norio-nomura/xctassertcrash

Usage

/// Asserts that an expression crashes.
/// - Parameters:
///     - expression: An `expression` that can crash.
///     - message: An optional description of the failure.
///     - file: The file in which failure occurred.
///             Defaults to the file name of the test case in which this function was called.
///     - line: The line number on which failure occurred.
///             Defaults to the line number on which this function was called.
///     - signalHandler: An optional handler for signal that are produced by `expression`.
///                      `SIGILL`, `SIGABRT` or `0` (if `expression` did not crash)
///     - stdoutHandler: An optional handler for stdout that are produced by `expression`.
///     - stderrHandler: An optional handler for stderr that are produced by `expression`.
///     - skipIfBeingDebugged: Skip `expression` if process is being debugged.
///                            Use `skipXCTAssertCrashIfIsBeingDebugged` as default.
/// - Returns: A value of type `T?`, the result of evaluating the given `expression`.
///            `nil` if `expression` crashed.
@discardableResult
public func XCTAssertCrash<T>(
    _ expression: @escaping @autoclosure () -> T,
    _ message: @autoclosure () -> String = "",
    file: StaticString = #file,
    line: UInt = #line,
    signalHandler: (Int32) -> Void = { _ in },
    stdoutHandler: (String) -> Void = { _ in },
    stderrHandler: (String) -> Void = { _ in },
    skipIfBeingDebugged: Bool = skipXCTAssertCrashIfIsBeingDebugged
) -> T?

Limitations

Mach Exception Handler

• XCTAssertCrash can not handle crashes caused by abort().
• XCTAssertCrash can not handle a breakpoint set in expression. On detecting a stop at a breakpoint set by the debugger, XCTAssertCrash generates assertionFailure().

POSIX Signal Handler

• lldb will catch the signal and stop on crash before XCTAssertCrash detects it.
• So, if the process is being debugged, XCTAssertCrash will skip the evaluation of the expression by default.

To avoid this behavior, - Set skipXCTAssertCrashIfIsBeingDebugged to false. or - Disable debug. e.g. In Xcode, go to 'Edit Scheme > Test > Info' and uncheck 'Debug Executable'.

Author

Norio Nomura

License

This package is available under the MIT license. See the LICENSE file for more info.

References

• Partial functions in Swift, Part 2: Catching precondition failures by Matt Gallagher
• Friday Q&A 2013-01-11: Mach Exception Handlers by Landon Fuller
• Mac OS X and iOS Internals by Jonathan Levin
• The Darwin Kernel by Apple

Package Metadata

Repository: norio-nomura/xctassertcrash

Default branch: master

README: README.md