xcodebuild -version
Xcode 7.3
Build version 7D141l

xctool -v
0.2.8

  [Info] Collecting info for testables...2016-02-15 03:33:36.894 xctool[90639:6934729]  DVTAssertions: ASSERTION FAILURE in /Library/Caches/com.apple.xbs/Sources/DVTFrameworks/DVTFrameworks-10150.2/DVTFoundation/FoundationClassCategories/DVTNSBundleAdditions.m:24
Details:  Assertion failed: [NSThread isMainThread]
Function: NSBundle *_DVTFoundationBundle()
Thread:   <NSThread: 0x7fa7bad3e6e0>{number = 2, name = (null)}
Hints: None
Backtrace:
  0   -[DVTAssertionHandler handleFailureInFunction:fileName:lineNumber:assertionSignature:messageFormat:arguments:] (in DVTFoundation)
  1   _DVTAssertionHandler (in DVTFoundation)
  2   _DVTAssertionFailureHandler (in DVTFoundation)
  3   _DVTAssertionFailureHandler (in DVTFoundation)
  4   _DVTFoundationBundle (in DVTFoundation)
  5   -[DVTDeveloperPaths _developerFolderPath] (in DVTFoundation)
  6   -[DVTDeveloperPaths init] (in DVTFoundation)
  7   __33+[DVTDeveloperPaths defaultPaths]_block_invoke (in DVTFoundation)
  8   _dispatch_client_callout (in libdispatch.dylib)
  9   dispatch_once_f (in libdispatch.dylib)
 10   +[DVTDeveloperPaths defaultPaths] (in DVTFoundation)
 11   __60+[SimServiceContext(DVTAdditions) dvt_sharedServiceContext:]_block_invoke (in DVTiPhoneSimulatorRemoteClient)
 12   _dispatch_client_callout (in libdispatch.dylib)
 13   dispatch_once_f (in libdispatch.dylib)
 14   +[SimServiceContext(DVTAdditions) dvt_sharedServiceContext:] (in DVTiPhoneSimulatorRemoteClient)
 15   __41+[DTiPhoneSimulatorSystemRoot initialize]_block_invoke (in DVTiPhoneSimulatorRemoteClient)
 16   _dispatch_client_callout (in libdispatch.dylib)
 17   dispatch_once_f (in libdispatch.dylib)
 18   +[DTiPhoneSimulatorSystemRoot initialize] (in DVTiPhoneSimulatorRemoteClient)
 19   _class_initialize (in libobjc.A.dylib)
 20   lookUpImpOrForward (in libobjc.A.dylib)
 21   objc_msgSend (in libobjc.A.dylib)
 22   +[SimulatorInfo _systemRootWithSDKVersion:] (in xctool)
 23   -[SimulatorInfo systemRootForSimulatedSdk] (in xctool)
 24   -[SimulatorInfo simulatedRuntime] (in xctool)
 25   -[SimulatorInfo simulatedDevice] (in xctool)
 26   CreateTaskForSimulatorExecutable (in xctool)
 27   -[OCUnitIOSLogicTestQueryRunner createTaskForQuery] (in xctool)
 28   -[OCUnitTestQueryRunner runQueryWithError:] (in xctool)
 29   +[TestableExecutionInfo queryTestCasesWithSimulatorInfo:error:] (in xctool)
 30   +[TestableExecutionInfo infoForTestable:buildSettings:simulatorInfo:] (in xctool)
 31   __56-[RunTestsAction runTestables:options:xcodeSubjectInfo:]_block_invoke (in xctool)
 32   _dispatch_call_block_and_release (in libdispatch.dylib)
 33   _dispatch_client_callout (in libdispatch.dylib)
 34   _dispatch_queue_drain (in libdispatch.dylib)
 35   _dispatch_queue_invoke (in libdispatch.dylib)
 36   _dispatch_client_callout (in libdispatch.dylib)
 37   _dispatch_root_queue_drain (in libdispatch.dylib)
 38   _dispatch_worker_thread3 (in libdispatch.dylib)
 39   _pthread_wqthread (in libsystem_pthread.dylib)
 40   start_wqthread (in libsystem_pthread.dylib)
Abort trap: 6