Content content = contentManager.addContent("key", "title", null, new JButton("Hello World!!!"), "tip");
assertNotNull(contentManager.getAliases(content));
assertEquals(0, contentManager.getAliases(content).length);
contentManager.addAlias(content, ContentManager.class);
assertEquals(1, contentManager.getAliases(content).length);
Content contentByAlias = contentManager.getContent(ContentManager.class);
assertEquals(content, contentByAlias);