test: replace sleep-based test with deterministic channel verification

The cleanup routine test used time.Sleep() without actually verifying
the goroutine stopped. Added a done channel to provide deterministic
verification of goroutine termination.

Signed-off-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>

internal/cnpgi/instance/internal/client/client.go

@@ -55,6 +55,7 @@ type ExtendedClient struct {
 	cachedObjects   []cachedEntry
 	mux             *sync.Mutex
 	cleanupInterval time.Duration
+	cleanupDone     chan struct{} // Signals when cleanup routine exits
 }
 
 // NewExtendedClient returns an extended client capable of caching secrets on the 'Get' operation.
@@ -68,6 +69,7 @@ func NewExtendedClient(
 		Client:          baseClient,
 		mux:             &sync.Mutex{},
 		cleanupInterval: DefaultCleanupIntervalSeconds * time.Second,
+		cleanupDone:     make(chan struct{}),
 	}
 
 	// Start the background cleanup routine
@@ -225,6 +227,7 @@ func (e *ExtendedClient) Patch(
 // startCleanupRoutine periodically removes expired entries from the cache.
 // It runs until the context is cancelled.
 func (e *ExtendedClient) startCleanupRoutine(ctx context.Context) {
+	defer close(e.cleanupDone)
 	contextLogger := log.FromContext(ctx).WithName("extended_client_cleanup")
 	ticker := time.NewTicker(e.cleanupInterval)
 	defer ticker.Stop()

internal/cnpgi/instance/internal/client/client_test.go

@@ -302,10 +302,12 @@ var _ = Describe("ExtendedClient Cache Cleanup", func() {
 		// Cancel the context immediately
 		cancel()
 
-		// Give the goroutine time to stop
-		time.Sleep(50 * time.Millisecond)
-
-		// The goroutine should have stopped gracefully (no panic or hanging)
-		// This test mainly verifies the cleanup routine respects context cancellation
+		// Verify the cleanup routine actually stops by waiting for the done channel
+		select {
+		case <-ec.cleanupDone:
+			// Success: cleanup routine exited as expected
+		case <-time.After(1 * time.Second):
+			Fail("cleanup routine did not stop within timeout")
+		}
 	})
 })