use Test::Leaner;
-plan tests => 7;
+plan tests => 8;
is undef, undef, 'undef is undef';
-isnt 1, undef, 'one is not undef';
-isnt undef, 1, 'undef is not one';
+isnt 0, undef, 'zero is not undef';
+isnt undef, 0, 'undef is not zero';
+is 0, 0, 'zero is zero';
is 1, 1, 'one is one';
isnt '1.0', 1, '1.0 is not one string-wise';