Added test for dupe parents

ensure we do not create a duplicate post/category xref for duplicate
parent categories

test/scripts/models/post.js

@@ -338,6 +338,19 @@ describe('Post', () => {
  return Post.removeById(post._id);
  }));
 
+ it('setCategories() - multiple hierarchies (dedupes repeated parent)', () => Post.insert({
+ source: 'foo.md',
+ slug: 'bar'
+ }).then(post => post.setCategories([['foo', 'bar'], ['foo', 'baz']])
+ .thenReturn(Post.findById(post._id))).then(post => {
+ var cats = post.categories.toArray();
+
+ // There should have been 3 categories set (foo is dupe)
+ cats.should.have.lengthOf(3);
+
+ return Post.removeById(post._id);
+ }));
+
  it('remove PostTag references when a post is removed', () => Post.insert({
  source: 'foo.md',
  slug: 'bar'