qrcode: wait for UI update in tests event when not calling fetch (#86853)

tests/js/qrcode.test.js

@@ -28,25 +28,22 @@ const certificateWithoutValidity =
 
 const qrcodeReaderTest = test.extend({
   mock: async ({ task }, use) => {
-    let resolveResult = undefined
-    let resultPromise = new Promise((resolve) => resolveResult = resolve)
-    let resolveResultHandled = undefined
+    let scanCallback = undefined
+    let scanPromise = new Promise((resolve) => scanCallback = resolve)
     const terminate = Symbol()
 
     class MockBrowserQRCodeReader {
       async decodeFromVideoDevice(device, element, callback) {
         while(true) {
-          const result = await resultPromise
+          const result = await scanPromise
 
           if(result === terminate) {
             return
           }
 
-          resultPromise = new Promise((resolve) => resolveResult = resolve)
+          scanPromise = new Promise((resolve) => scanCallback = resolve)
 
           callback({ text: result })
-
-          resolveResultHandled()
         }
       }
     }
@@ -69,9 +66,8 @@ const qrcodeReaderTest = test.extend({
     await use({
       reader,
       scan: async (text) => {
-        const resultHandled = new Promise((resolve) => resolveResultHandled = resolve)
-        resolveResult(text)
-        await resultHandled
+        scanCallback(text)
+        await new Promise((resolve) => setTimeout(resolve))
       }
     })
     vi.useRealTimers()
@@ -80,7 +76,8 @@ const qrcodeReaderTest = test.extend({
 
     reader.remove()
 
-    resolveResult(terminate)
+    scanCallback(terminate)
+
     window.ZXingBrowser = savedZXingBrowser
     navigator.mediaDevices = undefined
     window.nacl = undefined