Use fake HTTP servers in tests (WIP)

We introduce a few fixtures, defined in tests/conftest.py:

- patroni_api, an HTTP server serving files in a temporary directory and
  with an 'installed()' context manager method to be used in actual
  tests to setup expected responses based on specified JSON files,
- runner, a CliRunner, configured with stdout and stderr separated as
  logs of the HTTP server thread would appear in stderr, and if mixed
  with stdout, the assertions in test case will fail.

Fixtures use some logging in order to improve debugging.

The direct advantage of this is that PatroniResource.rest_api() method
is now covered by the test suite.

For test_api.py, there was no 'patroni.json' file in tests/json, so we
use a temporary file when serving the API.

tests/__init__.py

@@ -0,0 +1,43 @@
+import logging
+import shutil
+from contextlib import contextmanager
+from functools import partial
+from http.server import HTTPServer, SimpleHTTPRequestHandler
+from pathlib import Path
+from typing import Any, Iterator, Union
+
+logger = logging.getLogger(__name__)
+logger.setLevel(logging.DEBUG)
+
+
+class PatroniAPI(HTTPServer):
+    def __init__(self, directory: Path, *, datadir: Path) -> None:
+        self.directory = directory
+        self.datadir = datadir
+        handler_cls = partial(SimpleHTTPRequestHandler, directory=str(directory))
+        super().__init__(("", 0), handler_cls)
+
+    def serve_forever(self, *args: Any) -> None:
+        logger.info(
+            "starting fake Patroni API at %s (directory=%s)",
+            self.endpoint,
+            self.directory,
+        )
+        return super().serve_forever(*args)
+
+    @property
+    def endpoint(self) -> str:
+        return f"http://{self.server_name}:{self.server_port}"
+
+    @contextmanager
+    def installed(self, **installed: Union[Path, str]) -> Iterator[None]:
+        """Temporarilly install specified files in served directory."""
+        for dest, src in installed.items():
+            if isinstance(src, str):
+                src = self.datadir / src
+            shutil.copy(src, self.directory / dest)
+        try:
+            yield None
+        finally:
+            for i in installed:
+                (self.directory / i).unlink()

tests/conftest.py

@@ -1,9 +1,13 @@
 from functools import partial
-from typing import Any, Callable
+from pathlib import Path
+from threading import Thread
+from typing import Any, Callable, Iterator
 
 import pytest
+from click.testing import CliRunner
 from pytest_mock import MockerFixture
 
+from . import PatroniAPI
 from .tools import my_mock
 
 
@@ -28,3 +32,31 @@ def fake_restapi(
     mocker: MockerFixture, use_old_replica_state: bool
 ) -> Callable[..., Any]:
     return partial(my_mock, mocker, use_old_replica_state=use_old_replica_state)
+
+
+@pytest.fixture(scope="session")
+def datadir() -> Path:
+    return Path(__file__).parent / "json"
+
+
+@pytest.fixture(scope="session")
+def patroni_api(
+    tmp_path_factory: pytest.TempPathFactory,
+    datadir: Path,
+    use_old_replica_state: bool,  # XXX
+) -> Iterator[PatroniAPI]:
+    """A fake HTTP server for the Patroni API serving files from a temporary
+    directory.
+    """
+    httpd = PatroniAPI(tmp_path_factory.mktemp("api"), datadir=datadir)
+    t = Thread(target=httpd.serve_forever)
+    t.start()
+    yield httpd
+    httpd.shutdown()
+    t.join()
+
+
+@pytest.fixture
+def runner() -> CliRunner:
+    """A CliRunner with stdout and stderr not mixed."""
+    return CliRunner(mix_stderr=False)

tests/test_api.py

@@ -1,23 +1,27 @@
+from pathlib import Path
+
 from click.testing import CliRunner
 
 from check_patroni.cli import main
 
+from . import PatroniAPI
 
-def test_api_status_code_200(fake_restapi) -> None:
-    runner = CliRunner()
 
-    fake_restapi("node_is_pending_restart_ok")
-    result = runner.invoke(
-        main, ["-e", "https://10.20.199.3:8008", "node_is_pending_restart"]
-    )
+def test_api_status_code_200(
+    runner: CliRunner, patroni_api: PatroniAPI, tmp_path: Path
+) -> None:
+    patroni_json = tmp_path / "patroni.json"
+    patroni_json.write_text('{"pending_restart": false}')
+    with patroni_api.installed(patroni=patroni_json):
+        result = runner.invoke(
+            main, ["-e", patroni_api.endpoint, "node_is_pending_restart"]
+        )
     assert result.exit_code == 0
 
 
-def test_api_status_code_404(fake_restapi) -> None:
-    runner = CliRunner()
-
-    fake_restapi("Fake test", status=404)
+def test_api_status_code_404(runner: CliRunner, patroni_api: PatroniAPI) -> None:
+    # HTTP server using an empty (tmp) directory, thus responding with 404s.
     result = runner.invoke(
-        main, ["-e", "https://10.20.199.3:8008", "node_is_pending_restart"]
+        main, ["-e", patroni_api.endpoint, "node_is_pending_restart"]
     )
     assert result.exit_code == 3

tests/test_cluster_config_has_changed.py

@@ -1,20 +1,29 @@
 from pathlib import Path
+from typing import Iterator
 
 import nagiosplugin
+import pytest
 from click.testing import CliRunner
 
 from check_patroni.cli import main
 
+from . import PatroniAPI
 
-def test_cluster_config_has_changed_ok_with_hash(fake_restapi) -> None:
-    runner = CliRunner()
 
-    fake_restapi("cluster_config_has_changed")
+@pytest.fixture(scope="module", autouse=True)
+def _setup_patroni_api(patroni_api: PatroniAPI) -> Iterator[None]:
+    with patroni_api.installed(config="cluster_config_has_changed.json"):
+        yield None
+
+
+def test_cluster_config_has_changed_ok_with_hash(
+    runner: CliRunner, patroni_api: PatroniAPI
+) -> None:
     result = runner.invoke(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--hash",
             "96b12d82571473d13e890b893734e731",
@@ -28,20 +37,17 @@ def test_cluster_config_has_changed_ok_with_hash(fake_restapi) -> None:
 
 
 def test_cluster_config_has_changed_ok_with_state_file(
-    fake_restapi, tmp_path: Path
+    runner: CliRunner, patroni_api: PatroniAPI, tmp_path: Path
 ) -> None:
-    runner = CliRunner()
-
     state_file = tmp_path / "cluster_config_has_changed.state_file"
     with state_file.open("w") as f:
         f.write('{"hash": "96b12d82571473d13e890b893734e731"}')
 
-    fake_restapi("cluster_config_has_changed")
     result = runner.invoke(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--state-file",
             str(state_file),
@@ -54,15 +60,14 @@ def test_cluster_config_has_changed_ok_with_state_file(
     )
 
 
-def test_cluster_config_has_changed_ko_with_hash(fake_restapi) -> None:
-    runner = CliRunner()
-
-    fake_restapi("cluster_config_has_changed")
+def test_cluster_config_has_changed_ko_with_hash(
+    runner: CliRunner, patroni_api: PatroniAPI
+) -> None:
     result = runner.invoke(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--hash",
             "96b12d82571473d13e890b8937ffffff",
@@ -76,21 +81,18 @@ def test_cluster_config_has_changed_ko_with_hash(fake_restapi) -> None:
 
 
 def test_cluster_config_has_changed_ko_with_state_file_and_save(
-    fake_restapi, tmp_path: Path
+    runner: CliRunner, patroni_api: PatroniAPI, tmp_path: Path
 ) -> None:
-    runner = CliRunner()
-
     state_file = tmp_path / "cluster_config_has_changed.state_file"
     with state_file.open("w") as f:
         f.write('{"hash": "96b12d82571473d13e890b8937ffffff"}')
 
-    fake_restapi("cluster_config_has_changed")
     # test without saving the new hash
     result = runner.invoke(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--state-file",
             str(state_file),
@@ -115,7 +117,7 @@ def test_cluster_config_has_changed_ko_with_state_file_and_save(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--state-file",
             str(state_file),
@@ -136,17 +138,16 @@ def test_cluster_config_has_changed_ko_with_state_file_and_save(
     assert new_config_hash == "96b12d82571473d13e890b893734e731"
 
 
-def test_cluster_config_has_changed_params(fake_restapi, tmp_path: Path) -> None:
+def test_cluster_config_has_changed_params(
+    runner: CliRunner, patroni_api: PatroniAPI, tmp_path: Path
+) -> None:
     # This one is placed last because it seems like the exceptions are not flushed from stderr for the next tests.
-    runner = CliRunner()
-
     fake_state_file = tmp_path / "fake_file_name.state_file"
-    fake_restapi("cluster_config_has_changed")
     result = runner.invoke(
         main,
         [
             "-e",
-            "https://10.20.199.3:8008",
+            patroni_api.endpoint,
             "cluster_config_has_changed",
             "--hash",
             "640df9f0211c791723f18fc3ed9dbb95",

tests/test_cluster_has_leader.py

@@ -2,42 +2,34 @@
 
 from check_patroni.cli import main
 
+from . import PatroniAPI
 
-def test_cluster_has_leader_ok(fake_restapi) -> None:
-    runner = CliRunner()
 
-    fake_restapi("cluster_has_leader_ok")
-    result = runner.invoke(
-        main, ["-e", "https://10.20.199.3:8008", "cluster_has_leader"]
-    )
+def test_cluster_has_leader_ok(runner: CliRunner, patroni_api: PatroniAPI) -> None:
+    with patroni_api.installed(cluster="cluster_has_leader_ok.json"):
+        result = runner.invoke(main, ["-e", patroni_api.endpoint, "cluster_has_leader"])
     assert result.exit_code == 0
     assert (
         result.stdout
         == "CLUSTERHASLEADER OK - The cluster has a running leader. | has_leader=1;;@0\n"
     )
 
 
-def test_cluster_has_leader_ok_standby_leader(fake_restapi) -> None:
-    runner = CliRunner()
-
-    fake_restapi("cluster_has_leader_ok_standby_leader")
-    result = runner.invoke(
-        main, ["-e", "https://10.20.199.3:8008", "cluster_has_leader"]
-    )
+def test_cluster_has_leader_ok_standby_leader(
+    runner: CliRunner, patroni_api: PatroniAPI
+) -> None:
+    with patroni_api.installed(cluster="cluster_has_leader_ok_standby_leader.json"):
+        result = runner.invoke(main, ["-e", patroni_api.endpoint, "cluster_has_leader"])
     assert result.exit_code == 0
     assert (
         result.stdout
         == "CLUSTERHASLEADER OK - The cluster has a running leader. | has_leader=1;;@0\n"
     )
 
 
-def test_cluster_has_leader_ko(fake_restapi) -> None:
-    runner = CliRunner()
-
-    fake_restapi("cluster_has_leader_ko")
-    result = runner.invoke(
-        main, ["-e", "https://10.20.199.3:8008", "cluster_has_leader"]
-    )
+def test_cluster_has_leader_ko(runner: CliRunner, patroni_api: PatroniAPI) -> None:
+    with patroni_api.installed(cluster="cluster_has_leader_ko.json"):
+        result = runner.invoke(main, ["-e", patroni_api.endpoint, "cluster_has_leader"])
     assert result.exit_code == 2
     assert (
         result.stdout