Since the tested function is rolls of a 7 sided die, the test numbers are magnitudes of 10x bumped up to the closest multiple of 7. This reduces spurious error from there not being an integer expected value.
my $d7 = 1..7;
sub roll7 { $d7.roll };
my $threshold = 3;
for 14, 105, 1001, 10003, 100002, 1000006 -> $n
{ dist( $n, $threshold, &roll7 ) };
sub dist ( $n is copy, $threshold, &producer ) {
my @dist;
my $expect = $n / 7;
say "Expect\t",$expect.fmt("%.3f");
loop ($_ = $n; $n; --$n) { @dist[&producer()]++; }
for @dist.kv -> $i, $v is copy {
next unless $i;
$v //= 0;
my $pct = ($v - $expect)/$expect*100;
printf "%d\t%d\t%+.2f%% %s\n", $i, $v, $pct,
($pct.abs > $threshold ?? '- skewed' !! '');
}
say '';
}