You can group related assertions in deftest unit tests within a context using the testing macro:

(deftest add-nums 
  (testing "Positive cases"
    (is (= 2 (+ 1 1)))
    (is (= 4 (+ 2 2))))
  (testing "Negative cases"
    (is (= -1 (+ 2 -3)))
    (is (= -4 (+ 8 -12)))))

This will help clarify test output when run. Note that testing must occur inside a deftest.