这一篇主要讲使用Spock如何测试代码中抛异常的场景

背景

有些方法需要抛出异常来中断或控制流程，比如参数校验的逻辑: 不能为null，不符合指定的类型，list不能为空等验证，如果校验不通过则抛出checked异常，这个异常一般都是我们封装的业务异常信息，比如下面的业务代码：

 * 校验请求参数user是否合法
 * @param user
 * @throws APIException
public void validateUser(UserVO user) throws APIException {
    if(user == null){
        throw new APIException("10001", "user is null");
    if(null == user.getName() || "".equals(user.getName())){
        throw new APIException("10002", "user name is null");
    if(user.getAge() == 0){
        throw new APIException("10003", "user age is null");
    if(null == user.getTelephone() || "".equals(user.getTelephone())){
        throw new APIException("10004", "user telephone is null");
    if(null == user.getSex() || "".equals(user.getSex())){
        throw new APIException("10005", "user sex is null");
    if(null == user.getUserOrders() || user.getUserOrders().size() <= 0){
        throw new APIException("10006", "user order is null");
    for(OrderVO order : user.getUserOrders()) {
        if (null == order.getOrderNum() || "".equals(order.getOrderNum())) {
            throw new APIException("10007", "order number is null");
        if (null == order.getAmount()) {
            throw new APIException("10008", "order amount is null");
}

APIException 是我们封装的业务异常，主要包含 errorCode ， errorMessage 属性：

 * 自定义业务异常
public class APIException extends RuntimeException {
    private String errorCode;
    private String errorMessage;
    setXXX...
    getXXX...
}

这个大家应该都很熟悉，针对这种抛出多个不同错误码和错误信息的异常，如果我们使用Junit的方式测试，会比较麻烦，就目前我使用过的方法，如果是单个异常还好，多个的就不太好写测试代码

最常见的写法可能是下面这样:

@Test 
public void testException() {
  UserVO user = null;
  try {
    validateUser(user);
  } catch (APIException e) {
    assertThat(e.getErrorCode(), "10001");
    assertThat(e.getErrorMessage(), "user is null");
  UserVO user = new UserVO();
  try {
    validateUser(user);
  } catch (APIException e) {
    assertThat(e.getErrorCode(), "10002");
    assertThat(e.getErrorMessage(), "user name is null");
}

当然可以使用junit的 ExpectedException 方式:

@Rule
public [ExpectedException](http://javakk.com/tag/expectedexception "查看更多关于 ExpectedException 的文章") exception = ExpectedException.none();
exception.expect(APIException.class); // 验证抛出异常的类型是否符合预期
exception.expectMessage("Order Flight return null exception"); //验证抛出异常的错误信息

或者使用 @Test(expected = APIException.class) 注解

但这两种方式都有缺陷:

@Test 方式不能指定断言的异常属性，比如errorCode，errorMessage

ExpectedException 的方式也只提供了expectMessage的api，对自定义的errorCode不支持，尤其像上面的有很多分支抛出多种不同异常码的情况

thrown

我们来看下Spock是如何解决的，Spock内置thrown()方法，可以捕获调用业务代码抛出的预期异常并验证，再结合where表格的功能，可以很方便的覆盖多种自定义业务异常，代码如下:

 * 校验用户请求参数的测试类
 * @author 公众号:Java老K
 * 个人博客:www.javakk.com
class UserControllerTest extends Specification {
    def userController = new UserController()
    @Unroll
    def "验证用户信息的合法性: #expectedMessage"() {
        when: "调用校验用户方法"
        userController.validateUser(user)
        then: "捕获异常并设置需要验证的异常值"
        def exception = thrown(expectedException)
        exception.errorCode == expectedErrCode
        exception.errorMessage == expectedMessage
        where: "表格方式验证用户信息的合法性"
        user           || expectedException | expectedErrCode | expectedMessage
        getUser(10001) || APIException      | "10001"         | "user is null"
        getUser(10002) || APIException      | "10002"         | "user name is null"
        getUser(10003) || APIException      | "10003"         | "user age is null"
        getUser(10004) || APIException      | "10004"         | "user telephone is null"
        getUser(10005) || APIException      | "10005"         | "user sex is null"
        getUser(10006) || APIException      | "10006"         | "user order is null"
        getUser(10007) || APIException      | "10007"         | "order number is null"
        getUser(10008) || APIException      | "10008"         | "order amount is null"
    def getUser(errCode) {
        def user = new UserVO()
        def condition1 = {
            user.name = "杜兰特"
        def condition2 = {
            user.age = 20
        def condition3 = {
            user.telephone = "15801833812"
        def condition4 = {
            user.sex = "男"
        def condition5 = {
            user.userOrders = [new OrderVO()]
        def condition6 = {
            user.userOrders = [new OrderVO(orderNum: "123456")]
        switch (errCode) {
            case 10001:
                user = null
                break
            case 10002:
                user = new UserVO()
                break
            case 10003:
                condition1()
                break
            case 10004:
                condition1()
                condition2()
                break
            case 10005:
                condition1()
                condition2()
                condition3()
                break
            case 10006:
                condition1()
                condition2()
                condition3()
                condition4()
                break
            case 10007:
                condition1()
                condition2()
                condition3()
                condition4()
                condition5()
                break
            case 10008:
                condition1()
                condition2()
                condition3()
                condition4()
                condition5()