Как реализовать unit test для fatalError кода в Swift?
Например, у меня есть следующий быстрый код
func divide(x: Float, by y: Float) -> Float {
guard y != 0 else {
fatalError("Zero division")
}
return x / y
}
Я хочу unit test случай, когда y = 0.
Примечание. Я хочу использовать fatalError, а не любую другую функцию утверждения.
Спасибо nschum и Кену Ко за идею этого ответа.
Вот суть того, как это сделать.
Этот ответ не только для фатальной ошибки. Это также для других методов утверждения (assert, assertionFailure, precondition, preconditionFailure и fatalError)
ProgrammerAssertions.swift на цель тестируемого приложения или фреймворка. Просто помимо вашего исходного кода.ProgrammerAssertions.swift
import Foundation
/// drop-in replacements
public func assert(@autoclosure condition: () -> Bool, @autoclosure _ message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
Assertions.assertClosure(condition(), message(), file, line)
}
public func assertionFailure(@autoclosure message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
Assertions.assertionFailureClosure(message(), file, line)
}
public func precondition(@autoclosure condition: () -> Bool, @autoclosure _ message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
Assertions.preconditionClosure(condition(), message(), file, line)
}
@noreturn public func preconditionFailure(@autoclosure message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
Assertions.preconditionFailureClosure(message(), file, line)
runForever()
}
@noreturn public func fatalError(@autoclosure message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
Assertions.fatalErrorClosure(message(), file, line)
runForever()
}
/// Stores custom assertions closures, by default it points to Swift functions. But test target can override them.
public class Assertions {
public static var assertClosure = swiftAssertClosure
public static var assertionFailureClosure = swiftAssertionFailureClosure
public static var preconditionClosure = swiftPreconditionClosure
public static var preconditionFailureClosure = swiftPreconditionFailureClosure
public static var fatalErrorClosure = swiftFatalErrorClosure
public static let swiftAssertClosure = { Swift.assert($0, $1, file: $2, line: $3) }
public static let swiftAssertionFailureClosure = { Swift.assertionFailure($0, file: $1, line: $2) }
public static let swiftPreconditionClosure = { Swift.precondition($0, $1, file: $2, line: $3) }
public static let swiftPreconditionFailureClosure = { Swift.preconditionFailure($0, file: $1, line: $2) }
public static let swiftFatalErrorClosure = { Swift.fatalError($0, file: $1, line: $2) }
}
/// This is a 'noreturn' function that runs forever and does not return.
/// Used by assertions with '@noreturn'.
@noreturn private func runForever() {
repeat {
NSRunLoop.currentRunLoop().run()
} while (true)
}
XCTestCase+ProgrammerAssertions.swift к вашей тестовой цели. Только помимо ваших тестовых случаев.XCTestCase + ProgrammerAssertions.swift
import Foundation
import XCTest
@testable import Assertions
private let noReturnFailureWaitTime = 0.1
public extension XCTestCase {
/**
Expects an 'assert' to be called with a false condition.
If 'assert' not called or the assert condition is true, the test case will fail.
- parameter expectedMessage: The expected message to be asserted to the one passed to the 'assert'. If nil, then ignored.
- parameter file: The file name that called the method.
- parameter line: The line number that called the method.
- parameter testCase: The test case to be executed that expected to fire the assertion method.
*/
public func expectAssert(
expectedMessage: String? = nil,
file: StaticString = __FILE__,
line: UInt = __LINE__,
testCase: () -> Void
) {
expectAssertionReturnFunction("assert", file: file, line: line, function: { (caller) -> () in
Assertions.assertClosure = { condition, message, _, _ in
caller(condition, message)
}
}, expectedMessage: expectedMessage, testCase: testCase) { () -> () in
Assertions.assertClosure = Assertions.swiftAssertClosure
}
}
/**
Expects an 'assertionFailure' to be called.
If 'assertionFailure' not called, the test case will fail.
- parameter expectedMessage: The expected message to be asserted to the one passed to the 'assertionFailure'. If nil, then ignored.
- parameter file: The file name that called the method.
- parameter line: The line number that called the method.
- parameter testCase: The test case to be executed that expected to fire the assertion method.
*/
public func expectAssertionFailure(
expectedMessage: String? = nil,
file: StaticString = __FILE__,
line: UInt = __LINE__,
testCase: () -> Void
) {
expectAssertionReturnFunction("assertionFailure", file: file, line: line, function: { (caller) -> () in
Assertions.assertionFailureClosure = { message, _, _ in
caller(false, message)
}
}, expectedMessage: expectedMessage, testCase: testCase) { () -> () in
Assertions.assertionFailureClosure = Assertions.swiftAssertionFailureClosure
}
}
/**
Expects an 'precondition' to be called with a false condition.
If 'precondition' not called or the precondition condition is true, the test case will fail.
- parameter expectedMessage: The expected message to be asserted to the one passed to the 'precondition'. If nil, then ignored.
- parameter file: The file name that called the method.
- parameter line: The line number that called the method.
- parameter testCase: The test case to be executed that expected to fire the assertion method.
*/
public func expectPrecondition(
expectedMessage: String? = nil,
file: StaticString = __FILE__,
line: UInt = __LINE__,
testCase: () -> Void
) {
expectAssertionReturnFunction("precondition", file: file, line: line, function: { (caller) -> () in
Assertions.preconditionClosure = { condition, message, _, _ in
caller(condition, message)
}
}, expectedMessage: expectedMessage, testCase: testCase) { () -> () in
Assertions.preconditionClosure = Assertions.swiftPreconditionClosure
}
}
/**
Expects an 'preconditionFailure' to be called.
If 'preconditionFailure' not called, the test case will fail.
- parameter expectedMessage: The expected message to be asserted to the one passed to the 'preconditionFailure'. If nil, then ignored.
- parameter file: The file name that called the method.
- parameter line: The line number that called the method.
- parameter testCase: The test case to be executed that expected to fire the assertion method.
*/
public func expectPreconditionFailure(
expectedMessage: String? = nil,
file: StaticString = __FILE__,
line: UInt = __LINE__,
testCase: () -> Void
) {
expectAssertionNoReturnFunction("preconditionFailure", file: file, line: line, function: { (caller) -> () in
Assertions.preconditionFailureClosure = { message, _, _ in
caller(message)
}
}, expectedMessage: expectedMessage, testCase: testCase) { () -> () in
Assertions.preconditionFailureClosure = Assertions.swiftPreconditionFailureClosure
}
}
/**
Expects an 'fatalError' to be called.
If 'fatalError' not called, the test case will fail.
- parameter expectedMessage: The expected message to be asserted to the one passed to the 'fatalError'. If nil, then ignored.
- parameter file: The file name that called the method.
- parameter line: The line number that called the method.
- parameter testCase: The test case to be executed that expected to fire the assertion method.
*/
public func expectFatalError(
expectedMessage: String? = nil,
file: StaticString = __FILE__,
line: UInt = __LINE__,
testCase: () -> Void) {
expectAssertionNoReturnFunction("fatalError", file: file, line: line, function: { (caller) -> () in
Assertions.fatalErrorClosure = { message, _, _ in
caller(message)
}
}, expectedMessage: expectedMessage, testCase: testCase) { () -> () in
Assertions.fatalErrorClosure = Assertions.swiftFatalErrorClosure
}
}
// MARK:- Private Methods
private func expectAssertionReturnFunction(
functionName: String,
file: StaticString,
line: UInt,
function: (caller: (Bool, String) -> Void) -> Void,
expectedMessage: String? = nil,
testCase: () -> Void,
cleanUp: () -> ()
) {
let expectation = expectationWithDescription(functionName + "-Expectation")
var assertion: (condition: Bool, message: String)? = nil
function { (condition, message) -> Void in
assertion = (condition, message)
expectation.fulfill()
}
// perform on the same thread since it will return
testCase()
waitForExpectationsWithTimeout(0) { _ in
defer {
// clean up
cleanUp()
}
guard let assertion = assertion else {
XCTFail(functionName + " is expected to be called.", file: file.stringValue, line: line)
return
}
XCTAssertFalse(assertion.condition, functionName + " condition expected to be false", file: file.stringValue, line: line)
if let expectedMessage = expectedMessage {
// assert only if not nil
XCTAssertEqual(assertion.message, expectedMessage, functionName + " called with incorrect message.", file: file.stringValue, line: line)
}
}
}
private func expectAssertionNoReturnFunction(
functionName: String,
file: StaticString,
line: UInt,
function: (caller: (String) -> Void) -> Void,
expectedMessage: String? = nil,
testCase: () -> Void,
cleanUp: () -> ()
) {
let expectation = expectationWithDescription(functionName + "-Expectation")
var assertionMessage: String? = nil
function { (message) -> Void in
assertionMessage = message
expectation.fulfill()
}
// act, perform on separate thead because a call to function runs forever
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), testCase)
waitForExpectationsWithTimeout(noReturnFailureWaitTime) { _ in
defer {
// clean up
cleanUp()
}
guard let assertionMessage = assertionMessage else {
XCTFail(functionName + " is expected to be called.", file: file.stringValue, line: line)
return
}
if let expectedMessage = expectedMessage {
// assert only if not nil
XCTAssertEqual(assertionMessage, expectedMessage, functionName + " called with incorrect message.", file: file.stringValue, line: line)
}
}
}
}
assert, assertionFailure, precondition, preconditionFailure и fatalError как обычно, как обычно.Например: если у вас есть функция, которая выполняет деление, подобное следующему:
func divideFatalError(x: Float, by y: Float) -> Float {
guard y != 0 else {
fatalError("Zero division")
}
return x / y
}
expectAssert, expectAssertionFailure, expectPrecondition, expectPreconditionFailure и expectFatalError.Вы можете проверить деление 0 с помощью следующего кода.
func testFatalCorrectMessage() {
expectFatalError("Zero division") {
divideFatalError(1, by: 0)
}
}
Или, если вы не хотите проверять сообщение, вы просто делаете это.
func testFatalErrorNoMessage() {
expectFatalError() {
divideFatalError(1, by: 0)
}
}
Идея состоит в том, чтобы заменить встроенную функцию fatalError на вашу собственную, которая заменяется во время выполнения unit test, так что вы запускаете в нем unit test утверждения.
Однако сложная часть состоит в том, что fatalError - @noreturn, поэтому вам нужно переопределить ее с помощью функции, которая никогда не возвращается.
Только в вашей целевой программе (не добавляйте к цели unit test):
// overrides Swift global `fatalError`
@noreturn func fatalError(@autoclosure message: () -> String = "", file: StaticString = __FILE__, line: UInt = __LINE__) {
FatalErrorUtil.fatalErrorClosure(message(), file, line)
unreachable()
}
/// This is a `noreturn` function that pauses forever
@noreturn func unreachable() {
repeat {
NSRunLoop.currentRunLoop().run()
} while (true)
}
/// Utility functions that can replace and restore the `fatalError` global function.
struct FatalErrorUtil {
// Called by the custom implementation of `fatalError`.
static var fatalErrorClosure: (String, StaticString, UInt) -> () = defaultFatalErrorClosure
// backup of the original Swift `fatalError`
private static let defaultFatalErrorClosure = { Swift.fatalError($0, file: $1, line: $2) }
/// Replace the `fatalError` global function with something else.
static func replaceFatalError(closure: (String, StaticString, UInt) -> ()) {
fatalErrorClosure = closure
}
/// Restore the `fatalError` global function back to the original Swift implementation
static func restoreFatalError() {
fatalErrorClosure = defaultFatalErrorClosure
}
}
Добавьте в свой unit test объект следующего расширения:
extension XCTestCase {
func expectFatalError(expectedMessage: String, testcase: () -> Void) {
// arrange
let expectation = expectationWithDescription("expectingFatalError")
var assertionMessage: String? = nil
// override fatalError. This will pause forever when fatalError is called.
FatalErrorUtil.replaceFatalError { message, _, _ in
assertionMessage = message
expectation.fulfill()
}
// act, perform on separate thead because a call to fatalError pauses forever
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), testcase)
waitForExpectationsWithTimeout(0.1) { _ in
// assert
XCTAssertEqual(assertionMessage, expectedMessage)
// clean up
FatalErrorUtil.restoreFatalError()
}
}
}
class TestCase: XCTestCase {
func testExpectPreconditionFailure() {
expectFatalError("boom!") {
doSomethingThatCallsFatalError()
}
}
}
У меня появилась идея из этого сообщения об модульном тестировании assert и precondition:
Тестирование утверждения в Swift
На основании ответа Кена.
В приложении App Target добавьте следующее:
import Foundation
// overrides Swift global `fatalError`
public func fatalError(_ message: @autoclosure () -> String = "", file: StaticString = #file, line: UInt = #line) -> Never {
FatalErrorUtil.fatalErrorClosure(message(), file, line)
unreachable()
}
/// This is a `noreturn` function that pauses forever
public func unreachable() -> Never {
repeat {
RunLoop.current.run()
} while (true)
}
/// Utility functions that can replace and restore the `fatalError` global function.
public struct FatalErrorUtil {
// Called by the custom implementation of `fatalError`.
static var fatalErrorClosure: (String, StaticString, UInt) -> Never = defaultFatalErrorClosure
// backup of the original Swift `fatalError`
private static let defaultFatalErrorClosure = { Swift.fatalError($0, file: $1, line: $2) }
/// Replace the `fatalError` global function with something else.
public static func replaceFatalError(closure: @escaping (String, StaticString, UInt) -> Never) {
fatalErrorClosure = closure
}
/// Restore the `fatalError` global function back to the original Swift implementation
public static func restoreFatalError() {
fatalErrorClosure = defaultFatalErrorClosure
}
}
В тестовой цели добавьте следующее:
import Foundation
import XCTest
extension XCTestCase {
func expectFatalError(expectedMessage: String, testcase: @escaping () -> Void) {
// arrange
let expectation = self.expectation(description: "expectingFatalError")
var assertionMessage: String? = nil
// override fatalError. This will pause forever when fatalError is called.
FatalErrorUtil.replaceFatalError { message, _, _ in
assertionMessage = message
expectation.fulfill()
unreachable()
}
// act, perform on separate thead because a call to fatalError pauses forever
DispatchQueue.global(qos: .userInitiated).async(execute: testcase)
waitForExpectations(timeout: 0.1) { _ in
// assert
XCTAssertEqual(assertionMessage, expectedMessage)
// clean up
FatalErrorUtil.restoreFatalError()
}
}
}
Тестовый случай:
class TestCase: XCTestCase {
func testExpectPreconditionFailure() {
expectFatalError(expectedMessage: "boom!") {
doSomethingThatCallsFatalError()
}
}
}