Improve unit tests code coverage on ios

lib/ios/ReactNativeNavigationTests/RNNNavigationStackManagerTest.m

 
 @interface RNNNavigationStackManagerTest : XCTestCase
 
-@property (nonatomic, strong) RNNStore *store;
 @property (nonatomic, strong) UINavigationController *nvc;
 @property (nonatomic, strong) UIViewController *vc1;
 @property (nonatomic, strong) UIViewController *vc2;
 
 - (void)setUp {
     [super setUp];
-	self.store = [RNNStore new];
 	
 	self.nvc = [[UINavigationController alloc] init];
 	self.vc1 = [RNNRootViewController new];

lib/ios/ReactNativeNavigationTests/RNNOverlayManagerTest.m

 	XCTAssertFalse([_overlayManager.overlayWindows containsObject:window]);
 }
 
+- (void)testDismissOverlayShouldNotRemoveWrongVC {
+	[_overlayManager showOverlay:_overlayVC];
+	UIWindow* window = _overlayManager.overlayWindows.lastObject;
+	[_overlayManager dismissOverlay:[UIViewController new]];
+	XCTAssertTrue([_overlayManager.overlayWindows containsObject:window]);
+}
+
 @end

lib/ios/ReactNativeNavigationTests/RNNStoreTest.m

 	XCTAssertNil([self.store findComponentForId:@"cntId1"]);
 }
 
+- (void)testGetExternalComponentShouldRetrunSavedComponent {
+	UIViewController* testVC = [UIViewController new];
+	NSString *externalComponentId = @"extId1";
+	[self.store registerExternalComponent:externalComponentId callback:^UIViewController *(NSDictionary *props, RCTBridge *bridge) {
+		return testVC;
+	}];
+	
+	UIViewController* savedComponent = [self.store getExternalComponent:externalComponentId props:nil bridge:nil];
+	XCTAssertEqual(testVC, savedComponent);
+}
+
+- (void)testComponentKeyForInstance_UknownComponentShouldReturnNil {
+	id result = [self.store componentKeyForInstance:[UIViewController new]];
+	XCTAssertNil(result);
+}
+
+-(void)testCleanStore {
+	[self.store clean];
+	XCTAssertFalse(self.store.pendingModalIdsToDismiss.count);
+	XCTAssertFalse(self.store.isReadyToReceiveCommands);
+}
 
 #pragma mark - private