Code like this should create user with assigned ID and searching by this user should return same user:

User newUser = new User(username);
identityManager.add(newUser);

User searchedUser = BasicModel.getUser(username);
Assert.assertEquals(newUser.getId(), searchedUser.getId());

In Active Directory, the specified Assert doesn't work. newUser doesn't have correct ID assigned due to method LDAPIdentityStore.getEntryIdentifier, which doesn't correctly parse ID from Active Directory in byte[] format. It should use:

this.operationManager.decodeEntryUUID(id.get()) 

similarly like LDAPIdentityStore.populateAttributedType .