Only wait for delayed queue if there is no work

The previous solution for processing the work queue sleeps after
processing every work item, which isn't ideal for responsive tests, and
it was resulting in flakes.

Instead, process work as fast as possible, and only sleep when the queue
is empty.

Note: analysis of the failing logs and the possible fix was assisted by
an "AI" agent.

Signed-off-by: Nolan Brubaker <nolan@nbrubaker.com>
Co-Authored-By: Claude Code <noreply@anthropic.com>

Author: nrb

pkg/controllers/tagging/tagging_controller_test.go

@@ -243,13 +243,26 @@ func Test_NodesJoiningAndLeaving(t *testing.T) {
 					time.Sleep(10 * time.Millisecond)
 				}
 
+				// Process all items, including those waiting in the rate limiter's delayed queue.
+				// The rate limiter has max delay of 5ms, so we wait longer than that when the
+				// queue appears empty to ensure delayed items have time to be re-added.
 				cnt := 0
-				for tc.workqueue.Len() > 0 {
-					tc.process(context.TODO())
-					cnt++
-					// sleep briefly because of exponential backoff when requeueing failed workitem
-					// resulting in workqueue to be empty if checked immediately
-					time.Sleep(7 * time.Millisecond)
+				emptyChecks := 0
+				const maxEmptyChecks = 3
+				const emptyCheckDelay = 20 * time.Millisecond // 4x the max rate limit delay of 5ms
+
+				for emptyChecks < maxEmptyChecks {
+					if tc.workqueue.Len() > 0 {
+						tc.process(context.TODO())
+						cnt++
+						emptyChecks = 0 // Reset since we found work
+						// No sleep here - process items as fast as possible
+					} else {
+						// Queue appears empty, but items might be in the delayed queue.
+						// Wait longer than the max rate limit delay before concluding we're done.
+						time.Sleep(emptyCheckDelay)
+						emptyChecks++
+					}
 				}
 
 				for _, msg := range testcase.expectedMessages {