fix: added locker flag to tests

packages/@lwc/engine-core/src/framework/base-lightning-element.ts

@@ -244,9 +244,7 @@ export const LightningElement: LightningElementConstructor = function (
 
     setPrototypeOf(elm, bridge.prototype);
 
-    if (lwcRuntimeFlags.ENABLE_LEGACY_LOCKER_SUPPORT) {
-        vm.component = this;
-    }
+    vm.component = this;
 
     // Locker hooks assignment. When the LWC engine run with Locker, Locker intercepts all the new
     // component creation and passes hooks to instrument all the component interactions with the
@@ -259,9 +257,7 @@ export const LightningElement: LightningElementConstructor = function (
         vm.getHook = getHook;
     }
 
-    if (lwcRuntimeFlags.ENABLE_LEGACY_LOCKER_SUPPORT) {
-        markLockerLiveObject(this);
-    }
+    markLockerLiveObject(this);
 
     // Linking elm, shadow root and component with the VM.
     associateVM(this, vm);

packages/@lwc/engine-core/src/framework/invoker.ts

@@ -11,9 +11,10 @@ import { addErrorComponentStack } from '../shared/error';
 import { evaluateTemplate, setVMBeingRendered, getVMBeingRendered } from './template';
 import { runWithBoundaryProtection } from './vm';
 import { logOperationStart, logOperationEnd, OperationId } from './profiler';
+import { LightningElement } from './base-lightning-element';
 import type { Template } from './template';
 import type { VM } from './vm';
-import type { LightningElement, LightningElementConstructor } from './base-lightning-element';
+import type { LightningElementConstructor } from './base-lightning-element';
 import type { VNodes } from './vnodes';
 
 export let isInvokingRender: boolean = false;
@@ -59,7 +60,7 @@ export function invokeComponentConstructor(vm: VM, Ctor: LightningElementConstru
         // invoked by accessing the component on the vm.
         const isInvalidConstructor = lwcRuntimeFlags.ENABLE_LEGACY_LOCKER_SUPPORT
             ? vmBeingConstructed.component !== result
-            : !(result instanceof Ctor);
+            : !(result instanceof LightningElement);
 
         if (isInvalidConstructor) {
             throw new TypeError(

packages/@lwc/integration-karma/test/api/createElement/index.spec.js

@@ -1,4 +1,4 @@
-import { createElement, LightningElement } from 'lwc';
+import { createElement, LightningElement, setFeatureFlagForTest } from 'lwc';
 import { isNativeShadowRootInstance, isSyntheticShadowRootInstance } from 'test-utils';
 
 import Test from 'x/test';
@@ -97,6 +97,12 @@ describe.runIf(process.env.NATIVE_SHADOW)('native shadow', () => {
 });
 
 describe('locker integration', () => {
+    beforeEach(() => {
+        setFeatureFlagForTest('ENABLE_LEGACY_LOCKER_SUPPORT', true);
+    });
+    afterEach(() => {
+        setFeatureFlagForTest('ENABLE_LEGACY_LOCKER_SUPPORT', false);
+    });
     it('should support component class that extend a mirror of the LightningElement', () => {
         function SecureBaseClass() {
             if (this instanceof SecureBaseClass) {

packages/@lwc/integration-karma/test/component/LightningElement/index.spec.js

@@ -5,7 +5,7 @@ import NotReturningThis from 'x/notReturningThis';
 import ParentThrowingBeforeSuper from 'x/parentThrowingBeforeSuper';
 import DefinedComponent from 'x/definedComponent';
 import UndefinedComponent from 'x/undefinedComponent';
-import ReturningBad from 'x/returningBad'
+import ReturningBad from 'x/returningBad';
 
 it('should throw when trying to invoke the constructor manually', () => {
     const func = () => {
@@ -81,7 +81,7 @@ it("[W-6981076] shouldn't throw when a component with an invalid child in unmoun
     expect(() => document.body.removeChild(elm)).not.toThrow();
 });
 
-fit('should fail when the constructor returns something other than an instance of itself', () => {
+it('should fail when the constructor returns something other than an instance of itself', () => {
     expect(() => {
         createElement('x-returning-bad', { is: ReturningBad });
     }).toThrowError(

packages/@lwc/integration-karma/test/component/LightningElement/x/returningBad/returningBad.js

@@ -1,20 +1,12 @@
-import { LightningElement } from 'lwc'
+import { LightningElement } from 'lwc';
 
 export default class MyClass extends LightningElement {
     constructor() {
-        super()
+        super();
 
-        const bad = {}
-        LightningElement.call(bad)
+        const bad = {};
+        LightningElement.call(bad);
 
-        return bad
+        return bad;
     }
 }
-
-let counter = -1
-Object.defineProperty(MyClass, Symbol.hasInstance, {
-    value: function() {
-        console.log('counter', ++counter)
-        return true;
-    },
-});

packages/@lwc/integration-karma/test/integrations/locker/index.spec.js

@@ -1,9 +1,14 @@
-import { createElement } from 'lwc';
+import { createElement, setFeatureFlagForTest } from 'lwc';
 
 import LockerIntegration from 'x/lockerIntegration';
 import LockerLiveComponent from 'x/lockerLiveComponent';
 import LockerHooks, { hooks } from 'x/lockerHooks';
-
+beforeEach(() => {
+    setFeatureFlagForTest('ENABLE_LEGACY_LOCKER_SUPPORT', true);
+});
+afterEach(() => {
+    setFeatureFlagForTest('ENABLE_LEGACY_LOCKER_SUPPORT', false);
+});
 it('should support Locker integration which uses a wrapped LightningElement base class', () => {
     const elm = createElement('x-secure-parent', { is: LockerIntegration });
     document.body.appendChild(elm);