Improve tests to verify converted values

Author: Shashwati

cpp/src/arrow/json/parser_test.cc

@@ -182,9 +182,13 @@ TEST_P(BlockParserTypeError, AllowNumberToStringConversion) {
   std::shared_ptr<Array> parsed;
   ASSERT_OK(ParseFromString(options, "{\"a\":\"123\"}\n{\"a\":456}", &parsed));
   auto struct_array = std::static_pointer_cast<StructArray>(parsed);
+  ASSERT_NE(struct_array, nullptr);
   auto field_array = struct_array->GetFieldByName("a");
   ASSERT_NE(field_array, nullptr);
   ASSERT_EQ(field_array->length(), 2);
+  // Verify both values are strings (the number 456 should be converted to "456")
+  auto expected = ArrayFromJSON(utf8(), R"(["123", "456"])");
+  AssertUnconvertedArraysEqual(*expected, *field_array);
 }
 
 TEST_P(BlockParserTypeError, AllowStringToNumberConversion) {
@@ -193,9 +197,13 @@ TEST_P(BlockParserTypeError, AllowStringToNumberConversion) {
   std::shared_ptr<Array> parsed;
   ASSERT_OK(ParseFromString(options, "{\"a\":123}\n{\"a\":\"456\"}", &parsed));
   auto struct_array = std::static_pointer_cast<StructArray>(parsed);
+  ASSERT_NE(struct_array, nullptr);
   auto field_array = struct_array->GetFieldByName("a");
   ASSERT_NE(field_array, nullptr);
   ASSERT_EQ(field_array->length(), 2);
+  // Verify both values are numbers (the string "456" should be converted to 456)
+  auto expected = ArrayFromJSON(int64(), R"([123, 456])");
+  AssertUnconvertedArraysEqual(*expected, *field_array);
 }
 
 TEST_P(BlockParserTypeError, FailOnNestedInconvertible) {