diff --git a/src/frames.ts b/src/frames.ts
index dbbace39d4..ddd9789579 100644
--- a/src/frames.ts
+++ b/src/frames.ts
@@ -21,7 +21,7 @@ import { ConsoleMessage } from './console';
 import * as dom from './dom';
 import { TimeoutError, NotConnectedError } from './errors';
 import { Events } from './events';
-import { assert, helper, RegisteredListener, assertMaxArguments } from './helper';
+import { assert, helper, RegisteredListener, assertMaxArguments, debugAssert } from './helper';
 import * as js from './javascript';
 import * as network from './network';
 import { Page } from './page';
@@ -149,7 +149,7 @@ export class FrameManager {
     this.removeChildFramesRecursively(frame);
     frame._url = url;
     frame._name = name;
-    assert(!frame._pendingDocumentId || frame._pendingDocumentId === documentId);
+    debugAssert(!frame._pendingDocumentId || frame._pendingDocumentId === documentId);
     frame._lastDocumentId = documentId;
     frame._pendingDocumentId = '';
     for (const task of frame._frameTasks)
diff --git a/src/helper.ts b/src/helper.ts
index 43b7825da6..b1dbca4fab 100644
--- a/src/helper.ts
+++ b/src/helper.ts
@@ -337,6 +337,21 @@ export function assert(value: any, message?: string): asserts value {
     throw new Error(message);
 }
 
+let _isUnderTest = false;
+
+export function setUnderTest() {
+  _isUnderTest = true;
+}
+
+export function isUnderTest(): boolean {
+  return _isUnderTest;
+}
+
+export function debugAssert(value: any, message?: string): asserts value {
+  if (_isUnderTest && !value)
+    throw new Error(message);
+}
+
 export function assertMaxArguments(count: number, max: number): asserts count {
   assert(count <= max, 'Too many arguments. If you need to pass more than 1 argument to the function wrap them in an object.');
 }
diff --git a/test/test.js b/test/test.js
index 526393d9aa..844f30c55c 100644
--- a/test/test.js
+++ b/test/test.js
@@ -16,7 +16,6 @@
  */
 
 const fs = require('fs');
-const readline = require('readline');
 const TestRunner = require('../utils/testrunner/');
 const {Environment} = require('../utils/testrunner/Test');
 
@@ -74,6 +73,8 @@ function collect(browserNames) {
   // TODO: this should be a preinstalled playwright by default.
   const playwrightPath = config.playwrightPath;
   const playwright = require(playwrightPath);
+  const { setUnderTest } = require(require('path').join(playwrightPath, 'lib/helper.js'));
+  setUnderTest();
 
   const playwrightEnvironment = new Environment('Playwright');
   playwrightEnvironment.beforeAll(async state => {