AnyPublisher Test.swift

let expectedOutput = "Hello, World!"
let publisher = SomePublisher<String, Error>()

let cancellable = publisher
    .sink(receiveCompletion: { completion in
        switch completion {
        case .finished:
            break
        case .failure(let error):
            XCTFail("Publisher failed with error: \(error)")
        }
    }, receiveValue: { value in
        XCTAssertEqual(value, expectedOutput)
    })