Add iOS client hang test

Summary: Check that it never hangs or crashes during startup

Reviewed By: priteshrnandgaonkar

Differential Revision: D10034630

fbshipit-source-id: b69ce9e6f91a5499a084c4d7328e6934ec92ece4

iOS/FlipperKit/FlipperClient.mm

@@ -61,14 +61,15 @@ using WrapperPlugin = facebook::flipper::FlipperCppWrapperPlugin;
     deviceName = [NSString stringWithFormat:@"%@ %@", [[UIDevice currentDevice] model], @"Simulator"];
 #endif
 
+    static const std::string UNKNOWN = std::string("unknown");
     facebook::flipper::FlipperClient::init({
       {
         "localhost",
         "iOS",
         [deviceName UTF8String],
-        "unknown",
-        [appName UTF8String],
-        [appId UTF8String],
+        UNKNOWN,
+        [appName UTF8String] ?: UNKNOWN,
+        [appId UTF8String] ?: UNKNOWN,
         [privateAppDirectory UTF8String],
       },
       sonarThread.getEventBase(),

iOS/SonarKitTests/FlipperClientTests.mm

@@ -0,0 +1,26 @@
+/*
+ *  Copyright (c) 2018-present, Facebook, Inc.
+ *
+ *  This source code is licensed under the MIT license found in the LICENSE
+ *  file in the root directory of this source tree.
+ *
+ */
+#import <XCTest/XCTest.h>
+
+#if FB_SONARKIT_ENABLED
+
+#import <FlipperKit/FlipperClient.h>
+
+@interface FlipperClientTests : XCTestCase
+@end
+
+@implementation FlipperClientTests
+
+- (void)testStartingClientDoesntCrashOrHang {
+  FlipperClient *client = [FlipperClient sharedClient];
+  [client start];
+}
+
+@end
+
+#endif