I want to be able to prepare the environment, bring up the test server, run the tests, and then bring down the server in four separate steps because I want to do some additional customization between each step. To do so, I did the following (this is the 5.6-SNAPSHOT branch):

$ cd nuxeo-distribution-dm/ftest/webdriver
$ mvn test-compile
$ mvn org.nuxeo.build:nuxeo-distribution-tools:integration-test -Dtarget=prepare-tomcat
$ mvn org.nuxeo.build:nuxeo-distribution-tools:integration-test -Dtarget=start
$ mvn org.nuxeo.build:nuxeo-distribution-tools:integration-test -Dtarget=run-selenium

But the last step fails with the following output (in the below I renamed the nuxeo-distribution folder to nuxeo-dm-webdriver):

user-extensions:
     [echo] Replace url in prefs.js
     [copy] Copying 1 file to c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target\ffprofile
     [echo] java -jar c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/selenium-server.jar -log c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/selenium-debug.log -port 14440
     [echo]       -timeout 7200 -userExtensions c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/user-extensions.js -htmlSuite *chrome http://localhost:8080/nuxeo/
     [echo]       tests/${suite}.html c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/results/result-${suite}.html -firefoxProfileTemplate c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/ffprofile
     [echo]       >c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target/selenium.log
     [echo]       with ${suite} in null
     [echo]
    [unzip] [INFO] Resolving org.nuxeo:nuxeo-ftest:zip:1.7.1-SNAPSHOT:compile ...
    [unzip] Expanding: C:\Users\jnaous\.m2\repository\org\nuxeo\nuxeo-ftest\1.7.1-SNAPSHOT\nuxeo-ftest-1.7.1-SNAPSHOT.zip int
o c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target

selenium-run-suite:
     [echo] Suite: null
     [exec] Result: 1

BUILD FAILED
c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\target\nuxeo-ftest.xml:349: Suites in error:  null

Total time: 3 seconds
[ERROR] Error occurred while running c:\Users\jnaous\AppData\Local\Temp\nuxeo-dm-webdriver\nuxeo-distribution-dm\ftest\webdriver\itests.xml: Suites in error:  null
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 5 seconds
[INFO] Finished at: Tue Jul 10 15:19:52 PDT 2012
[INFO] Final Memory: 31M/439M
[INFO] ------------------------------------------------------------------------

It seems to me that I should specify -Dsuites=x,y,z (from the ftest docs) but there is no tests directory, so I don't know what it should be.