feat(v1): unify API response, validation, exception handling and tests

src/test/java/com/example/demo/controller/UserControllerTest.java

@@ -0,0 +1,62 @@
+package com.example.demo.controller;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.http.MediaType;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+class UserControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    void shouldListUsersWithApiResponseWrapper() throws Exception {
+        mockMvc.perform(get("/api/users"))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.code").value(0))
+                .andExpect(jsonPath("$.data").isArray());
+    }
+
+    @Test
+    void shouldCreateUser() throws Exception {
+        String json = """
+                {
+                  \"name\": \"测试用户\",
+                  \"email\": \"test@example.com\",
+                  \"age\": 22
+                }
+                """;
+
+        mockMvc.perform(post("/api/users")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content(json))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.code").value(0))
+                .andExpect(jsonPath("$.data.name").value("测试用户"));
+    }
+
+    @Test
+    void shouldRejectInvalidUser() throws Exception {
+        String json = """
+                {
+                  \"name\": \"\",
+                  \"email\": \"bad-mail\",
+                  \"age\": 222
+                }
+                """;
+
+        mockMvc.perform(post("/api/users")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content(json))
+                .andExpect(status().isBadRequest())
+                .andExpect(jsonPath("$.code").value(400));
+    }
+}