Im using javascript I provided What the error is Showing me . It's Expeacting the wrong tail to be returNed

All tests are random, so I can't help you, especially since you're not telling me what language you're using. You probably need to change your solution.

The example Clojure tests are misleading. They will pass with the most trivial implementation (as long as the functions are defined).

(deftest example-tests
(is (head [5 1]) 6)
(is (tail [1]) [])
(is (init [1 5 7 9]) [1 5 7])
(is (last_ [7 2]) 2)
)

They should be

(deftest example-tests-fixed
(is (= (head [5 1]) 6))
(is (= (tail [1]) []))
(is (= (init [1 5 7 9]) [1 5 7]))
(is (= (last_ [7 2]) 2))
)