With MDL-50926 fix from Tony Levi, Moodle 3.0 dev will be using phpunit 4.7+.
If you are using installed version of phpunit (not vendor/bin/phpunit), then you need to upgrade it to 4.x to run unit test for Moodle 3.0dev branch.
Testing and QA
Moodle 3.0dev has met phpunit 4.7
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