Workaround for XCTest not reporting failing NSAssertions.

gistfile1.txt

#import "PWAssertionHandler.h"
#import "PWLog.h"
#import "Intercept_objc_exception_throw.h"
#import <objc/runtime.h>
#import "PWDispatch.h"

#ifndef NDEBUG

@interface NSAssertionHandler (PWExtensions)
@property (nonatomic, readonly) BOOL isPWHandler;
@end

#pragma mark -

@implementation NSAssertionHandler (PWExtensions)

// The load method of any class could be used to install our intercept whenever PWFoundation is loaded.
+ (void) load
{
    intercept_objc_exception_throw();
    [self patchCurrentHandler];
}

+ (NSAssertionHandler*) patched_currentHandler
{
    // this is not a recursion because of exchanged implementations
    NSAssertionHandler* handler = [self patched_currentHandler];
    
    // Create and install our handler on each thread for which it is requested.
    if (!handler.isPWHandler) {
        handler = [[PWAssertionHandler alloc] init];
        NSThread.currentThread.threadDictionary[NSAssertionHandlerKey] = handler;
    }
    return handler;
}

+ (void) patchCurrentHandler
{
    Method original = class_getClassMethod (self, @selector(currentHandler));
    NSAssert (original, nil);
    Method patched  = class_getClassMethod (self, @selector(patched_currentHandler));
    NSAssert (patched, nil);
    method_exchangeImplementations (original, patched);
}

- (BOOL) isPWHandler
{
    return NO;
}

@end

#pragma mark -

@implementation PWAssertionHandler
{
    BOOL    dontThrow_;
}

- (BOOL) isPWHandler
{
    return YES;
}

- (void) handleFailureInMethod:(SEL)selector
                        object:(id)object
                          file:(NSString*)fileName
                    lineNumber:(NSInteger)line
                   description:(NSString*)format,...
{
    NSString* description;
    if (format) {
        va_list argList;
        va_start (argList, format);
        description = [[NSString alloc] initWithFormat:format arguments:argList];
        va_end (argList);
    }
    
    Class objectClass = object_getClass (object);
    BOOL isClassMethod = class_isMetaClass (objectClass);

    [self logFakeTestCaseAroundBlock:^{
        PWLog (@"*** %@ in %c[%@ %@], %@:%li\n",
               description ? description : @"Assertion failure",
               isClassMethod ? '+' : '-', isClassMethod ? object : objectClass, NSStringFromSelector (selector),
               fileName, line);
    }];
    [self raiseExceptionWithDescription:description];
}

- (void) handleFailureInFunction:(NSString*)functionName
                            file:(NSString*)fileName
                      lineNumber:(NSInteger)line
                     description:(NSString*)format,...
{
    NSString* description;
    if (format) {
        va_list argList;
        va_start (argList, format);
        description = [[NSString alloc] initWithFormat:format arguments:argList];
        va_end (argList);
    }

    [self logFakeTestCaseAroundBlock:^{
        PWLog (@"*** %@ in %@, %@:%li\n",
               description ? description : @"Assertion failure",
               functionName, fileName, line);
    }];
    [self raiseExceptionWithDescription:description];
}

- (void) raiseExceptionWithDescription:(NSString*)description
{
    // To support moving the programm counter behind the throw in the debugger, the throw must not be the only possible
    // exit of the method. So far this is the only reason for dontThrow_.
    if (!dontThrow_) {
        PWAssertionException* exception = [[PWAssertionException alloc] initWithReason:description userInfo:nil];
        // Very important: under -fobjc-arc-exceptions -[NSException raise] does not work, the exception object is
        // released and deallocated before being thrown (probably by the exception cleanup code).
        // The class raise-methods are not affected: with them ARC never sees the exception object.
        // Speculation: when seeing @throw the compiler knows what happens and does the right thing.
        
        // Set a breakpoint on this statement to intercept ASSERTs before the exception is thrown. Can even move the
        // programm counter to the end of the method to continue without throwing.
        @throw exception;
    }
}

// When an exception occurs outside of the synchronous performing of a XCTestCase (even during -setup or -tearDown)
// the performing of the test suite is aborted without any report of a failed test.
// To avoid missing such a situation in continous integration tools,
// we simulated the output of a failed test case containig the exception description.
- (void)logFakeTestCaseAroundBlock:(PWDispatchBlock)block
{
    NSParameterAssert(block);
    if(NSClassFromString(@"XCTestCase"))
    {
        printf("%s", [[NSString stringWithFormat:@"Test Suite 'PWAssertionHandlerTests' started at %@\n", [NSDate date]] UTF8String]);
        printf("Test Case '-[PWAssertionHandler testAssertionFailed]' started.\n");
        printf("PWAssertionHandler.m:1: error: -[PWAssertionHandler testAssertionFailed] : ");
        block();
        printf("Test Case '-[PWAssertionHandler testAssertionFailed]' failed (0.000 seconds).\n");
        printf("%s", [[NSString stringWithFormat:@"Test Suite 'PWAssertionHandlerTests' finished at %@\n", [NSDate date]] UTF8String]);
    }
    else
        block();
}

@end