Hi, I see that your working towards supporting draft-06, so I thought I'd try to help.
The first test failure I had was:
1) JsonSchema\Tests\Constraints\FormatTest::testValidFormat with data set #10 ('2000-05-01T12:12:12+0100', 'date-time')
Failed asserting that an array is empty.
I tracked this down to:
yield ['2000-05-01T12:12:12+0100', 'date-time'];
in the getValidFormats method, which appears to be an invalid format for RFC3339.
I've opened a pull request to remove that line, please do close this issue (and I'll close the pull request), if I am wrong.
Best!