refactor: separate test-only scalers from production code

controllers/keda/suite_test.go

@@ -36,7 +36,9 @@ import (
 	kedav1alpha1 "github.com/kedacore/keda/v2/apis/keda/v1alpha1"
 	"github.com/kedacore/keda/v2/pkg/eventemitter"
 	"github.com/kedacore/keda/v2/pkg/k8s"
+	"github.com/kedacore/keda/v2/pkg/scalers"
 	"github.com/kedacore/keda/v2/pkg/scalers/authentication"
+	"github.com/kedacore/keda/v2/pkg/scalers/scalersconfig"
 	"github.com/kedacore/keda/v2/pkg/scaling"
 )
 
@@ -59,6 +61,11 @@ func TestAPIs(t *testing.T) {
 var _ = BeforeSuite(func() {
 	logf.SetLogger(zap.New(zap.UseDevMode(true), zap.WriteTo(GinkgoWriter)))
 
+	// Register test-only scalers
+	scaling.RegisterTestScalerBuilder("external-mock", func(_ context.Context, _ client.Client, _ string, config *scalersconfig.ScalerConfig) (scalers.Scaler, error) {
+		return scalers.NewExternalMockScaler(config)
+	})
+
 	By("bootstrapping test environment")
 	testEnv = &envtest.Environment{
 		CRDDirectoryPaths:     []string{filepath.Join("..", "..", "config", "crd", "bases")},

pkg/scaling/scalers_builder.go

@@ -119,8 +119,22 @@ func (h *scaleHandler) buildScalers(ctx context.Context, withTriggers *kedav1alp
 	return result, nil
 }
 
+// function type for building test-only scalers
+type testScalerBuilder func(context.Context, client.Client, string, *scalersconfig.ScalerConfig) (scalers.Scaler, error)
+
+var testScalerBuilders = make(map[string]testScalerBuilder)
+
+func RegisterTestScalerBuilder(triggerType string, builder testScalerBuilder) {
+	testScalerBuilders[triggerType] = builder
+}
+
 // buildScaler builds a scaler form input config and trigger type
 func buildScaler(ctx context.Context, client client.Client, triggerType string, config *scalersconfig.ScalerConfig) (scalers.Scaler, error) {
+	// Check test scalers first (only populated during tests)
+	if builder, ok := testScalerBuilders[triggerType]; ok {
+		return builder(ctx, client, triggerType, config)
+	}
+
 	// TRIGGERS-START
 	switch triggerType {
 	case "activemq":
@@ -179,9 +193,6 @@ func buildScaler(ctx context.Context, client client.Client, triggerType string,
 		return scalers.NewEtcdScaler(config)
 	case "external":
 		return scalers.NewExternalScaler(config)
-	// TODO: use other way for test.
-	case "external-mock":
-		return scalers.NewExternalMockScaler(config)
 	case "external-push":
 		return scalers.NewExternalPushScaler(config)
 	case "forgejo-runner":

pkg/scaling/scalers_builder_registry_test.go

@@ -0,0 +1,37 @@
+package scaling
+
+import (
+	"context"
+	"testing"
+
+	"sigs.k8s.io/controller-runtime/pkg/client"
+
+	"github.com/kedacore/keda/v2/pkg/scalers"
+	"github.com/kedacore/keda/v2/pkg/scalers/scalersconfig"
+)
+
+func TestTestScalerRegistry(t *testing.T) {
+	called := false
+	RegisterTestScalerBuilder("test-scaler", func(_ context.Context, _ client.Client, _ string, _ *scalersconfig.ScalerConfig) (scalers.Scaler, error) {
+		called = true
+		return nil, nil
+	})
+
+	_, _ = buildScaler(context.Background(), nil, "test-scaler", &scalersconfig.ScalerConfig{})
+
+	if !called {
+		t.Error("Test scaler builder was not called")
+	}
+
+	delete(testScalerBuilders, "test-scaler")
+}
+
+func TestProductionScalerStillWorks(t *testing.T) {
+	// Verify that a production scaler like "cron" still returns an error with proper message
+	config := &scalersconfig.ScalerConfig{}
+	_, err := buildScaler(context.Background(), nil, "cron", config)
+
+	if err != nil && err.Error() == "no scaler found for type: cron" {
+		t.Error("Production scaler 'cron' was not found in buildScaler")
+	}
+}