def METHOD_NAME(flask_client):
    user = login(flask_client)
    sl_domain = setup_sl_domain()
    for i in range(MAX_NB_SUBDOMAIN):
        CustomDomain.create(
            domain=f"test{i}.{sl_domain.domain}",
            user_id=user.id,
            is_sl_subdomain=True,
            commit=True,
        )
    assert CustomDomain.filter_by(user_id=user.id).count() == MAX_NB_SUBDOMAIN
    flask_client.post(
        url_for("dashboard.subdomain_route"),
        data={"form-name": "create", "subdomain": "test", "domain": sl_domain.domain},
        follow_redirects=True,
    )
    # no new subdomain is created
    assert CustomDomain.filter_by(user_id=user.id).count() == MAX_NB_SUBDOMAIN