Fetch correct Firefox profile name based on WEB_EXT_FIREFOX env var

packages/react-devtools-extensions/firefox/README.md

@@ -2,7 +2,7 @@
 
 The source code for this extension has moved to `shells/webextension`.
 
-Modify the source code there and then rebuild this extension by running `node build` from this directory or `yarn run build:extension:firefox` from the root directory.
+Modify the source code there and then rebuild this extension by running `node build` from this directory or `yarn run build:firefox` from the root directory.
 
 ## Testing in Firefox
 

packages/react-devtools-extensions/firefox/test.js

@@ -10,13 +10,32 @@ const {argv} = require('yargs');
 const EXTENSION_PATH = resolve('./firefox/build/unpacked');
 const START_URL = argv.url || 'https://reactjs.org/';
 
+const ffVersion = process.env.WEB_EXT_FIREFOX;
+
+const getFFProfileName = () => {
+  // Keys are pulled from https://extensionworkshop.com/documentation/develop/web-ext-command-reference/#--firefox
+  // and profile names from https://searchfox.org/mozilla-central/source/toolkit/profile/xpcshell/head.js#96
+  switch (ffVersion) {
+    case 'firefox':
+      return 'default-release';
+    case 'beta':
+      return 'default-beta';
+    case 'nightly':
+      return 'default-nightly';
+    case 'firefoxdeveloperedition':
+      return 'dev-edition-default';
+    default:
+      return 'default';
+  }
+};
+
 const main = async () => {
   const finder = new Finder();
 
   // Use default Firefox profile for testing purposes.
   // This prevents users from having to re-login-to sites before testing.
   const findPathPromise = new Promise((resolvePromise, rejectPromise) => {
-    finder.getPath('default', (error, profile) => {
+    finder.getPath(getFFProfileName(), (error, profile) => {
       if (error) {
         rejectPromise(error);
       } else {