diff --git a/Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m b/Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m
index a3bcde2548a41b..81ccffa35b4096 100644
--- a/Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m
+++ b/Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m
@@ -69,13 +69,40 @@ - (void)invalidate
 @interface RCTAllocationTests : XCTestCase
 @end
 
-@implementation RCTAllocationTests
+@implementation RCTAllocationTests {
+  NSURL *_bundleURL;
+}
+
+- (void)setUp
+{
+  [super setUp];
+
+  NSString *bundleContents =
+  @"var __fbBatchedBridge = {"
+   "  callFunctionReturnFlushedQueue: function() {},"
+   "  invokeCallbackAndReturnFlushedQueue: function() {},"
+   "  flushedQueue: function() {},"
+   "};";
+
+  NSURL *tempDir = [NSURL fileURLWithPath:NSTemporaryDirectory() isDirectory:YES];
+  [[NSFileManager defaultManager] createDirectoryAtURL:tempDir withIntermediateDirectories:YES attributes:nil error:NULL];
+
+  _bundleURL = [tempDir URLByAppendingPathComponent:@"rctallocationtests-bundle.js"];
+  [bundleContents writeToURL:_bundleURL atomically:YES encoding:NSUTF8StringEncoding error:NULL];
+}
+
+- (void)tearDown
+{
+  [super tearDown];
+
+  [[NSFileManager defaultManager] removeItemAtURL:_bundleURL error:NULL];
+}
 
 - (void)testBridgeIsDeallocated
 {
   __weak RCTBridge *weakBridge;
   @autoreleasepool {
-    RCTRootView *view = [[RCTRootView alloc] initWithBundleURL:nil
+    RCTRootView *view = [[RCTRootView alloc] initWithBundleURL:_bundleURL
                                                     moduleName:@""
                                              initialProperties:nil
                                                  launchOptions:nil];
@@ -91,7 +118,7 @@ - (void)testModulesAreInvalidated
 {
   AllocationTestModule *module = [AllocationTestModule new];
   @autoreleasepool {
-    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:nil
+    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL
                                               moduleProvider:^{
                                                 return @[module];
                                               }
@@ -109,11 +136,11 @@ - (void)testModulesAreDeallocated
   __weak AllocationTestModule *weakModule;
   @autoreleasepool {
     AllocationTestModule *module = [AllocationTestModule new];
-    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:nil
-                                moduleProvider:^{
-                                  return @[module];
-                                }
-                                 launchOptions:nil];
+    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL
+                                              moduleProvider:^{
+                                                return @[module];
+                                              }
+                                               launchOptions:nil];
     weakModule = module;
     XCTAssertNotNil(weakModule, @"AllocationTestModule should have been created");
     (void)bridge;
@@ -140,7 +167,7 @@ - (void)testJavaScriptExecutorIsDeallocated
 {
   __weak id<RCTJavaScriptExecutor> weakExecutor;
   @autoreleasepool {
-    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:nil
+    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL
                                               moduleProvider:nil
                                                launchOptions:nil];
     weakExecutor = [bridge.batchedBridge valueForKey:@"javaScriptExecutor"];
@@ -156,7 +183,7 @@ - (void)testJavaScriptContextIsDeallocated
 {
   __weak id weakContext;
   @autoreleasepool {
-    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:nil
+    RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL
                                               moduleProvider:nil
                                                launchOptions:nil];
     id executor = [bridge.batchedBridge valueForKey:@"javaScriptExecutor"];
@@ -171,7 +198,7 @@ - (void)testJavaScriptContextIsDeallocated
 
 - (void)testContentViewIsInvalidated
 {
-  RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:nil
+  RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL
                                             moduleProvider:nil
                                              launchOptions:nil];
   __weak UIView *rootContentView;
@@ -190,7 +217,7 @@ - (void)testUnderlyingBridgeIsDeallocated
   RCTBridge *bridge;
   __weak id batchedBridge;
   @autoreleasepool {
-    bridge = [[RCTBridge alloc] initWithBundleURL:nil moduleProvider:nil launchOptions:nil];
+    bridge = [[RCTBridge alloc] initWithBundleURL:_bundleURL moduleProvider:nil launchOptions:nil];
     batchedBridge = bridge.batchedBridge;
     XCTAssertTrue([batchedBridge isValid], @"RCTBatchedBridge should be valid");
     [bridge reload];
diff --git a/React/Executors/RCTJSCExecutor.m b/React/Executors/RCTJSCExecutor.m
index 1d52ae5c9522ea..b2d432be3883eb 100644
--- a/React/Executors/RCTJSCExecutor.m
+++ b/React/Executors/RCTJSCExecutor.m
@@ -119,8 +119,8 @@ @implementation RCTJSCExecutor
 
 static NSError *RCTNSErrorFromJSError(JSContextRef context, JSValueRef jsError)
 {
-  NSString *errorMessage = jsError ? RCTJSValueToNSString(context, jsError, NULL) : @"unknown JS error";
-  NSString *details = jsError ? RCTJSValueToJSONString(context, jsError, NULL, 2) : @"no details";
+  NSString *errorMessage = jsError ? RCTJSValueToNSString(context, jsError, NULL) : @"Unknown JS error";
+  NSString *details = jsError ? RCTJSValueToJSONString(context, jsError, NULL, 2) : @"No details";
   return [NSError errorWithDomain:@"JS" code:1 userInfo:@{NSLocalizedDescriptionKey: errorMessage, NSLocalizedFailureReasonErrorKey: details}];
 }
 
@@ -394,14 +394,12 @@ - (void)_executeJSCall:(NSString *)method
     JSStringRelease(moduleNameJSStringRef);
 
     if (moduleJSRef != NULL && errorJSRef == NULL && !JSValueIsUndefined(contextJSRef, moduleJSRef)) {
-
       // get method
       JSStringRef methodNameJSStringRef = JSStringCreateWithCFString((__bridge CFStringRef)method);
       JSValueRef methodJSRef = JSObjectGetProperty(contextJSRef, (JSObjectRef)moduleJSRef, methodNameJSStringRef, &errorJSRef);
       JSStringRelease(methodNameJSStringRef);
 
-      if (methodJSRef != NULL && errorJSRef == NULL) {
-
+      if (methodJSRef != NULL && errorJSRef == NULL && !JSValueIsUndefined(contextJSRef, methodJSRef)) {
         // direct method invoke with no arguments
         if (arguments.count == 0) {
           resultJSRef = JSObjectCallAsFunction(contextJSRef, (JSObjectRef)methodJSRef, (JSObjectRef)moduleJSRef, 0, NULL, &errorJSRef);
@@ -433,11 +431,22 @@ - (void)_executeJSCall:(NSString *)method
             JSStringRelease(argsJSStringRef);
           }
         }
+      } else {
+        if (!errorJSRef && JSValueIsUndefined(contextJSRef, methodJSRef)) {
+          error = RCTErrorWithMessage([NSString stringWithFormat:@"Unable to execute JS call: method %@ is undefined", method]);
+        }
+      }
+    } else {
+      if (!errorJSRef && JSValueIsUndefined(contextJSRef, moduleJSRef)) {
+        error = RCTErrorWithMessage(@"Unable to execute JS call: __fbBatchedBridge is undefined");
       }
     }
 
-    if (errorJSRef) {
-      onComplete(nil, RCTNSErrorFromJSError(contextJSRef, errorJSRef));
+    if (errorJSRef || error) {
+      if (!error) {
+        error = RCTNSErrorFromJSError(contextJSRef, errorJSRef);
+      }
+      onComplete(nil, error);
       return;
     }