Thanks for the report, @drewcrawford! I'm a little confused, though--why do you think XCTLog should be defined? I'm not familiar with that function, and looking through swift-corelibs-xctest, we don't appear to define it anywhere. Apple XCTest doesn't document it in any of its public headers, either.

Apple XCTest does define a class XCTestLog:

#import <XCTest/XCTestObserver.h>

/*!
 * XCTestLog is deprecated.
 */

DEPRECATED_ATTRIBUTE
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wdeprecated-declarations"
@interface XCTestLog : XCTestObserver
#pragma clang diagnostic pop

@property (readonly, strong) NSFileHandle *logFileHandle;
- (void)testLogWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);
- (void)testLogWithFormat:(NSString *)format arguments:(va_list)arguments NS_FORMAT_FUNCTION(1,0);

@end

Note that XCTestLog is deprecated.

In any case, could you explain what the bug is here? Sorry for not catching on!

Sorry for writing a trainwreck of a bug report. Let me explain how I got here:

1. print didn't work inside an XCTest target, on x64 Linux. Is that a bug? Well, maybe not... I know XCTest does weird XPC stuff on Darwin, maybe stdout isn't connected on Linux by design.
2. Typed in XCT and waited for autocomplete, oh look! XCTLog XCTestLog sounds like a log mechanism. Guess I should use this.
3. But not on Linux, because it's not implemented.
4. Begrudingly use fputs("(whatever)\n",stderr) everywhere, take a shot, file a bug.

Knowing what I know now:

1. Maybe the real bug is that print doesn't work?
2. Maybe the real bug is that there's no documentation that would tell me whether print is supposed to work or not?
3. Maybe the real bug is that we don't ship a logging function that works instead?
4. Maybe there's an Xcode bug in here that doesn't sound an alarm when I try to use a deprecated symbol?


I know that I still haven't given enough information to get any of these issues reproducible, but it would be a good start to find out which ones are expected and which are not.

Aha, thanks for the detailed follow-up! 🙂

print() should most certainly work from within an XCTestCase method... I wonder what's going on here. Can you describe what you mean by "not work"? Is it not being output? Are you sure the test method is being executed? Is the method included in your allTests list?

Ping @drewcrawford--did you see my comment above? Does this still happen for you?

Sorry @modocache. I decided to reply by rewriting the bug description, since my original was so bad, and was a poor introduction to anyone who might stumble onto the issue. I thought it would notify you. It seems it did not.

I am still affected by the issue. The rewritten bug description includes a full test case.

Thanks for following up.

The root cause of this may be https://bugs.swift.org/browse/SR-1127. Based on the comment by Dmitri there, we may want to close this as a "won't fix".

@drewcrawford Could you follow-up on whether this is still affecting you, and whether you think that the `print()` buffering could be the source? Does the missing output appear if you explicitly flush before the `fatalError`? I'll point out that XCTest itself does explicitly flush after each of its `print` statements: https://github.com/apple/swift-corelibs-xctest/blob/master/Sources/XCTest/PrintObserver.swift#L69

I'm going to go ahead and close this due to:

1. The fact that it's probably no longer a problem for the original reporter

2. "Fixing" the print() behavior is a much larger problem that is better tracked in https://bugs.swift.org/browse/SR-1127

Thanks for the report, though!