如何为下述Groovy代码编写shouldFail与ShouldPass测试用例？

以下基于Spock框架编写测试用例，覆盖withLocal方法的成功与失败场景：

成功场景（ShouldPass） #

当环境变量CREDENTIALS_ID设置有效值时，方法正常执行，无异常抛出，且输出对应凭证ID。

def "withLocal executes successfully when CREDENTIALS_ID is set"() {
    given:
    // 模拟环境变量存在有效值
    env.CREDENTIALS_ID = "prod-cred-456"
    def capturedEcho = []
    // 替换echo方法捕获输出内容
    def testTarget = new Expando(
        echo: { message -> capturedEcho.add(message) }
    )

    when:
    testTarget.withLocal {}

    then:
    // 验证输出内容匹配
    capturedEcho.first() == "credentials Id=prod-cred-456"
    // 确认无异常抛出
    noExceptionThrown()
}

失败场景（ShouldFail） #

当环境变量CREDENTIALS_ID未设置或为空时，方法抛出指定异常。

def "withLocal throws exception when CREDENTIALS_ID is null"() {
    given:
    // 模拟环境变量未设置
    env.CREDENTIALS_ID = null
    def testTarget = new Expando(
        echo: { message -> }
    )

    when:
    testTarget.withLocal {}

    then:
    // 验证异常类型与信息
    Exception thrownException = thrown()
    thrownException.message == "credentials not setup - env.CREDENTIALS_ID"
}

def "withLocal throws exception when CREDENTIALS_ID is empty string"() {
    given:
    // 模拟环境变量为空字符串
    env.CREDENTIALS_ID = ""
    def testTarget = new Expando(
        echo: { message -> }
    )

    when:
    testTarget.withLocal {}

    then:
    Exception thrownException = thrown()
    thrownException.message == "credentials not setup - env.CREDENTIALS_ID"
}

内容的提问来源于stack exchange，提问作者Aryan