Fix Lockfile Schematics

internal/topdata/topdata_test.go

@@ -108,6 +108,29 @@ func TestResolvedTableRegistryRegistersConsistentTables(t *testing.T) {
 	}
 }
 
+func TestSaveLockfilePreservesExistingOrderAndAppendsNewKeys(t *testing.T) {
+	root := t.TempDir()
+	lockPath := filepath.Join(root, "lock.json")
+	writeFile(t, lockPath, "{\n  \"b\": 2,\n  \"a\": 1\n}\n")
+
+	if err := saveLockfile(lockPath, map[string]int{
+		"b": 2,
+		"a": 1,
+		"c": 3,
+	}); err != nil {
+		t.Fatalf("saveLockfile failed: %v", err)
+	}
+
+	got, err := os.ReadFile(lockPath)
+	if err != nil {
+		t.Fatalf("read lockfile: %v", err)
+	}
+	want := "{\n  \"b\": 2,\n  \"a\": 1,\n  \"c\": 3\n}\n"
+	if string(got) != want {
+		t.Fatalf("unexpected lockfile contents:\n%s", string(got))
+	}
+}
+
 func TestResolvedTableRegistryRejectsDuplicateKeys(t *testing.T) {
 	_, err := newResolvedTableRegistry([]nativeCollectedDataset{
 		{