Index: README.md
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 ### Running the browser tests in a real browser
 
 The tests under `test/browser` require a browser environment. `npm test` will
 run these in a headless browser, with each module being loaded in a new frame.
 
 The default is to run in both Chromium (using the remote interface)
 and Firefox. You can select which runners to use by setting the
 BROWSER_TEST_RUNNERS environment, the default is
-"chromium_remote,firefox". Possible values (separated by a ',') are:
+"chromium_remote". Possible values (separated by a ',') are:
 
 - "chromium_remote": Chromium 60 (using the remote interface)
 - "chromium": Chrome 63 (using WebDriver)
 - "firefox": Firefox 56 (using WebDriver)
 
 You can not set a specific version of the browser at runtime.
 
 Linting