test check_implementations

lib/Boundary.pm

@@ -72,7 +72,8 @@ sub apply_interfaces_to_package {
 
 sub check_implementations {
     my ($class, $impl, @interfaces) = @_;
-    my %interface_map = %{$INFO{$impl}{interface_map}||{}};
+    return if !$INFO{$impl};
+    my %interface_map = %{$INFO{$impl}{interface_map}};
     for (@interfaces) {
         return if !$interface_map{$_}
     }

t/check_implementations.t

@@ -0,0 +1,23 @@
+use strict;
+use warnings;
+use lib 't/lib';
+use Test::More;
+
+use Boundary ();
+
+ok(!Boundary->check_implementations('Foo', 'IFoo'), 'IFoo is not yet applied as an interface of Foo.');
+
+ok(!Boundary->check_implementations('Foo', 'IFoo'), 'IFoo is not yet applied as an interface of Foo.');
+
+{
+    package Foo;
+    sub hello;
+}
+
+Boundary->apply_interfaces_to_package('Foo', 'IFoo');
+
+ok(Boundary->check_implementations('Foo', 'IFoo'), 'Foo is an implementation of IFoo');
+
+ok(!Boundary->check_implementations('Foo', 'IBar'), 'Foo is not an implementation of IBar');
+
+done_testing;