Getting this too (including another assertion failure in this log output, maybe it's relevant):
2017-10-05 14:46:18.837773+0200 FlashlightUITests-Runner[980:1157829] Running tests...
2017-10-05 14:46:19.828570+0200 FlashlightUITests-Runner[980:1157829] Continuing to run tests in the background with task ID 1
Test Suite 'All tests' started at 2017-10-05 14:46:19.912
Test Suite 'FlashlightUITests.xctest' started at 2017-10-05 14:46:19.913
Test Suite 'DashboardUITests' started at 2017-10-05 14:46:19.913
Test Case '-[FlashlightUITests.DashboardUITests testDashboardDisplaysValuesFromXXXXXXXX]' started.
t = 0.00s Start Test at 2017-10-05 14:46:19.914
t = 0.17s Set Up
t = 0.19s Open com.xxxxxxxx.Flashlight
t = 0.34s Launch com.xxxxxxxx.Flashlight
writeDictToFile:1278 ==== Successfully wrote Manifest cache to /var/folders/z9/6hbzfm7s5jv4k6cl6k06zmbm0000gn/C/com.apple.DeveloperTools/All/Xcode/EmbeddedAppDeltas/3355435a13029f4f09b0f386081f976e/2452e1bfb283cbebaf53dd2b36a8cd6a60ed516e/ManifestCache.plist
t = 5.67s Wait for com.xxxxxxxx.Flashlight to idle
t = 6.06s Unable to monitor animations
t = 6.06s Unable to monitor event loop
t = 7.10s Tap "gettingStartedButton" Button
t = 7.10s Wait for com.xxxxxxxx.Flashlight to idle
t = 7.28s Assertion Failure: <unknown>:0: com.xxxxxxxx.Flashlight crashed in <external symbol>
2017-10-05 14:46:27.414729+0200 FlashlightUITests-Runner[980:1157829] *** Assertion failure in -[XCActivityRecord _synchronized_ensureValid], /Library/Caches/com.apple.xbs/Sources/XCTest_iOS/XCTest-13201/Sources/XCTestFramework/Activities/XCActivityRecord.m:354
t = 7.50s Tear Down
t = 7.51s Assertion Failure: <unknown>:0: failed: caught "NSInternalInconsistencyException", "Activity cannot be used after its scope has completed."
(
0 CoreFoundation 0x0000000183662ff8 <redacted> + 148
1 libobjc.A.dylib 0x00000001820c4538 objc_exception_throw + 56
2 CoreFoundation 0x0000000183662eb4 <redacted> + 0
3 Foundation 0x00000001840fb760 <redacted> + 112
4 XCTest 0x000000010015049c -[XCActivityRecord _synchronized_ensureValid] + 160
5 XCTest 0x000000010014ff14 -[XCActivityRecord _synchronized_addAttachment:] + 44
6 XCTest 0x00000001001500c8 -[XCActivityRecord addAttachment:] + 44
7 XCTest 0x000000010013d050 -[XCActivityRecord(UITesting) attachAutomaticScreenshot] + 248
8 XCTest 0x0000000100157050 __67-[XCUIApplicationProcess waitForQuiescenceIncludingAnimationsIdle:]_block_invoke + 96
9 XCTest 0x000000010018e258 -[XCTContext _runActivityNamed:type:block:] + 204
10 XCTest 0x0000000100156fdc -[XCUIApplicationProcess waitForQuiescenceIncludingAnimationsIdle:] + 176
11 XCTest 0x00000001001a69ec __63-[XCUIElement(XCUIElementEventSynthesis) _dispatchEvent:block:]_block_invoke + 64
12 XCTest 0x000000010018e258 -[XCTContext _runActivityNamed:type:block:] + 204
13 XCTest 0x00000001001a692c -[XCUIElement(XCUIElementEventSynthesis) _dispatchEvent:block:] + 272
14 XCTest 0x00000001001a8544 -[XCUIElement(XCUIElementTouchEvents) tap] + 124
15 FlashlightUITests 0x0000000102271028 _T0So10XCTestCaseC17FlashlightUITestsE15connectXXXXXXXXySo15XCUIApplicationC3app_Sb6isFaketF + 404
16 FlashlightUITests 0x000000010227244c _T0So10XCTestCaseC17FlashlightUITestsE15connectXXXXXXXXySo15XCUIApplicationC3app_Sb6isFaketFTo + 92
17 FlashlightUITests 0x000000010226d8dc _T017FlashlightUITests09DashboardB0C04testC26DisplaysValuesFromXXXXXXXXyyF + 224
18 FlashlightUITests 0x000000010226e134 _T017FlashlightUITests09DashboardB0C04testC26DisplaysValuesFromXXXXXXXXyyFTo + 40
19 CoreFoundation 0x0000000183668e80 <redacted> + 144
20 CoreFoundation 0x000000018355e2c4 <redacted> + 292
21 XCTest 0x00000001001440a8 __24-[XCTestCase invokeTest]_block_invoke.275 + 48
22 XCTest 0x0000000100190f08 -[XCTMemoryChecker _assertInvalidObjectsDeallocatedAfterScope:] + 56
23 XCTest 0x0000000100143e58 __24-[XCTestCase invokeTest]_block_invoke + 680
24 XCTest 0x0000000100189780 -[XCUITestContext performInScope:] + 208
25 XCTest 0x0000000100143ba0 -[XCTestCase invokeTest] + 136
26 XCTest 0x0000000100144c78 __26-[XCTestCase performTest:]_block_invoke.382 + 48
27 XCTest 0x000000010018e778 +[XCTContext runInContextForTestCase:block:] + 164
28 XCTest 0x0000000100144674 -[XCTestCase performTest:] + 596
29 XCTest 0x0000000100140868 __27-[XCTestSuite performTest:]_block_invoke + 288
30 XCTest 0x0000000100140290 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 44
31 XCTest 0x00000001001404a0 -[XCTestSuite performTest:] + 236
32 XCTest 0x0000000100140868 __27-[XCTestSuite performTest:]_block_invoke + 288
33 XCTest 0x0000000100140290 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 44
34 XCTest 0x00000001001404a0 -[XCTestSuite performTest:] + 236
35 XCTest 0x0000000100140868 __27-[XCTestSuite performTest:]_block_invoke + 288
36 XCTest 0x0000000100140290 -[XCTestSuite _performProtectedSectionForTest:testSection:] + 44
37 XCTest 0x00000001001404a0 -[XCTestSuite performTest:] + 236
38 XCTest 0x0000000100197f5c __44-[XCTTestRunSession runTestsAndReturnError:]_block_invoke + 44
39 XCTest 0x00000001001533e8 -[XCTestObservationCenter _observeTestExecutionForBlock:] + 420
40 XCTest 0x0000000100197dd8 -[XCTTestRunSession runTestsAndReturnError:] + 292
41 XCTest 0x000000010012fed0 -[XCTestDriver runTestsAndReturnError:] + 312
42 XCTest 0x000000010018d920 _XCTestMain + 620
43 CoreFoundation 0x000000018361130c <redacted> + 20
44 CoreFoundation 0x0000000183610b28 <redacted> + 288
45 CoreFoundation 0x000000018360e998 <redacted> + 728
46 CoreFoundation 0x000000018353eda4 CFRunLoopRunSpecific + 424
47 GraphicsServices 0x0000000184fa9074 GSEventRunModal + 100
48 UIKit 0x00000001897f9c9c UIApplicationMain + 208
49 FlashlightUITests-Runner 0x0000000100080430 FlashlightUITests-Runner + 33840
50 libdyld.dylib 0x000000018254d59c <redacted> + 4