fix: fix WORKERS_COUNT not found (#578)

Author: gregberge

packages/jest-environment-puppeteer/src/browsers.ts

@@ -80,14 +80,19 @@ export const startBrowsers = async ({
   config: JestPuppeteerConfig;
   jestConfig: JestConfig;
 }): Promise<Browser[]> => {
+  const workersCount = getWorkersCount(jestConfig);
+  saveWorkersCount(workersCount);
+
   if (config.connect?.browserWSEndpoint) {
+    if (workersCount > 1) {
+      throw new Error(
+        "Cannot use `connect.browserWSEndpoint` with multiple workers. Set Jest `maxWorkers` to 1.",
+      );
+    }
     saveWsEndpoints([config.connect.browserWSEndpoint]);
     return [];
   }
 
-  const workersCount = getWorkersCount(jestConfig);
-  saveWorkersCount(workersCount);
-
   const browsers = await Promise.all(
     Array.from({ length: workersCount }).map(() => openBrowser(config)),
   );