Force browser window focus with a minimize/restore (#26)

* Force browser window focus with a minimize/restore

* add comment

src/agent/driver-test-runner.js

@@ -48,6 +48,13 @@ export class DriverTestRunner {
   async openPage({ url, referencePage }) {
     await this.log(AgentMessage.OPEN_PAGE, { url });
     await this.webDriver.switchTo().defaultContent();
+    // Minimizing then restoring the window is recommended to trick the window
+    // manager on the OS to put focus in the browser. This is needed to
+    // steal focus away from a terminal/powershell tab if you launch the tests
+    // locally.
+    await this.webDriver.manage().window().minimize();
+    await this.webDriver.manage().window().setRect({ x: 0, y: 0 });
+    await this.webDriver.switchTo().defaultContent();
     await this.webDriver.navigate().to(url.toString());
 
     try {