fix(component-testing): wait for iframe to exist to start testing (#1…

…5354)

* fix: wait for iframe to exist to start testing

* add comment

Co-authored-by: Lachlan Miller <lachlan.miller.1990@outlook.com>

packages/driver/src/cypress.js

@@ -159,6 +159,10 @@ class $Cypress {
   initialize ({ $autIframe, onSpecReady }) {
     this.$autIframe = $autIframe
     this.onSpecReady = onSpecReady
+    if (this._onInitialize) {
+      this._onInitialize()
+      this._onInitialize = undefined
+    }
   }
 
   run (fn) {
@@ -216,6 +220,17 @@ class $Cypress {
 
       this.runner.onScriptError(err)
     })
+    .then(() => {
+      return (new Promise((resolve) => {
+        if (this.$autIframe) {
+          resolve()
+        } else {
+          // block initialization if the iframe has not been created yet
+          // Used in CT when async chunks for plugins take their time to download/parse
+          this._onInitialize = resolve
+        }
+      }))
+    })
     .then(() => {
       this.cy.initialize(this.$autIframe)