nlohmann-json 基本测试用例¶
项目地址：nlohmann-json
下面给你一套比较完整的 nlohmann-json.hpp 测试用例，适合：
- 单元测试
- CI 测试
- 验证 JSON 功能
- 学习 API
我按“基础 → 常用 → 异常 → 高级”来写。
0. 配置方法¶
cmake_minimum_required(VERSION 3.15)
project(TestJson)
set(CMAKE_CXX_STANDARD 17)
include(FetchContent)
FetchContent_Declare(
json
URL https://github.com/nlohmann/json/releases/download/v3.12.0/json.tar.xz
)
FetchContent_MakeAvailable(json)
add_executable(main main.cpp)
target_link_libraries(main PRIVATE nlohmann_json::nlohmann_json)
1. 空模板¶
#include <iostream>
#include "json.hpp"
using namespace std;
using json = nlohmann::json;
int main()
{
return 0;
}
2. 基础对象测试¶
#include <cassert>
#include <iostream>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
void test_basic_object()
{
json j;
j["name"] = "Alice";
j["age"] = 18;
j["is_student"] = true;
assert(j["name"] == "Alice");
assert(j["age"] == 18);
assert(j["is_student"] == true);
std::cout << "test_basic_object passed\n";
}
3. JSON 数组测试¶
void test_array()
{
json j = {
{"numbers", {1, 2, 3, 4}}
};
assert(j["numbers"].is_array());
assert(j["numbers"].size() == 4);
assert(j["numbers"][2] == 3);
std::cout << "test_array passed\n";
}
4. JSON 字符串解析¶
void test_parse()
{
std::string text = R"(
{
"title": "JSON",
"version": 3.12
}
)";
json j = json::parse(text);
assert(j["title"] == "JSON");
assert(j["version"] == 3.12);
std::cout << "test_parse passed\n";
}
5. dump 格式化测试¶
void test_dump()
{
json j = {
{"hello", "world"},
{"value", 123}
};
std::string s = j.dump(4);
assert(s.find("hello") != std::string::npos);
assert(s.find("world") != std::string::npos);
std::cout << s << std::endl;
std::cout << "test_dump passed\n";
}
6. 异常处理测试（重点）¶
void test_parse_exception()
{
std::string bad_json = R"(
{
"name": "Alice",
"age":
}
)";
try
{
json j = json::parse(bad_json);
assert(false); // 不应该到这里
}
catch (const json::parse_error& e)
{
std::cout << "parse exception caught:\n";
std::cout << e.what() << std::endl;
assert(true);
}
}
7. 类型检查测试¶
void test_type_check()
{
json j = {
{"id", 100},
{"name", "Bob"},
{"online", false}
};
assert(j["id"].is_number());
assert(j["name"].is_string());
assert(j["online"].is_boolean());
std::cout << "test_type_check passed\n";
}
8. 嵌套对象测试¶
void test_nested()
{
json j = {
{"user",
{
{"name", "Tom"},
{"email", "tom@test.com"}
}
}
};
assert(j["user"]["name"] == "Tom");
assert(j["user"]["email"] == "tom@test.com");
std::cout << "test_nested passed\n";
}
9. vector 自动转换¶
这是 nlohmann::json 很常用的功能。
#include <vector>
void test_vector()
{
std::vector<int> vec = {1,2,3,4};
json j = vec;
assert(j.is_array());
assert(j[0] == 1);
auto out = j.get<std::vector<int>>();
assert(out.size() == 4);
assert(out[3] == 4);
std::cout << "test_vector passed\n";
}
10. map 自动转换¶
#include <map>
void test_map()
{
std::map<std::string, int> scores = {
{"math", 90},
{"english", 85}
};
json j = scores;
assert(j["math"] == 90);
auto restored =
j.get<std::map<std::string, int>>();
assert(restored["english"] == 85);
std::cout << "test_map passed\n";
}
11. 自定义结构体序列化（核心高级功能）¶
这是企业项目最常用的。
struct User
{
std::string name;
int age;
};
NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE(
User,
name,
age
)
void test_custom_type()
{
User u {"Jack", 20};
json j = u;
assert(j["name"] == "Jack");
assert(j["age"] == 20);
User u2 = j.get<User>();
assert(u2.name == "Jack");
assert(u2.age == 20);
std::cout << "test_custom_type passed\n";
}
12. JSON Pointer 测试¶
void test_json_pointer()
{
json j = {
{"user",
{
{"name", "Alice"}
}
}
};
json::json_pointer ptr("/user/name");
assert(j[ptr] == "Alice");
std::cout << "test_json_pointer passed\n";
}
13. 完整 main¶
int main()
{
test_basic_object();
test_array();
test_parse();
test_dump();
test_parse_exception();
test_type_check();
test_nested();
test_vector();
test_map();
test_custom_type();
test_json_pointer();
std::cout << "\nALL TESTS PASSED\n";
return 0;
}