Checking Result for success or error in Tests

testableSwiftResult.swift

extension Result where Failure == ParseError {
    func checkError(messageIfNotError: String, type: ParseErrorType) {
        switch self {
        case .success(_):
            XCTFail(messageIfNotError)
        case let .failure(error):
            if error.type != type {
                XCTFail("Should have thrown \(type.rawValue) but did \(error.type)")
            }
        }
    }
    
    func checkSuccess(checker: ((Success) -> Void)) {
        switch self {
        case let .success(value):
            checker(value)
        case let .failure(error):
            XCTFail("Should have succeeded, but failed with \(error).")
        }
    }
}