如何在 Swift 中对投掷函数进行单元测试？

编辑:将代码更新为Swift 4.1(对Swift 5.2仍然有效)

以下是使用XCTAssertThrowsError的Fyodor Volchyok's answer的最新Swift版本:

    enum MyError: Error {
        case someExpectedError
        case someUnexpectedError
    }

    func functionThatThrows() throws {
        throw MyError.someExpectedError
    }

    func testFunctionThatThrows() {
        XCTAssertThrowsError(try functionThatThrows()) { error in
            XCTAssertEqual(error as! MyError, MyError.someExpectedError)
        }
    }

如果Error enum具有关联值，则可以让Error enum符合Equatable，或使用if case语句:

    enum MyError: Error, Equatable {
        case someExpectedError
        case someUnexpectedError
        case associatedValueError(value: Int)
    }

    func functionThatThrows() throws {
        throw MyError.associatedValueError(value: 10)
    }

    // Equatable pattern: simplest solution if you have a simple associated value that can be tested inside 1 XCTAssertEqual
    func testFunctionThatThrows() {
        XCTAssertThrowsError(try functionThatThrows()) { error in
            XCTAssertEqual(error as! MyError, MyError.associatedValueError(value: 10))
        }
    }

    // if case pattern: useful if you have one or more associated values more or less complex (struct, classes...)
    func testFunctionThatThrows() {
        XCTAssertThrowsError(try functionThatThrows()) { error in
            guard case MyError.associatedValueError(let value) = error else {
                return XCTFail()
            }

            XCTAssertEqual(value, 10)
            // if you have several values or if they require more complex tests, you can do it here
        }
    }