fix: resolve __init__ complexity and harden analytics_url tests

  Extract _ensure_trailing_slash to bring Flagsmith.__init__ back under the
  flake8 C901 limit that pre-commit.ci flagged. Add an integration test for
  the default analytics endpoint, and filter both analytics tests by exact
  URL so they no longer depend on the global session's cross-test traffic.

Author: adamvialpando

flagsmith/flagsmith.py

@@ -178,19 +178,13 @@ def __init__(
             self.session.proxies.update(proxies or {})
             retries = retries or Retry(total=3, backoff_factor=0.1)
 
-            api_url = api_url or DEFAULT_API_URL
-            self.api_url = api_url if api_url.endswith("/") else f"{api_url}/"
-
-            realtime_api_url = realtime_api_url or DEFAULT_REALTIME_API_URL
-            self.realtime_api_url = (
-                realtime_api_url
-                if realtime_api_url.endswith("/")
-                else f"{realtime_api_url}/"
+            self.api_url = self._ensure_trailing_slash(api_url or DEFAULT_API_URL)
+            self.realtime_api_url = self._ensure_trailing_slash(
+                realtime_api_url or DEFAULT_REALTIME_API_URL
+            )
+            self.analytics_url = (
+                self._ensure_trailing_slash(analytics_url) if analytics_url else None
             )
-
-            if analytics_url and not analytics_url.endswith("/"):
-                analytics_url = f"{analytics_url}/"
-            self.analytics_url = analytics_url
 
             self.request_timeout_seconds = request_timeout_seconds
             self.session.mount(self.api_url, HTTPAdapter(max_retries=retries))
@@ -219,6 +213,10 @@ def __init__(
                 event_processor_config=event_processor_config,
             )
 
+    @staticmethod
+    def _ensure_trailing_slash(url: str) -> str:
+        return url if url.endswith("/") else f"{url}/"
+
     def _initialise_analytics(
         self,
         environment_key: str,

tests/test_flagsmith.py

@@ -1216,14 +1216,59 @@ def test_flagsmith_posts_analytics_to_analytics_url_when_set(
 
     # Then exactly one analytics POST landed on the override host (with the
     # trailing slash applied), carried the tracked feature payload, and the
-    # Edge Proxy never received an analytics request.
-    analytics_calls = [
-        call for call in responses.calls if call.request.method == "POST"
+    # Edge Proxy never received an analytics request. We filter by the exact
+    # analytics URL rather than counting all POSTs, because the module-global
+    # analytics session can leak background requests from other tests.
+    analytics_posts = [
+        call
+        for call in responses.calls
+        if call.request.method == "POST" and call.request.url == expected_analytics_url
     ]
-    assert len(analytics_calls) == 1
-    request = analytics_calls[0].request
-    assert request.url == expected_analytics_url
-    assert "edge-proxy" not in request.url
+    assert len(analytics_posts) == 1
+    request = analytics_posts[0].request
     assert request.body is not None
     assert json.loads(request.body) == {"some_feature": 1}
     assert request.headers["X-Environment-Key"] == api_key
+    assert not [
+        call
+        for call in responses.calls
+        if call.request.method == "POST" and "edge-proxy" in call.request.url
+    ]
+
+
+@responses.activate()
+def test_flagsmith_posts_analytics_to_api_url_when_analytics_url_unset(
+    api_key: str, flags_json: str, mocker: MockerFixture
+) -> None:
+    # Given a Flagsmith client with analytics enabled but no analytics_url
+    # override. This is the backwards-compatible default: analytics must keep
+    # posting to <api_url>/analytics/flags/, derived from api_url alone.
+    #
+    # As above, swap the FuturesSession for a synchronous requests.Session so
+    # the analytics POST is observable on the test thread.
+    mocker.patch("flagsmith.analytics.session", requests.Session())
+    flagsmith = Flagsmith(
+        environment_key=api_key,
+        api_url="http://core-api.flagsmith.com/api/v1/",
+        enable_analytics=True,
+    )
+
+    expected_analytics_url = "http://core-api.flagsmith.com/api/v1/analytics/flags/"
+    responses.add(method="GET", url=flagsmith.environment_flags_url, body=flags_json)
+    responses.add(method="POST", url=expected_analytics_url, status=200)
+
+    # When the evaluation API is exercised and analytics flushed deterministically.
+    flags = flagsmith.get_environment_flags()
+    assert flags.is_feature_enabled("some_feature") is True
+    assert flagsmith._analytics_processor is not None
+    flagsmith._analytics_processor.flush()
+
+    # Then exactly one analytics POST landed on the api_url-derived endpoint.
+    # Filter by the exact URL to stay robust against background requests leaked
+    # by the module-global analytics session in other tests.
+    analytics_posts = [
+        call
+        for call in responses.calls
+        if call.request.method == "POST" and call.request.url == expected_analytics_url
+    ]
+    assert len(analytics_posts) == 1