简单来说就是通过delegate的方式把处理XCTExpectation的方法解耦，可以在delegate回调中处理超时，中断等异步测试用例的异常，根据实际需求，决定是否让case 通过，或是抛出一个错误。
样例代码：
class WeiboModelTest : XCTestCase {
var model : WeiboModel?
let bag = DisposeBag()
let chinaCode = "001"
var waiter : XCTWaiter?
override func setUpWithError() throws {
self.model = WeiboModel()
self.waiter = XCTWaiter(delegate: self)
}
func testWaiter() {
let expectaton1:XCTestExpectation = expectation(description: "Fail1")
DispatchQueue.global().async {
Thread.sleep(forTimeInterval: 1)
expectaton1.fulfill()
}
expectaton1.isInverted = true
waiter?.wait(for: [expectaton1], timeout: 2)
}
func testWaiterSuccess() {
let expectaton1:XCTestExpectation = expectation(description: "Pass")
DispatchQueue.global().async {
Thread.sleep(forTimeInterval: 1)
expectaton1.fulfill()
}
waiter?.wait(for: [expectaton1], timeout: 0.5)
}
}
extension WeiboModelTest {
override func waiter(_ waiter: XCTWaiter, didFulfillInvertedExpectation expectation: XCTestExpectation) {
if (expectation.expectationDescription == "Fail") {
XCTFail(expectation.expectationDescription)
}
}
override func waiter(_ waiter: XCTWaiter, didTimeoutWithUnfulfilledExpectations unfulfilledExpectations: [XCTestExpectation]) {
if (unfulfilledExpectations[0].expectationDescription != "Pass") {
XCTFail(unfulfilledExpectations[0].expectationDescription)
}
}
}