[英]Unit Test fatalError in Swift
How to implement unit test for a fatalError
code path in Swift?如何在Swift中为
fatalError
代码路径实现单元测试?
For example, I've the following swift code例如,我有以下快速代码
func divide(x: Float, by y: Float) -> Float {
guard y != 0 else {
fatalError("Zero division")
}
return x / y
}
I want to unit test the case when y = 0.我想在 y = 0 时对案例进行单元测试。
Note, I want to use fatalError not any other assertion function.注意,我想使用 fatalError 而不是任何其他断言函数。
The idea is to replace the built-in fatalError
function with your own, which is replaced during a unit test's execution, so that you run unit test assertions in it.这个想法是用你自己的来替换内置的
fatalError
函数,它在单元测试的执行过程中被替换,这样你就可以在其中运行单元测试断言。
However, the tricky part is that fatalError
is @noreturn
, so you need to override it with a function which never returns.然而,棘手的部分是
fatalError
是@noreturn
,所以你需要用一个永远不会返回的函数来覆盖它。
In your app target only (don't add to the unit test target):仅在您的应用程序目标中(不要添加到单元测试目标):
// 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
}
}
Add the following extension to your unit test target:将以下扩展添加到您的单元测试目标:
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()
}
}
}
I got the idea from this post about unit testing assert
and precondition
: Testing assertion in Swift我从这篇关于单元测试
assert
和precondition
帖子中得到了想法: 在 Swift 中测试断言
Based on Ken's answer.基于肯的回答。
In your App Target add the following:在您的 App Target 中添加以下内容:
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
}
}
In your test target add the following:在您的测试目标中添加以下内容:
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()
}
}
}
Test case:测试用例:
class TestCase: XCTestCase {
func testExpectPreconditionFailure() {
expectFatalError(expectedMessage: "boom!") {
doSomethingThatCallsFatalError()
}
}
}
Thanks to nschum and Ken Ko for the idea behind this answer.感谢nschum和Ken Ko在这个答案背后的想法。
Here is a gist for how to do it.这是如何做到这一点的要点。
Here is an example project.这是一个示例项目。
This answer is not just for fatal error.这个答案不仅仅针对致命错误。 It's also for the other assertion methods (
assert
, assertionFailure
, precondition
, preconditionFailure
and fatalError
)它也适用于其他断言方法(
assert
、 assertionFailure
、 precondition
、 preconditionFailure
和fatalError
)
ProgrammerAssertions.swift
to the target of your app or framework under test. ProgrammerAssertions.swift
拖放到被测应用程序或框架的目标。 Just besides your source code. ProgrammerAssertions.swift 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 doesn't return.
/// Used by assertions with `@noreturn`.
@noreturn private func runForever() {
repeat {
NSRunLoop.currentRunLoop().run()
} while (true)
}
XCTestCase+ProgrammerAssertions.swift
to your test target. XCTestCase+ProgrammerAssertions.swift
放到你的测试目标。 Just besides your test cases. XCTestCase+ProgrammerAssertions.swift 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's 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's 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
and fatalError
normally as you always do. assert
、 assertionFailure
、 precondition
、 preconditionFailure
和fatalError
。 For example: If you have a function that does a division like the following:例如:如果您有一个执行如下除法的函数:
func divideFatalError(x: Float, by y: Float) -> Float {
guard y != 0 else {
fatalError("Zero division")
}
return x / y
}
expectAssert
, expectAssertionFailure
, expectPrecondition
, expectPreconditionFailure
and expectFatalError
. expectAssert
、 expectAssertionFailure
、 expectPrecondition
、 expectPreconditionFailure
和expectFatalError
对它们进行单元测试。 You can test the 0 division with the following code.您可以使用以下代码测试 0 除法。
func testFatalCorrectMessage() {
expectFatalError("Zero division") {
divideFatalError(1, by: 0)
}
}
Or if you don't want to test the message, you simply do.或者,如果您不想测试该消息,只需进行即可。
func testFatalErrorNoMessage() {
expectFatalError() {
divideFatalError(1, by: 0)
}
}
Nimble ("A Matcher Framework for Swift and Objective-C") got your back : Nimble (“Swift 和 Objective-C 的匹配框架”)支持您:
Swift Assertions
快速断言
If you're using Swift, you can use the throwAssertion matcher to check if an assertion is thrown (eg fatalError()).
如果您使用 Swift,您可以使用 throwAssertion 匹配器来检查是否抛出了断言(例如fatalError())。 This is made possible by @mattgallagher's CwlPreconditionTesting library.
@mattgallagher 的 CwlPreconditionTesting 库使这成为可能。
// Swift
// Passes if 'somethingThatThrows()' throws an assertion,
// such as by calling 'fatalError()' or if a precondition fails:
expect { try somethingThatThrows() }.to(throwAssertion())
expect { () -> Void in fatalError() }.to(throwAssertion())
expect { precondition(false) }.to(throwAssertion())
// Passes if throwing an NSError is not equal to throwing an assertion:
expect { throw NSError(domain: "test", code: 0, userInfo: nil) }.toNot(throwAssertion())
// Passes if the code after the precondition check is not run:
var reachedPoint1 = false
var reachedPoint2 = false
expect {
reachedPoint1 = true
precondition(false, "condition message")
reachedPoint2 = true
}.to(throwAssertion())
expect(reachedPoint1) == true
expect(reachedPoint2) == false
Notes:
笔记:
- This feature is only available in Swift.
此功能仅在 Swift 中可用。
- It is only supported for x86_64 binaries, meaning you cannot run this matcher on iOS devices, only simulators.
它仅支持 x86_64 二进制文件,这意味着您不能在 iOS 设备上运行此匹配器,只能在模拟器上运行。
- The tvOS simulator is supported, but using a different mechanism, requiring you to turn off the Debug executable scheme setting for your tvOS scheme's Test configuration.
支持 tvOS 模拟器,但使用不同的机制,需要您关闭 tvOS 方案的测试配置的调试可执行方案设置。
SWIFT 5, 4斯威夫特 5、4
This version not leaves a discarded thread in GCD for each call to expectFatalError.这个版本不会在每次调用 expectFatalError 时在 GCD 中留下一个被丢弃的线程。 This fixed by using a Thread rather than DispatchQueue.
这通过使用线程而不是 DispatchQueue 来解决。 Thanks to @jedwidz
感谢@jedwidz
import Foundation
// overrides Swift global `fatalError`
func fatalError(_ message: @autoclosure () -> String = String(), file: StaticString = #file, line: UInt = #line) -> Never {
FatalErrorUtil.fatalErrorClosure(message(), file, line)
}
/// Utility functions that can replace and restore the `fatalError` global function.
enum FatalErrorUtil {
typealias FatalErrorClosureType = (String, StaticString, UInt) -> Never
// Called by the custom implementation of `fatalError`.
static var fatalErrorClosure: FatalErrorClosureType = defaultFatalErrorClosure
// backup of the original Swift `fatalError`
private static let defaultFatalErrorClosure: FatalErrorClosureType = { Swift.fatalError($0, file: $1, line: $2) }
/// Replace the `fatalError` global function with something else.
static func replaceFatalError(closure: @escaping FatalErrorClosureType) {
fatalErrorClosure = closure
}
/// Restore the `fatalError` global function back to the original Swift implementation
static func restoreFatalError() {
fatalErrorClosure = defaultFatalErrorClosure
}
}
import XCTest
@testable import TargetName
extension XCTestCase {
func expectFatalError(expectedMessage: String, testcase: @escaping () -> Void) {
// arrange
let expectation = self.expectation(description: "expectingFatalError")
var assertionMessage: String? = nil
// override fatalError. This will terminate thread when fatalError is called.
FatalErrorUtil.replaceFatalError { message, _, _ in
assertionMessage = message
expectation.fulfill()
// Terminate the current thread after expectation fulfill
Thread.exit()
// Since current thread was terminated this code never be executed
fatalError("It will never be executed")
}
// act, perform on separate thread to be able terminate this thread after expectation fulfill
Thread(block: testcase).start()
waitForExpectations(timeout: 0.1) { _ in
// assert
XCTAssertEqual(assertionMessage, expectedMessage)
// clean up
FatalErrorUtil.restoreFatalError()
}
}
}
class TestCase: XCTestCase {
func testExpectPreconditionFailure() {
expectFatalError(expectedMessage: "boom!") {
doSomethingThatCallsFatalError()
}
}
}
Well, I figured I would upload some code for everyone that allowed XCTest to work with asserts and check here to see if anyone needed.好吧,我想我会为每个人上传一些允许 XCTest 使用断言的代码,并在此处查看是否有人需要。 Looks like the solutions here are remarkably similar to the one that I came up with.
看起来这里的解决方案与我提出的解决方案非常相似。 Great minds eh?
脑洞很大吧? :)
:)
Anyway, if anyone needs it or is curious, here is what I did.无论如何,如果有人需要它或好奇,这就是我所做的。
https://bitbucket.org/jasonbobier/xctest-additions/src/main/https://bitbucket.org/jasonbobier/xctest-additions/src/main/
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