================================================================================
Simple Function Call
================================================================================

(output 'hi')

--------------------------------------------------------------------------------

(root
  (statement
    (expression
      (function_call
        (built_in_function
          (expression
            (value
              (string))))))))

================================================================================
Nested Function Call
================================================================================

(assert_equal (random_integer) 4)

--------------------------------------------------------------------------------

(root
  (statement
    (expression
      (function_call
        (built_in_function
          (expression
            (function_call
              (built_in_function)))
          (expression
            (value
              (integer))))))))