test RCTInstance initialization (#37860)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/37860

Changelog: [Internal]

Reviewed By: cipolleschi

Differential Revision: D46547013

fbshipit-source-id: 2b1593799ce2b5d29e7ea6df4373ff6c92b51065

packages/react-native/ReactCommon/react/bridgeless/iostests/RCTHostTests.mm

@@ -40,10 +40,18 @@ static ShimRCTInstance *shimmedRCTInstance;
                                }];
 }
 
+- (void)tearDown
+{
+  [shimmedRCTInstance reset];
+
+  [super tearDown];
+}
+
 - (void)testStart
 {
   [_subject start];
   OCMVerify(OCMTimes(1), [_mockHostDelegate hostDidStart:_subject]);
+  XCTAssertEqual(shimmedRCTInstance.initCount, 1);
 }
 
 @end

packages/react-native/ReactCommon/react/test_utils/ios/Shims/ShimRCTInstance.h

@@ -8,4 +8,9 @@
 #import <Foundation/Foundation.h>
 
 @interface ShimRCTInstance : NSObject
+
+@property (assign) int initCount;
+
+- (void)reset;
+
 @end

packages/react-native/ReactCommon/react/test_utils/ios/Shims/ShimRCTInstance.mm

@@ -11,20 +11,34 @@
 
 #import "RCTSwizzleHelpers.h"
 
+static __weak ShimRCTInstance *weakShim = nil;
+
 @implementation ShimRCTInstance
 
 - (instancetype)init
 {
   if (self = [super init]) {
+    _initCount = 0;
     RCTSwizzleInstanceSelector(
         [RCTInstance class],
         [ShimRCTInstance class],
         @selector(initWithDelegate:
                   jsEngineInstance:bundleManager:turboModuleManagerDelegate:onInitialBundleLoad:moduleRegistry:));
+    weakShim = self;
   }
   return self;
 }
 
+- (void)reset
+{
+  RCTSwizzleInstanceSelector(
+      [RCTInstance class],
+      [ShimRCTInstance class],
+      @selector(initWithDelegate:
+                jsEngineInstance:bundleManager:turboModuleManagerDelegate:onInitialBundleLoad:moduleRegistry:));
+  _initCount = 0;
+}
+
 - (instancetype)initWithDelegate:(id<RCTInstanceDelegate>)delegate
                 jsEngineInstance:(std::shared_ptr<facebook::react::JSEngineInstance>)jsEngineInstance
                    bundleManager:(RCTBundleManager *)bundleManager
@@ -32,6 +46,7 @@
              onInitialBundleLoad:(RCTInstanceInitialBundleLoadCompletionBlock)onInitialBundleLoad
                   moduleRegistry:(RCTModuleRegistry *)moduleRegistry
 {
+  weakShim.initCount++;
   return self;
 }