test: add discovery tests proving end-to-end plugin loading

src/proxy_pool/plugins/discovery.py

@@ -22,7 +22,7 @@ def discover_plugins(
         logger.warning("Plugin package '%s' not found, skipping", package)
         return
 
-    if hasattr(mod, "__path__"):
+    if not hasattr(mod, "__path__"):
         logger.warning(
             "Plugin package '%s' has no __path__ attribute, skipping", package
         )

tests/unit/test_plugin_discovery.py

@@ -0,0 +1,40 @@
+from proxy_pool.config import Settings, DatabaseSettings
+from proxy_pool.plugins.discovery import discover_plugins
+from proxy_pool.plugins.registry import PluginRegistry
+
+
+def test_discovers_builtin_parsers():
+    settings = Settings(
+        secret_key="test",
+        db=DatabaseSettings(url="postgresql+asyncpg://localhost/test"),
+    )
+    registry = PluginRegistry()
+
+    discover_plugins("proxy_pool.plugins.builtin.parsers", registry, settings)
+
+    assert "plaintext" in registry.parsers
+
+
+def test_discovers_builtin_checkers():
+    settings = Settings(
+        secret_key="test",
+        db=DatabaseSettings(url="postgresql+asyncpg://localhost/test"),
+    )
+    registry = PluginRegistry()
+
+    discover_plugins("proxy_pool.plugins.builtin.checkers", registry, settings)
+
+    assert len(registry.checkers) > 0
+    assert registry.checkers[0].name == "tcp_connect"
+
+
+def test_skips_unconfigured_notifiers():
+    settings = Settings(
+        secret_key="test",
+        db=DatabaseSettings(url="postgresql+asyncpg://localhost/test"),
+    )
+    registry = PluginRegistry()
+
+    discover_plugins("proxy_pool.plugins.builtin.notifiers", registry, settings)
+
+    assert len(registry.notifiers) == 0