Calculate "inserted_count"

lib/MongoDB/InsertManyResult.pm

@@ -44,11 +44,17 @@ The number of documents inserted.
 =cut
 
 has inserted_count => (
-    is      => 'ro',
-    default => 0,
+    is      => 'lazy',
+    builder => '_build_inserted_count',
     isa => Num,
 );
 
+sub _build_inserted_count
+{
+    my ($self) = @_;
+    return scalar @{ $self->inserted };
+}
+
 =attr inserted
 
 An array reference containing information about inserted documents (if any).

t/crud.t

@@ -116,6 +116,7 @@ subtest "insert_many" => sub {
         },
         "inserted_ids contains correct keys/values"
     );
+    is($res->inserted_count, 2, "Two docs inserted.");
 
     # ordered insert should halt on error
     $coll->drop;