fix(testing): reduce flakiness in extension e2e tests (#5481)

test/e2e/models/CodeServer.ts

@@ -296,6 +296,16 @@ export class CodeServerPage {
     return visible
   }
 
+  /**
+   * Checks if the test extension loaded
+   */
+  async waitForTestExtensionLoaded(): Promise<void> {
+    const selector = "text=test extension loaded"
+    this.codeServer.logger.debug("Waiting for test extension to load...")
+
+    await this.page.waitForSelector(selector)
+  }
+
   /**
    * Focuses the integrated terminal by navigating through the command palette.
    *