匹配数组元素的测试用例-Quick and Nimble Swift

Question

如何使用Quick and Nimble编写测试用例以检查这段代码？

在ViewController中

for id in boxesArray {
    if let box = Boxservice.shared.storeBoxes.size(id: id), box.size != nil {
         availbleBoxesArray.append(box.size)
    }
}

在测试用例文件中

context("When boxes array is not nil") {
 let box = BoxSize()
 box.size = "medium"

 let storeBoxes = StoreBoxes.init()
 storeBoxes.add(box)

beforeEach {
  Boxservice.shared.storeBoxes = storeBoxes
  viewController.fetchBoxSizes()
}

it("available boxes should not be nil") {
  expect(viewController?.availbleBoxesArray).toNot(beNil()) // This test passes succesfully.
}

it("available boxes should contain given box size") {
  expect(viewController?.availbleBoxesArray.first).to(contain(box)) // This test is failing.
}
}

代码覆盖率并未覆盖该代码段的顶部，并且无法快速，灵活地测试该部分。如何编写适当的测试用例以处理该用例。

非常感谢您的帮助。