Test.swift

    func test(with identifier: String = #function, body: (XCTestExpectation) -> Void) {
        let expectation = expectation(description: identifier)
        body(expectation)
        waitForExpectations(timeout: 0.5)
    }
    
    func testAscending() {
        let a = [1]
        
        test { expectation in
            a.publisher.sink { value in
                XCTAssert(value == 2)
                expectation.fulfill()
            }.store(in: &cancellables)
        }
    }