title: How to set the firefox binary in Serenity (previous to geckodriver)?
body: <p>I'm using the serenity 1.1.42 version and I would like to run my test cases in different versions of Firefox. To do that, I try to set where is the Firefox binary file, because I'm using Mac OS, but serenity always starts with the default installed version on mi computer, the last.</p>
  
  <p>What I have tried? I put into the <code>serenity.properties</code> file this different combinations:</p>
  
  <pre><code>webdriver.firefox.driver=/Users/myuser/Applications/Firefox55.app/Contents/MacOS/firefox-bin
  </code></pre>
  
  <p>In other execution:</p>
  
  <pre><code>webdriver.firefox.preferences="firefox.binary=/Users/myuser/Applications/Firefox55.app/Contents/MacOS/firefox-bin"
  </code></pre>
  
  <p>In other execution:</p>
  
  <pre><code>webdriver.driver=/Users/myuser/Applications/Firefox55.app/Contents/MacOS/firefox-bin
  </code></pre>
  
  <p>In one more execution:</p>
  
  <pre><code>webdriver.firefox.bin=/Users/myuser/Applications/Firefox55.app/Contents/MacOS/firefox-bin
  </code></pre>
  
  <p>But no one of this configurations worked for me. How should I configure the <code>serenity.properties</code> file to run my own version of Firefox?</p>
  
  <p>Thank you in advance.</p>