test: Improve SentryReachabilityTests

The SentryReachabilityTests are still sometimes failing in CI. We now
skip registering and unregistering the actual callbacks to
SCNetworkReachability for all tests except one to minimize side effects.

Sources/Sentry/SentryReachability.m

@@ -44,6 +44,7 @@
 void
 SentrySetReachabilityIgnoreActualCallback(BOOL value)
 {
+    SENTRY_LOG_DEBUG(@"Setting ignore actual callback to %@", value ? @"YES" : @"NO");
     sentry_reachability_ignore_actual_callback = value;
 }
 
@@ -155,6 +156,15 @@ + (void)initialize
     }
 }
 
+- (instancetype)init
+{
+    if (self = [super init]) {
+        self.skipRegisteringActualCallbacks = NO;
+    }
+
+    return self;
+}
+
 - (void)addObserver:(id<SentryReachabilityObserver>)observer;
 {
     SENTRY_LOG_DEBUG(@"Adding observer: %@", observer);
@@ -171,6 +181,11 @@ - (void)addObserver:(id<SentryReachabilityObserver>)observer;
             return;
         }
 
+        if (self.skipRegisteringActualCallbacks) {
+            SENTRY_LOG_DEBUG(@"Skip registering actual callbacks");
+            return;
+        }
+
         sentry_reachability_queue
             = dispatch_queue_create("io.sentry.cocoa.connectivity", DISPATCH_QUEUE_SERIAL);
         // Ensure to call CFRelease for the return value of SCNetworkReachabilityCreateWithName, see
@@ -214,6 +229,10 @@ - (void)removeAllObservers
 
 - (void)unsetReachabilityCallback
 {
+    if (self.skipRegisteringActualCallbacks) {
+        SENTRY_LOG_DEBUG(@"Skip unsetting actual callbacks");
+    }
+
     sentry_current_reachability_state = kSCNetworkReachabilityFlagsUninitialized;
 
     if (_sentry_reachability_ref != nil) {

Sources/Sentry/include/SentryReachability.h

@@ -65,6 +65,12 @@ SENTRY_EXTERN NSString *const SentryConnectivityNone;
  */
 @interface SentryReachability : NSObject
 
+/**
+ * Only needed for testing. Use this flag to skip registering and unregistering the actual callbacks
+ * to SCNetworkReachability to minimize side effects.
+ */
+@property (nonatomic, assign) BOOL skipRegisteringActualCallbacks;
+
 /**
  * Add an observer which is called each time network connectivity changes.
  */

Tests/SentryTests/Networking/SentryReachabilityTests.m

@@ -35,11 +35,13 @@ @implementation SentryReachabilityTest
 
 - (void)setUp
 {
-    self.reachability = [[SentryReachability alloc] init];
     // Ignore the actual reachability callbacks, cause we call the callbacks manually.
     // Otherwise, the actual reachability callbacks are called during later unrelated tests causing
     // flakes.
     SentrySetReachabilityIgnoreActualCallback(YES);
+
+    self.reachability = [[SentryReachability alloc] init];
+    self.reachability.skipRegisteringActualCallbacks = YES;
 }
 
 - (void)tearDown
@@ -145,5 +147,19 @@ - (void)testReportSameReachabilityState_OnlyCalledOnce
     [self.reachability removeObserver:observer];
 }
 
+/**
+ * We only want to make sure running the actual registering and unregistering callbacks doesn't
+ * crash.
+ */
+- (void)testRegisteringActualCallbacks
+{
+    self.reachability.skipRegisteringActualCallbacks = NO;
+
+    TestSentryReachabilityObserver *observer = [[TestSentryReachabilityObserver alloc] init];
+
+    [self.reachability addObserver:observer];
+    [self.reachability removeObserver:observer];
+}
+
 @end
 #endif // !TARGET_OS_WATCH