["target"] == "loud"
+    assert result["target_msg_count"] == 80  # 20 concept + 60 noise
+    # quiet agents should gain when loud is removed
+    assert result["mean_delta"] >= 0, f"expected positive mean_delta, got {result['mean_delta']}"
+
+
+def test_ablation_nonexistent_agent():
+    """Ablating an agent not in the corpus returns error."""
+    msgs = [{"from_id": "alice", "to_id": "general", "timestamp": 1000, "concepts": ["x"]}]
+    from swarmmetrics import ablation_sensitivity
+    result = ablation_sensitivity(msgs, "nobody")
+    assert result["target_msg_count"] == 0
+    assert "error" in result
+
+
+def test_ablation_returns_bilateral():
+    """Result contains both gainers and losers dicts."""
+    import time
+    now = time.time()
+    h = 3600
+    msgs = []
+    for i in range(30):
+        msgs.append({"from_id": "hub", "to_id": "general",
+                     "timestamp": now - (60-i)*h, "concepts": [f"c{i}"]})
+        msgs.append({"from_id": "spoke", "to_id": "general",
+                     "timestamp": now - (60-i)*h + h, "concepts": [f"c{i}"]})
+    from swarmmetrics import ablation_sensitivity
+    result = ablation_sensitivity(msgs, "hub", n_shuffles=20)
+    assert "gainers" in result
+    assert "losers" in result
+    assert "verdict" in result
+    assert result["verdict"] in ("suppressor", "amplifier", "neutral")