Adding test cases

[icy]

• [x] Public groups
• [x] Private groups
• [x] Organization private groups
• [x] Organization public groups
• [ ] Adult contents groups

[icy]

Testing for groups in Organization is now supported: https://github.com/icy/google-group-crawler/commit/54820d8023f2fb97e0c8adbf86ab31303d33a2f6 . In an Organization, there is no such thing public group

[icy]

Private groups supported: https://github.com/icy/google-group-crawler/commit/c0fff6330728393828d29d35816724cb326a5a07

[icy]

tests are working well with private groups. We haven't supported group with adult contents yet, so it's fine to close this ticket now.