Ios 为什么在我使用时单元测试覆盖率数据会发生变化？？（空合并运算符）？

我已经创建了一个雇员模型，其中id和name是可选属性，description方法将返回一个插值字符串

代码如下：

class Employee: NSObject {
    var id: String?
    var name: String?

    init(id: String, name: String) {
        self.id = id
        self.name = name
    }

    func description() -> String {
        return "Employee ID: \(id ?? "") and Employee Name: \(name ?? "")."
        //return "Employee ID: \(id != nil ? id! : "") and Employee Name: \(name ?? "")."
    }
}

class EmployeeTests: 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 testEmployee() {
        let employee = Employee(id: "1", name: "Yash Vyas")
        XCTAssertEqual(employee.id, "1")
        XCTAssertEqual(employee.name, "Yash Vyas")
        XCTAssertEqual(employee.description(), "Employee ID: 1 and Employee Name: Yash Vyas.")
    }
}

我已经为单元测试这个员工模型编写了测试用例

代码如下：

class Employee: NSObject {
    var id: String?
    var name: String?

    init(id: String, name: String) {
        self.id = id
        self.name = name
    }

    func description() -> String {
        return "Employee ID: \(id ?? "") and Employee Name: \(name ?? "")."
        //return "Employee ID: \(id != nil ? id! : "") and Employee Name: \(name ?? "")."
    }
}

class EmployeeTests: 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 testEmployee() {
        let employee = Employee(id: "1", name: "Yash Vyas")
        XCTAssertEqual(employee.id, "1")
        XCTAssertEqual(employee.name, "Yash Vyas")
        XCTAssertEqual(employee.description(), "Employee ID: 1 and Employee Name: Yash Vyas.")
    }
}

---

当我使用三元运算符而不是？？（description方法中的注释行）用于在从description（）方法返回插值字符串时检查nil的可选属性，以及在使用时为什么会减少？？（空合并）运算符。

添加另一个这样的情况可以解决问题：

let another = Employee(id: "1", name: "Yash Vyas")
another.id = nil
XCTAssertEqual(another.description(), "Employee ID:  and Employee Name: Yash Vyas.")

虽然在我看来，这可能是llvm或Xcode端的一个bug