ReadableTest

Background: Expressing Outcomes Using Assertions in XCTest

Testing Combine's Publisher only with XCTest would be a very complex description.

For example, XCTest has you write:

// SUT
class ItemListViewModel: ObservableObject {
    @Published var items = [String]()
    
    func addItem(_ item: String) {
        items.append(item)
    }
}

// Test
class ItemListViewModelTests: XCTestCase {
    var cancellables = Set<AnyCancellable>()
    
    func test_after_adding_apple__ViewModel_publishes_new_array_with_appleadded() {
        let viewModel = ItemListViewModel()
        
        
        viewModel.addItem("apple")
        
        
        let expectation = XCTestExpectation()
        viewModel.$items
            .dropFirst()
            .sink { newItems in
                XCTAssertEqual(newItems, ["apple"])
                expectation.fulfill()
            }
            .store(in: &cancellables)
        wait(for: [expectation])
    }
}

Testing Combine's Publisher only with XCTest have a couple of drawbacks:

1. Since we are testing the Publisher, of course we need to subscribe to it.
2. To avoid freeing memory immediately, it must be stored in a set of AnyCancellable defined outside the function
3. Since it is an asynchronous test, we have to instantiate XCTestExpectation and wait for the fullfill() to be executed

ReadableTest addresses these drowbacks.

Testing with ReadableTest

ReadableTest allows you to express expectations more easier or read expectations more instantly.

//SUT
class ItemListViewModel: ObservableObject {
    @Published var items = [String]()
    
    func addItem(_ item: String) {
        items.append(item)
    }
}

//Test
import ReadableTest

class ItemListViewModelTests: ReadableTestCase {
    func test_after_adding_apple__ViewModel_publishes_new_array_with_apple_added() {
        let viewModel = ItemListViewModel()
        
        
        viewModel.addItem("apple")
        
        
        expect(viewModel.$items).on(publication: 1).toEqual(["apple"])
    }
}

IMPORTANT: ReadableTest is a work in progress and does not support all aspects of testing. Features will be added as needed. If you see a feature you need, please please feel free to open an issue or make a PR.👍

License

ReadableTest is released under the MIT License, Please see the LICENSE.