move to seperate function and add unit tests, ensuring coverage of change

Author: keithfz

internal/controller/promotions/promotions.go

@@ -477,14 +477,7 @@ func (r *reconciler) promote(
 		}
 	}
 
-	creator := "N/A"
-	actorAnnotation, ok := promo.ObjectMeta.Annotations[kargoapi.AnnotationKeyCreateActor]
-	if ok {
-		substrings := strings.Split(actorAnnotation, ":")
-		if len(substrings) == 2 {
-			creator = substrings[1]
-		}
-	}
+	creator := parseActorAnnotation(&promo)
 
 	promoCtx := directives.PromotionContext{
 		UIBaseURL:             r.cfg.APIServerBaseURL,
@@ -654,3 +647,15 @@ func (r *reconciler) terminatePromotion(
 
 	return nil
 }
+
+func parseActorAnnotation(promo *kargoapi.Promotion) string {
+	creator := "N/A"
+	actorAnnotation, ok := promo.ObjectMeta.Annotations[kargoapi.AnnotationKeyCreateActor]
+	if ok {
+		substrings := strings.Split(actorAnnotation, ":")
+		if len(substrings) == 2 {
+			creator = substrings[1]
+		}
+	}
+	return creator
+}

internal/controller/promotions/promotions_test.go

@@ -336,6 +336,60 @@ func TestReconcile(t *testing.T) {
 	}
 }
 
+func Test_parseActorAnnotation(t *testing.T) {
+	tests := []struct {
+		name            string
+		promo           *kargoapi.Promotion
+		expectedCreator string
+	}{
+		{
+			name: "basic case",
+			promo: &kargoapi.Promotion{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "fake-promo",
+					Namespace: "fake-namespace",
+					Annotations: map[string]string{
+						kargoapi.AnnotationKeyCreateActor: "email:fake-actor",
+					},
+				},
+			},
+			expectedCreator: "fake-actor",
+		},
+		{
+
+			name: "no annotation",
+			promo: &kargoapi.Promotion{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "fake-promo",
+					Namespace: "fake-namespace",
+				},
+			},
+			expectedCreator: "N/A",
+		},
+		{
+			name: "invalid",
+			promo: &kargoapi.Promotion{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "fake-promo",
+					Namespace: "fake-namespace",
+					Annotations: map[string]string{
+						kargoapi.AnnotationKeyCreateActor: "abc123",
+					},
+				},
+			},
+			expectedCreator: "N/A",
+		},
+	}
+
+	for _, tc := range tests {
+
+		t.Run(tc.name, func(t *testing.T) {
+			result := parseActorAnnotation(tc.promo)
+			require.Equal(t, tc.expectedCreator, result)
+		})
+	}
+}
+
 func Test_reconciler_terminatePromotion(t *testing.T) {
 	scheme := k8sruntime.NewScheme()
 	require.NoError(t, kargoapi.SchemeBuilder.AddToScheme(scheme))