自定义启动指标未报告预期结果

Question

我想“访问”

XCTApplicationLaunchMetric

中报告的测量结果。为此，我创建了自己的类，它采用

XCTMetric

并在幕后使用、调用

XCTApplicationLaunchMetric

，如下所示：

class MyXCTApplicationLaunchMetric: NSObject, XCTMetric {
    let myLaunchMetric: XCTApplicationLaunchMetric

    init(waitUntilResponsive: Bool) {
        print(#function)
        myLaunchMetric = XCTApplicationLaunchMetric(waitUntilResponsive: waitUntilResponsive)
    }

    // XCTMetric conformance
    func willBeginMeasuring() {
        print(#function)
        myLaunchMetric.willBeginMeasuring()
    }

    // XCTMetric conformance
    func didStopMeasuring() {
        print(#function)
        myLaunchMetric.didStopMeasuring()
    }

    // XCTMetric conformance
    func reportMeasurements(from startTime: XCTPerformanceMeasurementTimestamp, to endTime: XCTPerformanceMeasurementTimestamp) throws -> [XCTPerformanceMeasurement] {
        let measurement = Measurement(value: 40, unit: .init(symbol: "M"))
        let performanceMeasurement = XCTPerformanceMeasurement(identifier: "SomeIdentifier", displayName: "SomeDisplayName", value: measurement)
        return [performanceMeasurement]
    }

    // NSObject conformance
    func copy(with zone: NSZone? = nil) -> Any {
        myLaunchMetric.copy(with: zone)
    }
}

但是，当我在这里使用它时，没有调用任何

XCTMetric

函数。称为

init

。我不知道为什么。

final class PerformanceUITests: XCTestCase {
    func testLaunchPerformance() throws {
        if #available(macOS 10.15, iOS 13.0, tvOS 13.0, watchOS 7.0, *) {
            let options = XCTMeasureOptions()
            options.iterationCount = 1

            let launchMetric = MyXCTApplicationLaunchMetric(waitUntilResponsive: true)
            measure(metrics: [launchMetric],
                    options: options) {
                XCUIApplication().launch()
            }
        }
    }
}

Answer 1

原因是因为

measure

调用

copy(with:)

并且您不是返回自定义类型的实例，而是

myLaunchMetric

这是

XCTApplicationLaunchMetric

的实例。