testenv: Remove klog init flags

Removes klog.InitFlags() because the klog flags aren't parsed before
using klog. To avoid conflicting with other flags, it's better to not
populate the global flagset.
This results in default klogr to be set as the default
controller-runtime logger if not set in the test already. The logger
setup not being in init() allows users to set their own logger before
creating testenv Environment.

Signed-off-by: Sunny <darkowlzz@protonmail.com>

runtime/testenv/testenv.go

@@ -52,13 +52,6 @@ var (
 	env *envtest.Environment
 )
 
-func init() {
-	klog.InitFlags(nil)
-	logger := klogr.New()
-	log.SetLogger(logger)
-	ctrl.SetLogger(logger)
-}
-
 var (
 	cacheSyncBackoff = wait.Backoff{
 		Duration: 100 * time.Millisecond,
@@ -118,7 +111,32 @@ func WithCRDPath(path ...string) Option {
 //
 // NOTE: This function should be called only once for each package you are running tests within, usually the environment
 // is initialised in a suite_test.go or <package>_test.go file within a `TestMain` function.
+//
+// When a testenv Environment is created, it initializes the
+// controller-runtime's deferred logger with a default logger based on klog. In
+// order to override this behavior, the controller-runtime logger can be
+// initialized before creating testenv Environment.
+//
+//  import (
+//      "testing"
+//
+//      "github.com/fluxcd/pkg/runtime/testenv"
+//      ctrl "sigs.k8s.io/controller-runtime"
+//      "sigs.k8s.io/controller-runtime/pkg/log/zap"
+//  }
+//
+//  func TestMain(m *testing.M) {
+//      zlog := zap.New(zap.UseDevMode(true))
+//      ctrl.SetLogger(zlog)
+//
+//      testEnv = testenv.New()
+//      ...
+//  }
+//
 func New(o ...Option) *Environment {
+	// Set a default logger if not set already.
+	log.SetLogger(klogr.New())
+
 	opts := options{}
 	for _, apply := range o {
 		apply(&opts)