莫科托示例中的thenthrow（）方法

方案：模拟服务异常以测试控制器中的错误处理

1. Spring Boot 应用代码

Employee.java

package com.example.demo.model;public class Employee {    private String id;    private String name;    // constructors, getters, and setters    public Employee(String id, String name) {        this.id = id;        this.name = name;    }    public String getId() {        return id;    }    public void setId(String id) {        this.id = id;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }}

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package com.example.demo.exception;public class EmployeeNotFoundException extends RuntimeException {    public EmployeeNotFoundException(String message) {        super(message);    }}

登录后复制EmployeeService.java

package com.example.demo.service;import com.example.demo.exception.EmployeeNotFoundException;import com.example.demo.model.Employee;import org.springframework.stereotype.Service;@Servicepublic class EmployeeService {    public Employee getEmployeeById(String id) {        // 模拟员工不存在时抛出异常        if ("0".equals(id)) {            throw new EmployeeNotFoundException("Employee not found with id: " + id);        }        return new Employee(id, "John Doe");    }}

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package com.example.demo.controller;import com.example.demo.exception.EmployeeNotFoundException;import com.example.demo.model.Employee;import com.example.demo.service.EmployeeService;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.*;@RestController@RequestMapping("/employees")public class EmployeeController {    private final EmployeeService employeeService;    public EmployeeController(EmployeeService employeeService) {        this.employeeService = employeeService;    }    @GetMapping("/{id}")    public ResponseEntity getEmployee(@PathVariable String id) {        Employee employee = employeeService.getEmployeeById(id);        return ResponseEntity.ok(employee);    }    // 全局异常处理    @ExceptionHandler(EmployeeNotFoundException.class)    public ResponseEntity handleEmployeeNotFoundException(EmployeeNotFoundException ex) {        return new ResponseEntity(ex.getMessage(), HttpStatus.NOT_FOUND);    }}

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2. 使用 thenThrow() 的单元测试

EmployeeControllerTest.java

package com.example.demo.controller;import com.example.demo.exception.EmployeeNotFoundException;import com.example.demo.model.Employee;import com.example.demo.service.EmployeeService;import org.junit.jupiter.api.Test;import org.mockito.InjectMocks;import org.mockito.Mock;import org.mockito.MockitoAnnotations;import org.springframework.http.ResponseEntity;import static org.junit.jupiter.api.Assertions.*;import static org.mockito.Mockito.*;class EmployeeControllerTest {    @Mock    private EmployeeService employeeService;    @InjectMocks    private EmployeeController employeeController;    public EmployeeControllerTest() {        MockitoAnnotations.openMocks(this); // 初始化 Mock 对象    }    @Test    void testGetEmployee_Success() {        // Arrange: 模拟服务方法返回一个 Employee 对象        when(employeeService.getEmployeeById("1")).thenReturn(new Employee("1", "John Doe"));        // Act: 调用控制器方法        ResponseEntity response = employeeController.getEmployee("1");        // Assert: 验证响应是否正确        assertNotNull(response);        assertEquals(200, response.getStatusCodeValue());        assertEquals("John Doe", response.getBody().getName());        // 验证服务方法被调用了一次        verify(employeeService, times(1)).getEmployeeById("1");    }    @Test    void testGetEmployee_ThrowsException() {        // Arrange: 模拟服务方法抛出异常        when(employeeService.getEmployeeById("0")).thenThrow(new EmployeeNotFoundException("Employee not found with id: 0"));        // Act & Assert: 验证异常是否被正确处理        assertThrows(EmployeeNotFoundException.class, () -> {            employeeController.getEmployee("0");        });        // 验证服务方法被调用了一次        verify(employeeService, times(1)).getEmployeeById("0");    }}

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说明:

thenThrow() 的用法：when(employeeService.getEmployeeById(“0”)).thenThrow(new EmployeeNotFoundException(“Employee not found with id: 0”)); 这行代码模拟了当 getEmployeeById 方法传入 “0” 时抛出 EmployeeNotFoundException 异常。

单元测试包含两个测试用例：

testGetEmployee_Success: 测试成功获取员工信息的情况。testGetEmployee_ThrowsException: 测试员工不存在，服务抛出异常的情况，并验证异常被正确处理。

thenThrow() 的优点:

模拟真实世界的错误处理，无需修改实际服务代码。方便测试各种异常场景，例如数据库错误、数据丢失、API 失败等。确保在发生错误时，应用返回正确的响应。

结论:

使用 Mockito 的 thenThrow() 方法，可以有效地测试异常处理逻辑，而无需依赖实际的服务实现。 这使得单元测试更加简洁、可靠，并且易于维护。

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