fix(testing): remove use of emulate field in E2EPage() (#4632)

* expose `emulate` on page

* remove previous emulate logic tied to screenshot tests

* re-remove `emulate` method on exposed page

* update documentation on existing `emulate` testing config field

src/declarations/stencil-public-compiler.ts

@@ -1806,8 +1806,11 @@ export interface TestingConfig extends JestConfig {
   browserDevtools?: boolean;
 
   /**
-   * Array of browser emulations to be using during e2e tests. A full e2e
+   * Array of browser emulations to be used during _screenshot_ tests. A full screenshot
    * test is ran for each emulation.
+   *
+   * To emulate a device display for your e2e tests, use the `setViewport` method on a test's E2E page.
+   * An example can be found in [the Stencil docs](https://stenciljs.com/docs/end-to-end-testing#emulate-a-display).
    */
   emulate?: EmulateConfig[];
 

src/testing/puppeteer/puppeteer-page.ts

@@ -1,5 +1,5 @@
-import type { E2EProcessEnv, EmulateConfig, HostElement, JestEnvironmentGlobal } from '@stencil/core/internal';
-import type { ConsoleMessage, ConsoleMessageLocation, ElementHandle, JSHandle, Page, WaitForOptions } from 'puppeteer';
+import type { E2EProcessEnv, HostElement, JestEnvironmentGlobal } from '@stencil/core/internal';
+import type { ConsoleMessage, ConsoleMessageLocation, ElementHandle, JSHandle, WaitForOptions } from 'puppeteer';
 
 import type {
   E2EPage,
@@ -30,7 +30,6 @@ export async function newE2EPage(opts: NewE2EPageOptions = {}): Promise<E2EPage>
     page._e2eGoto = page.goto;
     page._e2eClose = page.close;
 
-    await setPageEmulate(page as any);
     await page.setCacheEnabled(false);
     await initPageEvents(page);
 
@@ -276,26 +275,6 @@ async function waitForStencil(page: E2EPage, options: WaitForOptions) {
   }
 }
 
-async function setPageEmulate(page: Page) {
-  if (page.isClosed()) {
-    return;
-  }
-
-  const emulateJsonContent = env.__STENCIL_EMULATE__;
-  if (!emulateJsonContent) {
-    return;
-  }
-
-  const screenshotEmulate = JSON.parse(emulateJsonContent) as EmulateConfig;
-
-  const emulateOptions = {
-    viewport: screenshotEmulate.viewport,
-    userAgent: screenshotEmulate.userAgent,
-  };
-
-  await (page as Page).emulate(emulateOptions);
-}
-
 async function waitForChanges(page: E2EPageInternal) {
   try {
     if (page.isClosed()) {