+ is($lse->kw_changed($eml, [qw(answered seen)]), 0,
+ 'kw_changed false when unchanged');
+ is($lse->kw_changed($eml, [qw(answered seen flagged)]), 1,
+ 'kw_changed true when +flagged');
+ is($lse->kw_changed(eml_load('t/plack-qp.eml'), ['seen']), undef,
+ 'kw_changed undef on unknown message');