fix(ci): the durations refresh keeps the times of a tier the run skipped

.github/scripts/slow_test_durations.py

@@ -4,9 +4,9 @@
     python .github/scripts/slow_test_durations.py junit-*/junit-*.xml
 
 Use a green ``main`` run: it has a ``junit-*`` artifact for every shard of the slow tier, the gateway tests, the unit
-tier and the installer tier, which ``gh run download`` puts in a folder each. Pass them all, since the table is
-rewritten whole. Each test's time counts toward its file, or toward the test itself for a file the table names in
-``split_by_test``; that list is kept as it is.
+tier and the installer tier, which ``gh run download`` puts in a folder each. Each test's time counts toward its file,
+or toward the test itself for a file the table names in ``split_by_test``; that list is kept as it is. A file the
+reports have no test of, such as one of a tier the run skipped, keeps the times the table had for it while it exists.
 """
 
 from __future__ import annotations
@@ -43,9 +43,13 @@ def main() -> int:
     if not seconds:
         print("slow test durations: the reports have no test cases; the table is unchanged")
         return 1
-    table["seconds"] = {unit: round(value, 1) for unit, value in sorted(seconds.items())}
+    reported = {unit.split("::", 1)[0] for unit in seconds}
+    kept = {unit: value for unit, value in table.get("seconds", {}).items()
+            if unit.split("::", 1)[0] not in reported and (args.root / unit.split("::", 1)[0]).is_file()}
+    table["seconds"] = {unit: round(value, 1) for unit, value in sorted({**kept, **seconds}.items())}
     args.table.write_text(json.dumps(table, indent=1) + "\n")
-    print(f"slow test durations: {len(seconds)} units, {sum(seconds.values()) / 60:.1f} min, written to {args.table}")
+    print(f"slow test durations: {len(seconds)} units, {sum(seconds.values()) / 60:.1f} min, and {len(kept)} kept "
+          f"from files the reports have no test of, written to {args.table}")
     return 0
 
 

tst/unit/test_slow_test_durations_script.py

@@ -67,3 +67,29 @@ def test_reports_with_no_cases_leave_the_table_as_it_was(tmp_path):
     result = _refresh(table, tmp_path, _report(tmp_path, "empty.xml", []))
     assert result.returncode == 1
     assert table.read_text() == before
+
+
+def test_a_file_the_reports_have_no_test_of_keeps_its_times(tmp_path):
+    table = _checkout(tmp_path)
+    installer = "tst/installer/plugin_add_test.py"
+    (tmp_path / installer).parent.mkdir(parents=True)
+    (tmp_path / installer).write_text("")
+    table.write_text(json.dumps({"split_by_test": [SPLIT], "seconds": {
+        installer: 120.0, f"{SPLIT}::test_old": 50.0, "tst/integration/cli/cli_test.py": 80.0,
+        "tst/integration/gone_test.py": 9}}))
+    report = _report(tmp_path, "r.xml", [("tst.integration.cli.cli_test", "test_deploy", 5.0)])
+    result = _refresh(table, tmp_path, report)
+    assert result.returncode == 0, result.stdout
+    assert json.loads(table.read_text())["seconds"] == {
+        "tst/installer/plugin_add_test.py": 120.0,
+        "tst/integration/cli/cli_test.py": 5.0,
+        f"{SPLIT}::test_old": 50.0,
+    }
+
+
+def test_a_reported_split_file_drops_its_tests_the_reports_dont_have(tmp_path):
+    table = _checkout(tmp_path)
+    table.write_text(json.dumps({"split_by_test": [SPLIT], "seconds": {f"{SPLIT}::test_renamed": 50.0}}))
+    report = _report(tmp_path, "r.xml", [("tst.integration.env.gateway.gateway_test", "test_new", 7.0)])
+    assert _refresh(table, tmp_path, report).returncode == 0
+    assert json.loads(table.read_text())["seconds"] == {f"{SPLIT}::test_new": 7.0}