How do I get watir-webdriver to start Firefox 4 with Firebug?

Any ideas? I've tried setting webdriver.firefox.useExisting=true as described in the link below hoping to reuse an existing window with firebug enabled, but no such luck.

http://开发者_运维知识库code.google.com/p/selenium/wiki/FirefoxDriver

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you have to create a specific profile where Firebug is always enabled, then launch firefox with this profile in your configuration

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The quick answer is:

browser = Watir::Browser.new(:firefox, :profile => "default")

But if you are running tests you probably shouldn't use the default profile.

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profile = Selenium::WebDriver::Firefox::Profile.new
profile.add_extension "/path/to/firebug.xpi"
browser = Watir::Browser.new :firefox, :profile => profile