Tests not passing on clean clone?

Very possibly my issue in setting up the source code, but stumped. Running the test server on a clean clone, a few tests don't pass on Mac OS 10.8:

• Chrome: 1582 of 1589 pass, 7 failed
• Safari: 1570 tests of 1589 passed, 19 failed.
• Firefox: 1570 tests of 1589 passed, 19 failed.

The failing tests looks minor, just enough to complicate a clean pull request on an unrelated aspect:

Polling: Basic polling non overlapping through dataset api (5, 13, 18)Rerun
failed
Expected:   "98_key"
Result:     "98_value"
Diff:   "98_key" "98_value" 
Source:     .fetch/<.success<@http://localhost:9292/src/dataset.js:177

this one may be nondeterministic, as the expected and result values are different each time the tests are run, and usually very closely similar, just not exactly same:

Polling: Polling with unique constraint for updates (12, 20, 32)
failed
Expected:   977
Result:     978
Diff:   977 978 
Source:     .fetch/<.success<@http://localhost:9292/src/dataset.js:177