Don't watch the whole directory in the file watcher test (#326)

When watching the whole test directory we'll also get some events for
the directory, and those events can come with different order depending
on the OS, so we can't rely on them. We check that if a directory event
comes, it is a modification.

Also when testing for events in a file watcher, we need to set the
`polling_interval` to a value that is small enough to detect the changes
we are expecting, otherwise some events could be "merged" if the changes
happen faster than the polling interval.

Fixes #324.

Author: llucax

tests/test_file_watcher_integration.py

@@ -10,7 +10,7 @@
 import pytest
 
 from frequenz.channels import ReceiverStoppedError, select, selected_from
-from frequenz.channels.file_watcher import Event, EventType, FileWatcher
+from frequenz.channels.file_watcher import EventType, FileWatcher
 from frequenz.channels.timer import SkipMissedAndDrift, Timer
 
 
@@ -26,19 +26,28 @@ async def test_file_watcher(tmp_path: pathlib.Path) -> None:
     number_of_writes = 0
     expected_number_of_writes = 3
 
-    file_watcher = FileWatcher(paths=[str(tmp_path)])
+    file_watcher = FileWatcher(
+        paths=[str(tmp_path)], polling_interval=timedelta(seconds=0.05)
+    )
     timer = Timer(timedelta(seconds=0.1), SkipMissedAndDrift())
 
     async for selected in select(file_watcher, timer):
         if selected_from(selected, timer):
             filename.write_text(f"{selected.message}")
         elif selected_from(selected, file_watcher):
             event_type = EventType.CREATE if number_of_writes == 0 else EventType.MODIFY
-            assert selected.message == Event(type=event_type, path=filename)
-            number_of_writes += 1
-            # After receiving a write 3 times, unsubscribe from the writes channel
-            if number_of_writes == expected_number_of_writes:
-                break
+            event = selected.message
+            # If we receive updates for the directory itself, they should be only
+            # modifications, we only check that because we can have ordering issues if
+            # we try check also the order compared to events in the file.
+            if event.path == tmp_path:
+                assert event.type == EventType.MODIFY
+            elif event.path == filename:
+                assert event.type == event_type
+                number_of_writes += 1
+                # After receiving a write 3 times, unsubscribe from the writes channel
+                if number_of_writes == expected_number_of_writes:
+                    break
 
     assert number_of_writes == expected_number_of_writes
 
@@ -58,6 +67,7 @@ async def test_file_watcher_deletes(tmp_path: pathlib.Path) -> None:
         paths=[str(tmp_path)],
         event_types={EventType.DELETE},
         force_polling=False,
+        polling_interval=timedelta(seconds=0.05),
     )
     write_timer = Timer(timedelta(seconds=0.1), SkipMissedAndDrift())
     deletion_timer = Timer(timedelta(seconds=0.25), SkipMissedAndDrift())