fix append cases

Author: dreamer-coding

code/tests/cases/test_cstring.c

@@ -337,10 +337,11 @@ FOSSIL_TEST(c_test_cstring_strip_quotes) {
 
 FOSSIL_TEST(c_test_cstring_append) {
     cstring str = fossil_io_cstring_create("Hello");
-    int rc = fossil_io_cstring_append(&str, ", World!");
-    ASSUME_ITS_EQUAL_I32(0, rc);
-    ASSUME_ITS_EQUAL_CSTR("Hello, World!", str);
+    cstring result = fossil_io_cstring_append(str, ", World!");
+    ASSUME_NOT_CNULL(result);
+    ASSUME_ITS_EQUAL_CSTR("Hello, World!", result);
     fossil_io_cstring_free(str);
+    fossil_io_cstring_free(result);
 }
 
 // * * * * * * * * * * * * * * * * * * * * * * * *

code/tests/cases/test_cstring.cpp

@@ -304,10 +304,11 @@ FOSSIL_TEST(cpp_test_cstring_strip_quotes) {
 
 FOSSIL_TEST(cpp_test_cstring_append) {
     cstring str = fossil_io_cstring_create("Hello");
-    int rc = fossil_io_cstring_append(&str, ", World!");
-    ASSUME_ITS_EQUAL_I32(0, rc);
-    ASSUME_ITS_EQUAL_CSTR("Hello, World!", str);
+    cstring result = fossil_io_cstring_append(str, ", World!");
+    ASSUME_NOT_CNULL(result);
+    ASSUME_ITS_EQUAL_CSTR("Hello, World!", result);
     fossil_io_cstring_free(str);
+    fossil_io_cstring_free(result);
 }
 
 FOSSIL_TEST(cpp_test_cstring_stream_create_and_free) {