diff --git a/testing/tests/test_publish_test_metrics.py b/testing/tests/test_publish_test_metrics.py
index e0aa8bbb..ff1b9ca7 100644
--- a/testing/tests/test_publish_test_metrics.py
+++ b/testing/tests/test_publish_test_metrics.py
@@ -58,6 +58,18 @@ def test_parse_junit_handles_testsuites_and_invalid_counts(tmp_path: Path):
     }
 
 
+def test_parse_junit_handles_unknown_root(tmp_path: Path):
+    junit_path = tmp_path / "suite.xml"
+    junit_path.write_text("<root><item /></root>", encoding="utf-8")
+
+    assert publish_test_metrics._parse_junit(str(junit_path)) == {
+        "tests": 0,
+        "failures": 0,
+        "errors": 0,
+        "skipped": 0,
+    }
+
+
 def test_read_exit_code_and_summary_fallbacks(tmp_path: Path):
     rc_path = tmp_path / "rc.txt"
     rc_path.write_text("0\n", encoding="utf-8")
@@ -70,6 +82,34 @@ def test_read_exit_code_and_summary_fallbacks(tmp_path: Path):
     assert publish_test_metrics._load_summary(str(tmp_path / "missing.json")) == {}
 
 
+def test_summary_extractors_handle_invalid_shapes_and_values():
+    assert publish_test_metrics._summary_coverage_percent(None) == 0.0
+    assert publish_test_metrics._summary_coverage_percent({"results": "not-a-list"}) == 0.0
+    assert publish_test_metrics._summary_coverage_percent({"results": [42, {"name": "coverage", "status": "failed"}]}) == 0.0
+    assert publish_test_metrics._summary_coverage_percent({"results": [{"name": "coverage", "status": "ok"}]}) == 95.0
+
+    assert publish_test_metrics._summary_source_lines_over_500(None) == 0
+    assert publish_test_metrics._summary_source_lines_over_500({"results": "not-a-list"}) == 0
+    assert publish_test_metrics._summary_source_lines_over_500({"results": [42, {"name": "hygiene", "issues": "bad"}]}) == 0
+    assert (
+        publish_test_metrics._summary_source_lines_over_500(
+            {
+                "results": [
+                    {
+                        "name": "hygiene",
+                        "issues": [
+                            "services/foo.py has 501 lines (max 500)",
+                            "a different issue",
+                            "scripts/bar.sh has 777 lines > 500",
+                        ],
+                    }
+                ]
+            }
+        )
+        == 2
+    )
+
+
 def test_read_text_post_text_and_fetch_existing_counter(monkeypatch):
     class _FakeResponse:
         def __init__(self, payload: str, status: int = 200):
@@ -163,6 +203,26 @@ def test_post_text_raises_and_counter_handles_bad_metric_lines(monkeypatch):
         == 0.0
     )
 
+    monkeypatch.setattr(
+        publish_test_metrics,
+        "_read_text",
+        lambda url: "\n".join(
+            [
+                'different_metric{job="platform-quality-ci",suite="titan-iac",status="ok"} 8',
+                'platform_quality_gate_runs_total{job="platform-quality-ci",suite="other",status="ok"} 8',
+                'platform_quality_gate_runs_total{job="platform-quality-ci",suite="titan-iac",status="ok"} 9',
+            ]
+        ),
+    )
+    assert (
+        publish_test_metrics._fetch_existing_counter(
+            "http://push.invalid",
+            "platform_quality_gate_runs_total",
+            {"job": "platform-quality-ci", "suite": "titan-iac", "status": "ok"},
+        )
+        == 9.0
+    )
+
 
 def test_build_payload_includes_summary_metrics():
     payload = publish_test_metrics._build_payload(