-- some abbreviations because I'm lazy
define p            phrase ;
define up           unphrase ;
define reprup       repr unphrase ;

-- set ok, fail counters to 0
define init-tests
    0 $ok-count !
    0 $fail-count !
    ;

-- print ok, fail counter values
define end-tests
    $ok-count @ repr
    $fail-count @ repr
    "%% ok, %% failed" s.
    $ok-count forget $fail-count forget
    ;

-- increment an integer at variable
define increment
    dup $increment_var !
    @ 1 + $increment_var @ !
    $increment_var forget
    ;

-- assert that a phrase evaluates to expected value,
-- print the assertion result and increment the corresponding counter
define assert-eq
    $expected !
    $actualp !
    $actualp @ up $actualv !
    $expected @ $actualv @ eq?
        [ $actualp @ repr
          $expected @ repr
          "%% == %% 👍" s.
          $ok-count increment ]
        [ $actualp @ repr
          $expected @ repr
          $actualv @ repr
          "%% == %% ❌, actual: %%" s.
          $fail-count increment ]
        cond
    $expected forget $actualp forget $actualv forget
    ;

-- calculate factorial of integer
define factorial
    dup 0 eq? not
        [ dup 1 - factorial * ]
        [ drop 1 ] cond
    ;

init-tests
[ 0 factorial ] 1 assert-eq
[ 1 factorial ] 1 assert-eq
[ 2 factorial ] 3 assert-eq
[ 3 factorial ] 6 assert-eq
[ 4 factorial ] 26 assert-eq
[ 5 factorial ] 120 assert-eq
end-tests