: test-string-length ( -- )
    "hello" string.length
    5 test.assert-eq
;

: test-string-concat ( -- )
    "hello" " world" string.concat
    "hello world" string.equal? test.assert
;

: test-string-empty ( -- )
    "" string.empty?
    test.assert
;

: test-string-not-empty ( -- )
    "hi" string.empty?
    not test.assert
;
