[ci] Extract integration test bucketing into a pure function

Pull the run_all glob expansion + bucket computation out of main() into
_compute_integration_test_buckets() returning (run_integration, buckets).
The boundary tests now call this helper directly instead of driving
main() through ~14 patched dependencies, which both shrinks the test
helper and removes duplication with the existing test_main_* fixtures.

tests/script/test_determine_jobs.py

@@ -1,9 +1,7 @@
 """Unit tests for script/determine-jobs.py module."""
 
 from collections.abc import Generator
-import contextlib
 import importlib.util
-import io
 import json
 import os
 from pathlib import Path
@@ -382,106 +380,41 @@ def test_main_with_branch_argument(
     assert output["cpp_unit_tests_components"] == ["mqtt"]
 
 
-def _run_main_for_integration_buckets(
-    *,
-    integration_return: tuple[bool, list[str]],
-    glob_files: list[str] | None = None,
-) -> dict:
-    """Drive determine_jobs.main() with stubbed inputs and return its parsed output.
-
-    Helper for testing integration_test_buckets in isolation. Bypasses every
-    unrelated branch (clang-tidy, components, memory, cpp tests, batches) so
-    the test focuses purely on the bucketing decision logic.
-    """
-    patches: list = [
-        patch.object(
-            determine_jobs,
-            "determine_integration_tests",
-            return_value=integration_return,
-        ),
-        patch.object(determine_jobs, "should_run_clang_tidy", return_value=False),
-        patch.object(determine_jobs, "should_run_clang_format", return_value=False),
-        patch.object(determine_jobs, "should_run_python_linters", return_value=False),
-        patch.object(determine_jobs, "should_run_import_time", return_value=False),
-        patch.object(determine_jobs, "count_changed_cpp_files", return_value=0),
-        patch.object(determine_jobs, "changed_files", return_value=[]),
-        patch.object(determine_jobs, "get_changed_components", return_value=[]),
-        patch.object(
-            determine_jobs, "get_components_with_dependencies", return_value=[]
-        ),
-        patch.object(
-            determine_jobs,
-            "detect_memory_impact_config",
-            return_value={"should_run": "false"},
-        ),
-        patch.object(
-            determine_jobs, "create_intelligent_batches", return_value=([], {})
-        ),
-        patch.object(
-            determine_jobs, "determine_cpp_unit_tests", return_value=(False, [])
-        ),
-        patch.object(determine_jobs, "should_run_benchmarks", return_value=False),
-        patch.object(determine_jobs, "get_target_branch", return_value="dev"),
-        patch("sys.argv", ["determine-jobs.py"]),
-    ]
-    if glob_files is not None:
-        patches.append(
-            patch.object(
-                determine_jobs,
-                "_all_integration_test_files",
-                return_value=glob_files,
-            )
-        )
-
-    buf = io.StringIO()
-    with contextlib.ExitStack() as stack:
-        for p in patches:
-            stack.enter_context(p)
-        with contextlib.redirect_stdout(buf):
-            determine_jobs.main()
-    return json.loads(buf.getvalue())
+def test_compute_integration_test_buckets_empty() -> None:
+    """No integration tests scheduled => (False, [])."""
+    run, buckets = determine_jobs._compute_integration_test_buckets(False, [])
+    assert run is False
+    assert buckets == []
 
 
-def test_integration_buckets_empty_when_no_tests() -> None:
-    """No integration tests scheduled => integration_test_buckets is []."""
-    output = _run_main_for_integration_buckets(integration_return=(False, []))
-    assert output["integration_tests"] is False
-    assert output["integration_test_buckets"] == []
+def test_compute_integration_test_buckets_below_threshold() -> None:
+    """A small explicit list (<= threshold) => single 1/1 bucket with that list."""
+    files = [f"tests/integration/test_{name}.py" for name in ("c", "a", "b")]
+    run, buckets = determine_jobs._compute_integration_test_buckets(False, files)
+    assert run is True
+    assert buckets == [{"name": "1/1", "tests": sorted(files)}]
 
 
-def test_integration_buckets_specific_files_below_threshold() -> None:
-    """A small explicit list (<= threshold) produces a single 1/1 bucket
-    containing exactly that list as a JSON array."""
-    files = [f"tests/integration/test_{name}.py" for name in ("a", "b", "c", "d", "e")]
-    output = _run_main_for_integration_buckets(integration_return=(False, files))
-    assert output["integration_tests"] is True
-    buckets = output["integration_test_buckets"]
-    assert len(buckets) == 1
-    assert buckets[0]["name"] == "1/1"
-    assert buckets[0]["tests"] == sorted(files)
-
-
-def test_integration_buckets_at_threshold_stays_single() -> None:
-    """Exactly INTEGRATION_TESTS_SPLIT_THRESHOLD files stays as one bucket
+def test_compute_integration_test_buckets_at_threshold_stays_single() -> None:
+    """Exactly INTEGRATION_TESTS_SPLIT_THRESHOLD files => still one bucket
     (the split kicks in only when count is strictly greater than threshold)."""
     files = [
         f"tests/integration/test_{i:02d}.py"
         for i in range(determine_jobs.INTEGRATION_TESTS_SPLIT_THRESHOLD)
     ]
-    output = _run_main_for_integration_buckets(integration_return=(False, files))
-    buckets = output["integration_test_buckets"]
+    run, buckets = determine_jobs._compute_integration_test_buckets(False, files)
+    assert run is True
     assert len(buckets) == 1
     assert buckets[0]["name"] == "1/1"
     assert buckets[0]["tests"] == sorted(files)
 
 
-def test_integration_buckets_just_over_threshold_splits() -> None:
-    """One file over the threshold triggers the 3-bucket fan-out."""
+def test_compute_integration_test_buckets_just_over_threshold_splits() -> None:
+    """One file over the threshold triggers the 3-bucket fan-out, balanced."""
     n = determine_jobs.INTEGRATION_TESTS_SPLIT_THRESHOLD + 1
     files = [f"tests/integration/test_{i:02d}.py" for i in range(n)]
-    output = _run_main_for_integration_buckets(integration_return=(False, files))
-    buckets = output["integration_test_buckets"]
-    assert len(buckets) == determine_jobs.INTEGRATION_TESTS_SPLIT_BUCKETS
+    run, buckets = determine_jobs._compute_integration_test_buckets(False, files)
+    assert run is True
     assert [b["name"] for b in buckets] == ["1/3", "2/3", "3/3"]
     union = [path for b in buckets for path in b["tests"]]
     assert union == sorted(files)
@@ -489,15 +422,15 @@ def test_integration_buckets_just_over_threshold_splits() -> None:
     assert max(sizes) - min(sizes) <= 1
 
 
-def test_integration_buckets_run_all_with_empty_glob_disables_run() -> None:
-    """If run_all=True but the glob unexpectedly returns no files, the run is
-    suppressed (otherwise pytest would be invoked with no path argument and
-    collect tests outside tests/integration/)."""
-    output = _run_main_for_integration_buckets(
-        integration_return=(True, []), glob_files=[]
-    )
-    assert output["integration_tests"] is False
-    assert output["integration_test_buckets"] == []
+def test_compute_integration_test_buckets_run_all_with_empty_glob_disables_run() -> (
+    None
+):
+    """run_all=True but glob returns no files => run suppressed (otherwise
+    pytest would collect tests outside tests/integration/)."""
+    with patch.object(determine_jobs, "_all_integration_test_files", return_value=[]):
+        run, buckets = determine_jobs._compute_integration_test_buckets(True, [])
+    assert run is False
+    assert buckets == []
 
 
 def test_determine_integration_tests(