use strict;
use Test::More tests => 7;
use Graph;
my $g = Graph->new;
ok( !$g->has_vertices() );
my $v = $g->vertices;
is( $v, 0 );
my @v = $g->vertices;
is( "@v", "" );
$g->add_vertex("a");
$v = $g->vertices;
is( $v, 1 );
@v = $g->vertices;
is( "@v", "a" );
$g->add_vertex("b");
$v = $g->vertices;
is( $v, 2 );
@v = sort $g->vertices;
is( "@v", "a b" );