Override dependencies in complex testing

[marcuswu0814]

I’m trying to refactor my dependencies system and fix my failing test cases, facing two problems, the executable demo project is here.

Question A - Mock a nested dependency in testing

According to Discussion #21, I made a nested dependencies with this pattern.

In my test case, I try to do partial mock, but it does not work as excepted.

final class QuestionA: XCTestCase {
    func test_notWork() {
        let sut = withDependencies {
            // $0.b = .init(dependentOnA: .init { "Mock" }) // this work but not live b
            $0.a = .init { "Mock" } // Not work
        } operation: {
            SomeClassUsingDependency()
        }

        XCTAssertEqual(sut.get(), "Mock") // Assert failed
    }
    func test() {
        let sut = withDependencies {
            $0.a = .init {
                "Mock"
            }
        } operation: {
            withDependencies { inner in
                inner.b = .liveValue
            } operation: {
                SomeClassUsingDependency()
            }
        }

        XCTAssertEqual(sut.get(), "Mock")
    }
}

If I need using live b implementation, and only mock my a service, what is the best practice to do this? Currently I use nested withDependencies(_:operation:) to do so. But it let test case much unreadable. Any suggestion for this situation?

Question B - Override dependencies after global mock

According to BaseTestCaseTests.swift and Documentation - Override Dependencies, I create a BaseTestCase and mock some dependency globally in all test cases.

When I trying to override it in some specific test case, it doesn’t work. Is this a supported feature?

class BaseTestCase: XCTestCase {
    override func invokeTest() {
        withDependencies {
            $0.c.child = .init {
                "Hello"
            }
        } operation: {
            super.invokeTest()
        }
    }
}

final class QuestionB: BaseTestCase {
    func test() {
        let sut = withDependencies {
            $0.c.child = .init {
                "World"
            }
        } operation: {
            SomeClassUsingServiceC()
        }

        // XCTAssertEqual(sut.get(), "World") // Failed
        XCTAssertEqual(sut.get(), "Hello")
    }
}