test: Use existing golden test for script validation

This commit uses the exiting generated API golden tests (cookiecutter
generate templates) to validate the script works on the current
template.

This ensures that things continue to work even if the template
pyproject.toml file is changed and uses a different format to specify
the grpc/protobuf dependencies.

Signed-off-by: Leandro Lucarella <luca-frequenz@llucax.com>

Author: llucax

tests/cookiecutter/scripts/test_dependabot-grpc-fixer.py

@@ -1,6 +1,10 @@
 """Tests for the dependabot_gprc_fixer package."""
 
 import importlib.util
+import json
+import re
+import shutil
+import sys
 from pathlib import Path
 from typing import Protocol, cast
 
@@ -69,3 +73,174 @@ def test_replace_range_uses_dependency_specific_upper_bounds(
 
     assert count == 1
     assert updated == expected
+
+
+# Integration: run the fixer against pyproject.toml files generated by the
+# cookiecutter template (as captured in tests_golden/). The fixer only applies
+# to API repositories, so we discover every `api*` golden case automatically.
+# This catches drift between the template's runtime range formatting and the
+# regexes in cookiecutter/scripts/dependabot-grpc-fixer.py.
+GOLDEN_API_PYPROJECTS = sorted(
+    (Path(__file__).resolve().parents[3] / "tests_golden").glob(
+        "integration/test_cookiecutter_generation/api*/*/pyproject.toml"
+    )
+)
+
+# Upper-bound offsets the fixer applies per runtime dependency (mirrors
+# `UPPER_BOUND_OFFSETS` in dependabot-grpc-fixer.py). Kept here independently so
+# the test fails loudly if the offsets diverge from the documented contract.
+EXPECTED_UPPER_BOUND_OFFSETS = {"protobuf": 2, "grpcio": 1}
+
+
+def _golden_id(path: Path) -> str:
+    """Return a short pytest id derived from the golden case directory."""
+    # .../test_cookiecutter_generation/<case>/<repo>/pyproject.toml
+    return path.parent.parent.name
+
+
+def _extract_runtime_bound(text: str, name: str) -> tuple[str, int]:
+    """Return ``(floor, upper_major)`` for ``name`` from a pyproject text.
+
+    Uses the same shape the fixer's regex expects so that a template format
+    change makes this helper raise with a clear message before the test
+    fabricates a bogus dependabot payload.
+    """
+    pattern = rf'"{re.escape(name)}\s*>=\s*([^,"]+)\s*,\s*<\s*([^"]+)"'
+    matches = re.findall(pattern, text)
+    if len(matches) != 1:
+        raise AssertionError(
+            f"expected exactly one {name} runtime range in the golden "
+            f"pyproject.toml; found {len(matches)}: {matches!r}. The api "
+            "template format may have drifted from the fixer's contract."
+        )
+    floor, upper = matches[0]
+    return floor.strip(), int(upper.strip())
+
+
+def _bump_major(version: str) -> str:
+    """Return ``version`` with its major component incremented by one."""
+    match = re.match(r"v?(\d+)(.*)", version.strip())
+    if match is None:
+        raise AssertionError(f"could not parse version {version!r}")
+    return f"{int(match.group(1)) + 1}{match.group(2)}"
+
+
+def _major_number(version: str) -> int:
+    """Return the major number from a version string."""
+    match = re.match(r"\d+", version)
+    if match is None:
+        raise AssertionError(f"could not parse major number from {version!r}")
+    return int(match.group(0))
+
+
+def _make_dependabot_metadata(*, protobuf_version: str, grpcio_version: str) -> str:
+    """Build a realistic dependabot ``UPDATED_DEPENDENCIES_JSON`` payload."""
+    return json.dumps(
+        [
+            {
+                "dependencyName": "grpcio",
+                "dependencyType": "direct:production",
+                "updateType": "version-update:semver-major",
+                "directory": "/",
+                "packageEcosystem": "pip",
+                "newVersion": grpcio_version,
+            },
+            {
+                "dependencyName": "grpcio-tools",
+                "dependencyType": "direct:development",
+                "updateType": "version-update:semver-major",
+                "directory": "/",
+                "packageEcosystem": "pip",
+                "newVersion": grpcio_version,
+            },
+            {
+                "dependencyName": "protobuf",
+                "dependencyType": "direct:production",
+                "updateType": "version-update:semver-major",
+                "directory": "/",
+                "packageEcosystem": "pip",
+                "newVersion": protobuf_version,
+            },
+        ]
+    )
+
+
+@pytest.mark.parametrize("golden_pyproject", GOLDEN_API_PYPROJECTS, ids=_golden_id)
+def test_fixer_against_generated_api_pyproject(
+    golden_pyproject: Path,
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+    capsys: pytest.CaptureFixture[str],
+) -> None:
+    """Apply the fixer to a freshly generated API repo's ``pyproject.toml``.
+
+    This guards against template drift: if the API template stops emitting the
+    exact ``"<dep> >= X, < Y", # Do not widen beyond Y!`` shape that the fixer
+    relies on, the regex-based replacement will fail to find a match and this
+    test will surface the breakage.
+
+    The "new" versions injected via dependabot metadata are derived from the
+    golden file's current bounds (next major) so the test always exercises a
+    real bump even after the template's pinned versions get bumped.
+    """
+    assert GOLDEN_API_PYPROJECTS, (
+        "no api golden pyproject.toml fixtures discovered; refresh the golden "
+        "tree with `UPDATE_GOLDEN=1 pytest tests/integration/"
+        "test_cookiecutter_generation.py::test_golden`"
+    )
+
+    original = golden_pyproject.read_text(encoding="utf-8")
+
+    # Derive realistic "new" versions from the golden's current bounds. Bumping
+    # the major guarantees the fixer rewrites both the floor and the upper
+    # bound, even if the template later raises its pinned versions.
+    protobuf_floor, protobuf_upper = _extract_runtime_bound(original, "protobuf")
+    grpcio_floor, grpcio_upper = _extract_runtime_bound(original, "grpcio")
+    new_protobuf = _bump_major(protobuf_floor)
+    new_grpcio = _bump_major(grpcio_floor)
+    expected_protobuf_upper = (
+        _major_number(new_protobuf) + EXPECTED_UPPER_BOUND_OFFSETS["protobuf"]
+    )
+    expected_grpcio_upper = (
+        _major_number(new_grpcio) + EXPECTED_UPPER_BOUND_OFFSETS["grpcio"]
+    )
+    # Sanity: the derived "new" bounds must actually differ from the originals,
+    # otherwise the test would silently no-op.
+    assert new_protobuf != protobuf_floor
+    assert new_grpcio != grpcio_floor
+    assert expected_protobuf_upper != protobuf_upper
+    assert expected_grpcio_upper != grpcio_upper
+
+    workspace = tmp_path / fixer.PYPROJECT.name
+    shutil.copyfile(golden_pyproject, workspace)
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.setattr(sys, "argv", [str(FIXER_PATH)])
+    monkeypatch.setenv(
+        "UPDATED_DEPENDENCIES_JSON",
+        _make_dependabot_metadata(
+            protobuf_version=new_protobuf, grpcio_version=new_grpcio
+        ),
+    )
+
+    fixer.main()
+
+    captured = capsys.readouterr()
+    assert (
+        captured.out == "Updated pyproject.toml with 2 grpc/protobuf constraint(s).\n"
+    )
+    assert captured.err == ""
+
+    updated = workspace.read_text(encoding="utf-8")
+    expected_protobuf_line = (
+        f'"protobuf >= {new_protobuf}, < {expected_protobuf_upper}", '
+        f"# Do not widen beyond {expected_protobuf_upper}!"
+    )
+    expected_grpcio_line = (
+        f'"grpcio >= {new_grpcio}, < {expected_grpcio_upper}", '
+        f"# Do not widen beyond {expected_grpcio_upper}!"
+    )
+    assert expected_protobuf_line in updated
+    assert expected_grpcio_line in updated
+    # The original bounds must be gone (proves the rewrite actually happened).
+    assert f'"protobuf >= {protobuf_floor}, < {protobuf_upper}"' not in updated
+    assert f'"grpcio >= {grpcio_floor}, < {grpcio_upper}"' not in updated