在调用每个测试方法之前如何调用setUp（）方法？

I'm going through a great book learning about test-driven development in Swift. My ultimate goal is to get a better understanding of OOP architecture. As I'm reading the book, a section early on states that the setUp() method is fired before each test method which I understand does the setup of objects to run the test for a pass or fail result. What I'm unsure of is how is this even possible I'm guessing from an architecture stand-point? How was Apple able to make a class that has a method which is fired before every other method in the class?

我正在阅读一本关于Swift中测试驱动开发的好书。我的最终目标是更好地理解OOP架构。在我读这本书时，早期的一节说明在我理解的每个测试方法之前触发了setUp（）方法，对象的设置是为了通过或失败结果运行测试。我不确定的是，从架构的角度来看，这是怎么回事？ Apple如何能够创建一个具有在类中的每个其他方法之前触发的方法的类？

Here is some sample code:

以下是一些示例代码：

import XCTest
@testable import FirstDemo

class FirstDemoTests: XCTestCase {

    override func setUp() {
        super.setUp()
        // Put setup code here. This method is called before the invocation of each test method in the class.
    }

    override func tearDown() {
        // Put teardown code here. This method is called after the invocation of each test method in the class.
        super.tearDown()
    }

    func testExample() {
        // This is an example of a functional test case.
        // Use XCTAssert and related functions to verify your tests produce the correct results.
    }

    func testPerformanceExample() {
        // This is an example of a performance test case.
        self.measure {
            // Put the code you want to measure the time of here.
        }
    }

}

3 个解决方案

#1

I think XCTest class has a lifecycle just like UIViewController for example.

我认为XCTest类的生命周期就像UIViewController一样。

Same as viewDidLoad() called after init(coder:) when the view is loaded into memory, setUp() method is also called after the test class is loaded (once during the life of the object).

与init（coder :)之后调用的viewDidLoad（）相同，当视图加载到内存中时，setUp（）方法也会在加载测试类后调用（在对象的生命周期内一次）。

You can also investigate native and third party test frameworks source code on github:

您还可以在github上调查本机和第三方测试框架的源代码：

https://github.com/apple/swift-corelibs-xctest

https://github.com/apple/swift-corelibs-xctest

https://github.com/google/googletest

https://github.com/google/googletest

#2

You are Subclassing a Class called XCTestCase. Usally Testframework introspects Classes in which Test-Methods are defined and run them in a particular order.

您正在对一个名为XCTestCase的类进行子类化。通常，Testframework会内省定义测试方法的类，并按特定顺序运行它们。

Anyway, im not 100% sure if the XCTest is working this way, but you could try to have a look at the source code and try to dig deeper there:

无论如何，我不是100％确定XCTest是否以这种方式工作，但您可以尝试查看源代码并尝试深入挖掘：

https://github.com/apple/swift-corelibs-xctest

https://github.com/apple/swift-corelibs-xctest

#3

For each test to be tested: setup() is called, then the actual test, then teardown().

对于每个要测试的测试：调用setup（），然后调用实际测试，然后调用（）。

Then again setup another test from that class and tearDown again...until all** tests of your test class get ran.

然后再次从该类设置另一个测试并再次使用tearDown ...直到测试类的所有**测试都运行完毕。

_{The sequence of the lines won't affect which test gets called first.}

这些行的顺序不会影响首先调用哪个测试。

The reason that it's made this way is because 2 tests should be 100% independent. You don't want testExample do something to the object/sut/system_under_test (mutate its state) you're performing your tests on but, not undo what it's done. Otherwise your testPerformanceExample would be loaded from a state you weren't expecting.

之所以采用这种方式是因为2次测试应该是100％独立的。你不希望testExample对object / sut / system_under_test做一些事情（改变它的状态）你正在执行你的测试，但是不要撤消它做了什么。否则，您的testPerformanceExample将从您不期望的状态加载。