(begin
  (displayln "--- TEST: boolean? ---------------------------------------------")
  (displayln (boolean? +))
  (displayln (boolean? '()))
  (displayln (boolean? #true))
  (displayln (boolean? #false))
  ;(displayln (boolean? #\n))
  (displayln (boolean? 'foo))
  (displayln (boolean? "foo"))
  (displayln (boolean? 123))
  (displayln (boolean? (cons 123 456)))
  (newline)
  (displayln "--- TEST: char? ------------------------------------------------")
  (displayln (char? +))
  (displayln (char? '()))
  (displayln (char? #true))
  (displayln (char? #false))
  ;(displayln (char? #\n))
  (displayln (char? 'foo))
  (displayln (char? "foo"))
  (displayln (char? 123))
  (displayln (char? (cons 123 456)))
  (newline)
  (displayln "--- TEST: null? ------------------------------------------------")
  (displayln (null? +))
  (displayln (null? '()))
  (displayln (null? #true))
  (displayln (null? #false))
  ;(displayln (null? #\n))
  (displayln (null? 'foo))
  (displayln (null? "foo"))
  (displayln (null? 123))
  (displayln (null? (cons 123 456)))
  (newline)
  (displayln "--- TEST: number? ----------------------------------------------")
  (displayln (number? +))
  (displayln (number? '()))
  (displayln (number? #true))
  (displayln (number? #false))
  ;(displayln (number? #\n))
  (displayln (number? 'foo))
  (displayln (number? "foo"))
  (displayln (number? 123))
  (displayln (number? (cons 123 456)))
  (newline)
  (displayln "--- TEST: pair? ------------------------------------------------")
  (displayln (pair? +))
  (displayln (pair? '()))
  (displayln (pair? #true))
  (displayln (pair? #false))
  ;(displayln (pair? #\n))
  (displayln (pair? 'foo))
  (displayln (pair? "foo"))
  (displayln (pair? 123))
  (displayln (pair? (cons 123 456)))
  (newline)
  (displayln "--- TEST: procedure? -------------------------------------------")
  (displayln (procedure? +))
  (displayln (procedure? '()))
  (displayln (procedure? #true))
  (displayln (procedure? #false))
  ;(displayln (procedure? #\n))
  (displayln (procedure? 'foo))
  (displayln (procedure? "foo"))
  (displayln (procedure? 123))
  (displayln (procedure? (cons 123 456)))
  (newline)
  (displayln "--- TEST: string? ----------------------------------------------")
  (displayln (string? +))
  (displayln (string? '()))
  (displayln (string? #true))
  (displayln (string? #false))
  ;(displayln (string? #\n))
  (displayln (string? 'foo))
  (displayln (string? "foo"))
  (displayln (string? 123))
  (displayln (string? (cons 123 456)))
  (newline)
  (displayln "--- TEST: symbol? ----------------------------------------------")
  (displayln (symbol? +))
  (displayln (symbol? '()))
  (displayln (symbol? #true))
  (displayln (symbol? #false))
  ;(displayln (symbol? #\n))
  (displayln (symbol? 'foo))
  (displayln (symbol? "foo"))
  (displayln (symbol? 123))
  (displayln (symbol? (cons 123 456)))
)