Improve C4 object leak check in tests (#3483)

Cherry-picked this from release/4.0 branch.

* Created a utility function for interval waiting and checking using runloop spinning to avoid main thread block error warning. This is required when running with the host app on the actual iOS devices otherwise the tests could fail as blocking the main thread on the recent XCode.

* Increased the timeout period from 2 seconds to 8 seconds.

* Made a constant variable for disabling MultipeerReplicatorTest.

Author: pasin

Objective-C/Tests/CBLTestCase.h

@@ -215,6 +215,11 @@ extern const NSTimeInterval kExpTimeout;
  */
 - (XCTestExpectation*) allowOverfillExpectationWithDescription:(NSString *)description;
 
+/** A utility function for waiting for the condition or timeout, spinning the run loop without blocking. */
+- (BOOL) waitWithTimeout: (NSTimeInterval)timeout
+                interval: (NSTimeInterval)interval
+                   until: (BOOL (^)(void))condition;
+
 @end
 
 NS_ASSUME_NONNULL_END

Objective-C/Tests/CBLTestCase.m

@@ -79,15 +79,12 @@ - (void) tearDown {
 
     if (!_disableObjectLeakCheck) {
         // Wait a little while for objects to be cleaned up:
-        int leaks = 0;
-        for (int i = 0; i < 20; i++) {
-            leaks = c4_getObjectCount() - _c4ObjectCount;
-            if (leaks == 0)
-                break;
-            else
-                [NSThread sleepForTimeInterval: 0.1];
-        }
-        if (leaks) {
+        __block int leaks = 0;
+        BOOL success = [self waitWithTimeout: 8 interval: 0.5 until: ^BOOL{
+            leaks = c4_getObjectCount() - self->_c4ObjectCount;
+            return leaks == 0;
+        }];
+        if (!success) {
             fprintf(stderr, "**** LITECORE OBJECTS STILL NOT FREED: ****\n");
             c4_dumpInstances();
             XCTFail("%d LiteCore objects have not been freed (see above)", leaks);
@@ -479,4 +476,18 @@ - (NSString*) getRickAndMortyJSON {
     return [self stringFromResource: @"rick_morty" ofType: @"json"];
 }
 
+- (BOOL) waitWithTimeout: (NSTimeInterval)timeout
+                interval: (NSTimeInterval)interval
+                   until: (BOOL (^)(void))condition {
+    NSDate *deadline = [NSDate dateWithTimeIntervalSinceNow: timeout];
+    while ([deadline timeIntervalSinceNow] > 0) {
+        if (condition()) {
+            return YES;
+        }
+        [[NSRunLoop currentRunLoop] runMode: NSDefaultRunLoopMode
+                                 beforeDate: [NSDate dateWithTimeIntervalSinceNow: interval]];
+    }
+    return condition();
+}
+
 @end

Objective-C/Tests/MultipeerReplicatorTest.m

@@ -16,6 +16,9 @@
 #define kTestMaxIdentity 10
 #define kTestIdentityCommonName @"CBLMultipeerReplTest"
 
+// Disable as cannot be run on the build VM (Got POSIX Error 50, Network is down)
+#define kDisableMultipeerTests YES
+
 typedef NSMutableDictionary<CBLPeerID*, CBLPeerReplicatorStatus*> CBLPeerReplicatorStatusMap;
 
 typedef CBLDocument * _Nullable (^MultipeerConflictResolverBlock)(CBLPeerID*, CBLConflict*);
@@ -67,6 +70,9 @@ - (void) setUp {
 
     XCTSkipUnless(self.isExecutionAllowed);
 
+    // Disabled by testConfigurationValidation, ensure to re-enable the leak check:
+    self.disableObjectLeakCheck = NO;
+    
     [self cleanupIdentities];
     [self openOtherDB];
 
@@ -85,13 +91,12 @@ - (void) tearDown {
 
 // TODO: Too flaky, enable after all LiteCore issues have been handled.
 - (BOOL) isExecutionAllowed {
-#if TARGET_OS_SIMULATOR || TARGET_OS_MACCATALYST || TARGET_OS_OSX
+#if TARGET_OS_SIMULATOR
     // Cannot be tested on the simulator as local network access permission is required.
     // See FAQ-12 : https://developer.apple.com/forums/thread/663858)
     return NO;
 #else
-    // Disable as cannot be run on the build VM (Got POSIX Error 50, Network is down)
-    return self.keyChainAccessAllowed;
+    return kDisableMultipeerTests ? NO : self.keyChainAccessAllowed;
 #endif
 }
 

Swift/Tests/MultipeerReplicatorTest.swift

@@ -34,6 +34,9 @@ class MultipeerReplicatorTest: CBLTestCase {
         }
     }
 
+    // Disable as cannot be run on the build VM (Got POSIX Error 50, Network is down)
+    let kDisableMultipeerReplicatorTest = true
+    
     let kTestKeyUsages: KeyUsages = [.clientAuth, .serverAuth]
 
     let kTestPeerGroupID = "CBLMultipeerReplTestGroup"
@@ -59,8 +62,7 @@ class MultipeerReplicatorTest: CBLTestCase {
         // See FAQ-12: https://developer.apple.com/forums/thread/663858
         return false
 #else
-        // Disable as cannot be run on the build VM (Got POSIX Error 50, Network is down)
-        return keyChainAccessAllowed && false
+        return kDisableMultipeerReplicatorTest ? false : keyChainAccessAllowed;
 #endif
     }