the log contains "No tests run or test summary not found". perhaps some files describing what tests to run are not available to the test harness? the builds below were run against the same source revision. one is an artifact build the other is normal. failure example (against artifact build): https://treeherder.mozilla.org/#/jobs?repo=try&revision=a87f3bbb1d92719f77806a8e4967363c206333c1&filter-tier=1&filter-tier=2&filter-tier=3&group_state=expanded&exclusion_profile=false&filter-searchStr=cppunit success example (against normal build): https://treeherder.mozilla.org/#/jobs?repo=try&revision=a2809cdc540d9bb19ed13861e36d9d60547108fc&filter-tier=1&filter-tier=2&filter-tier=3&group_state=expanded&exclusion_profile=false&filter-searchStr=cppunit

Quite a few of our tests are known to fail against an artifact build, these are going to have limited effectiveness for greening things up for now. More details in bug 1278699.