use strict; use warnings;
use Test::More tests => 7;
use Graph;
my $g = Graph->new;
ok( !$g->has_vertex("a") );
ok( !$g->has_vertex("b") );
ok( !$g->has_vertex("a") );
ok( !$g->has_vertex("b") );
$g->add_vertex("a");
ok(  $g->has_vertex("a") );
ok( !$g->has_vertex("b") );
ok( !$g->has_vertex("b") );