The test "OrganizationsControllerTest#test_0022_should allow empty array as param value of array field while updating organization" (and its LocationControllerTest equivalent) added in #17343 attempts to pass an empty array of smart_proxy_ids to the UI controller:

put :update, { :id => location.id, :location => {:organization_ids => []}}, set_session_user

In Rails 4.2.7.1 this is passed through:

[1] pry(#<OrganizationsController>)> params
=> {"organization"=>{"smart_proxy_ids"=>[]}, "id"=>"61304186", "controller"=>"organizations", "action"=>"update", "locale"=>nil}

But in Rails 5.0.1 it is missing, and causes the test for updating with an empty array to fail:

[1] pry(#<OrganizationsController>)> params
=> <ActionController::Parameters {"id"=>"61304186", "controller"=>"organizations", "action"=>"update", "locale"=>nil} permitted: false>

The test data isn't valid, as an empty array can't be represented in form encoded data.

When compared to the input generated by the Foreman UI, the multiselects generate an empty "" entry in the array to correctly pass an "empty" array through in the form data. This would generate an entry in the form data of smart_proxy_ids[]=

2017-01-19T14:12:33 709cf7eb [app] [I] Processing by OrganizationsController#update as HTML
2017-01-19T14:12:33 709cf7eb [app] [I]   Parameters: {"utf8"=>"✓", "authenticity_token"=>"[..]", "organization"=>{"parent_id"=>"", "name"=>"munge", "description"=>"", "ignore_types"=>["0",
 "0", "0", "0", "0", "0", "0", "0", "0", "0", "0"], "user_ids"=>[""], "smart_proxy_ids"=>["", "6"], "subnet_ids"=>[""], "compute_resource_ids"=>[""], "medium_ids"=>[""], "provisioning_template_ids"=>["", "60"], "ptable_ids"=>["", "102"], "domain_ids"=>[""], "realm_ids"=>[""], "environment_ids"=>[""], "hostgroup_ids"=>[""]}, "commit"=>"Submit", "id"=>"35-munge"}

The Rails 5 test framework that generates the request objects is filtering out invalid parameters when converting them internally from the hash in the test case to the form encoded version. The test data should be updated to pass an empty string as well, like the form in the real UI.