docs: add docstrings to nested test helpers (#64)

tests/pycharting/api/test_interface.py

@@ -161,14 +161,18 @@ def test_plot_block_returns_when_shutdown_event_set():
     """
 
     class _Event:
+        """Fake shutdown event that reports "not set" once, then "set"."""
+
         def __init__(self):
             self._checks = 0
 
         def is_set(self):
+            """Return False on the first call, then True, yielding one loop iteration."""
             self._checks += 1
             return self._checks > 1  # False first, then True -> exactly one iteration
 
         def wait(self, timeout=None):
+            """Return immediately — the wait duration is irrelevant to this test."""
             return None
 
     n = 10
@@ -189,10 +193,14 @@ def test_plot_block_handles_keyboard_interrupt():
     """A Ctrl+C during the blocking wait stops the server and still returns success."""
 
     class _InterruptingEvent:
+        """Fake shutdown event whose wait raises ``KeyboardInterrupt``."""
+
         def is_set(self):
+            """Report the event as never set, so ``plot()`` enters the blocking wait."""
             return False
 
         def wait(self, timeout=None):
+            """Simulate a Ctrl+C arriving while the caller is blocked."""
             raise KeyboardInterrupt
 
     n = 10

tests/pycharting/core/test_lifecycle.py

@@ -282,6 +282,7 @@ def test_server_responds_after_start(wait_until):
     server = ChartServer()
 
     def _healthy():
+        """Return the health response once it comes back 200, else None to retry."""
         try:
             response = httpx.get(f"http://{server.host}:{server.port}/health", timeout=1)
         except httpx.HTTPError:
@@ -303,6 +304,7 @@ def test_server_accessible_in_background(wait_until):
     server = ChartServer()
 
     def _healthy():
+        """Return the health response once it comes back 200, else None to retry."""
         try:
             response = httpx.get(f"http://{server.host}:{server.port}/health", timeout=1)
         except httpx.HTTPError: