test: add cloneFields tests

internal/observability/clone_test.go

@@ -0,0 +1,29 @@
+package observability
+
+import (
+	"testing"
+)
+
+func TestCloneFieldsReturnsNilForNil(t *testing.T) {
+	if got := cloneFields(nil); got != nil {
+		t.Fatalf("expected nil, got %#v", got)
+	}
+}
+
+func TestCloneFieldsReturnsNilForEmpty(t *testing.T) {
+	if got := cloneFields(map[string]any{}); got != nil {
+		t.Fatalf("expected nil, got %#v", got)
+	}
+}
+
+func TestCloneFieldsCopiesAllEntries(t *testing.T) {
+	original := map[string]any{"a": 1, "b": "two"}
+	cp := cloneFields(original)
+	if cp["a"] != 1 || cp["b"] != "two" {
+		t.Fatalf("clone = %#v, want %#v", cp, original)
+	}
+	cp["c"] = 3
+	if _, exists := original["c"]; exists {
+		t.Fatal("clone modified original")
+	}
+}