Projects GitLab API: permissions.group_access doesn't work

My main aim is to find, how I can list repositories, which I’m permitted to clone?
I found List Projects API, but it looks like List Projects API response.permissions.group_access doesn’t work.

Steps to reproduce:

  1. I created a gitlab user - testUser.
  2. I created a group called group-with-developers-permissions. testUser is a member of the group with Developer role.
  3. I shared my project called testProject with group-with-developers-permissions (Max access level= Developer), so testUser can clone testProject repository - good
  4. I call gitlab rest api http:///api/v4/projects?membership=true on behalf of the testUser
    The response is:
    “id”: 1,
    “description”: “”,
    “default_branch”: “master”,

    “project_access”: null,
    “group_access”: null //why group_access is null?

Question: why permissions -> group_access is null? or how can I list repositories, which testUser is permitted to clone?

Thanks in advance for any help.