operator/pkg/util/apiclient: unit test wait

In this commit, we unit test the ait apiclient on waiting for API server,
API service, all pods constraint, some pods constraint, and the exponential
backoff utility.

operator/pkg/util/apiclient/wait.go

@@ -36,6 +36,18 @@ const (
 	APICallRetryInterval = 500 * time.Millisecond
 )
 
+var (
+	// initialBackoffDuration defines the initial duration for the backoff mechanism,
+	// set to 5 seconds. This value is used to determine the wait time before retrying
+	// a failed command.
+	initialBackoffDuration = 5 * time.Second
+
+	// backoffTimeoutFactor is the factor by which the backoff duration is multiplied
+	// after each failure. In this case, it is set to 2, meaning the wait time will
+	// double with each consecutive failure.
+	backoffTimeoutFactor float64 = 2
+)
+
 // Waiter is an interface for waiting for criteria in Karmada to happen
 type Waiter interface {
 	// WaitForAPI waits for the API Server's /healthz endpoint to become "ok"
@@ -79,9 +91,13 @@ func (w *KarmadaWaiter) WaitForAPI() error {
 	})
 }
 
+var aggregateClientFromConfigBuilder = func(karmadaConfig *rest.Config) (aggregator.Interface, error) {
+	return aggregator.NewForConfig(karmadaConfig)
+}
+
 // WaitForAPIService waits for the APIService condition to become "true"
 func (w *KarmadaWaiter) WaitForAPIService(name string) error {
-	aggregateClient, err := aggregator.NewForConfig(w.karmadaConfig)
+	aggregateClient, err := aggregateClientFromConfigBuilder(w.karmadaConfig)
 	if err != nil {
 		return err
 	}
@@ -162,20 +178,21 @@ func (w *KarmadaWaiter) SetTimeout(timeout time.Duration) {
 	w.timeout = timeout
 }
 
-// TryRunCommand runs a function a maximum of failureThreshold times, and retries on error. If failureThreshold is hit; the last error is returned
+// TryRunCommand runs a function a maximum of failureThreshold times, and
+// retries on error. If failureThreshold is hit; the last error is returned.
 func TryRunCommand(f func() error, failureThreshold int) error {
 	backoff := wait.Backoff{
-		Duration: 5 * time.Second,
-		Factor:   2, // double the timeout for every failure
+		Duration: initialBackoffDuration,
+		Factor:   backoffTimeoutFactor,
 		Steps:    failureThreshold,
 	}
 	return wait.ExponentialBackoff(backoff, func() (bool, error) {
 		err := f()
 		if err != nil {
-			// Retry until the timeout
+			// Retry until the timeout.
 			return false, nil
 		}
-		// The last f() call was a success, return cleanly
+		// The last f() call was a success, return cleanly.
 		return true, nil
 	})
 }