Introduce slowest-tests cli command

README.md

@@ -42,6 +42,11 @@ However, when there are major changes in the suite compared to what's stored in
 
 The splitting algorithm can be controlled with the `--splitting-algorithm` CLI option and defaults to `duration_based_chunks`. For more information about the different algorithms and their tradeoffs, please see the section below.
 
+### CLI commands
+#### slowest-tests
+Lists the slowest tests based on the information stored in the test durations file. See `slowest-tests help` for more
+ information.
+
 ## Interactions with other pytest plugins
 * [`pytest-random-order`](https://github.com/jbasko/pytest-random-order): ⚠️ The **default settings** of that plugin (setting only `--random-order` to activate it) are **incompatible** with `pytest-split`. Test selection in the groups happens after randomization, potentially causing some tests to be selected in several groups and others not at all. Instead, a global random seed needs to be computed before running the tests (for example using `$RANDOM` from the shell) and that single seed then needs to be used for all groups by setting the `--random-order-seed` option.
 

pyproject.toml

@@ -36,6 +36,9 @@ pre-commit = "^2.13.0"
 requires = ["poetry-core>=1.0.0"]
 build-backend = "poetry.core.masonry.api"
 
+[tool.poetry.scripts]
+slowest-tests = "pytest_split.cli:list_slowest_tests"
+
 [tool.poetry.plugins.pytest11]
 pytest-split = "pytest_split.plugin"
 

src/pytest_split/cli.py

@@ -0,0 +1,34 @@
+import argparse
+import json
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from typing import Dict
+
+
+def list_slowest_tests():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--durations-path",
+        help=(
+            "Path to the file in which durations are stored, "
+            "default is .test_durations in the current working directory"
+        ),
+        default=".test_durations",
+        type=argparse.FileType(),
+    )
+    parser.add_argument(
+        "-c",
+        "--count",
+        help="How many slowest to list",
+        default=10,
+        type=int,
+    )
+    args = parser.parse_args()
+    return _list_slowest_tests(json.load(args.durations_path), args.count)
+
+
+def _list_slowest_tests(durations: "Dict[str, float]", count: int) -> None:
+    slowest_tests = tuple(sorted(durations.items(), key=lambda item: item[1], reverse=True))[:count]
+    for test, duration in slowest_tests:
+        print(f"{duration:.2f} {test}")  # noqa: T001

tests/test_cli.py

@@ -0,0 +1,30 @@
+import argparse
+import json
+import sys
+from io import StringIO
+from unittest.mock import patch
+
+import pytest
+
+from pytest_split import cli
+
+
+@pytest.fixture
+def durations_file(tmpdir):
+    durations_path = str(tmpdir.join(".durations"))
+    durations = {f"test_{i}": float(i) for i in range(1, 11)}
+    with open(durations_path, "w") as f:
+        json.dump(durations, f)
+    with open(durations_path, "r") as f:
+        yield f
+
+
+def test_slowest_tests(durations_file):
+    with patch("pytest_split.cli.argparse.ArgumentParser", autospec=True) as arg_parser, patch(
+        "sys.stdout", new_callable=StringIO
+    ):
+        arg_parser().parse_args.return_value = argparse.Namespace(durations_path=durations_file, count=3)
+        cli.list_slowest_tests()
+
+        output = sys.stdout.getvalue()
+        assert output == "10.00 test_10\n" "9.00 test_9\n" "8.00 test_8\n"