Failing rails test - ActionController::UnknownFormat:

I'm currently writing tests for all my controllers and have run into an issue I cannot solve. For one of my controllers, every test works (show, index, new, edit, update) but for some reason my #create test cannot pass. Just to clarify: all the fixtures and other methods run and pass fine - something is wrong with my create method or test on that method.

From what I can gather - the error may have something to do with the respond_to |format| line, but cannot seem to solve it.

Here's the test:

  test "should create captable" do
    sign_in @user
    post company_captables_url(@company, @captable), params: { captable: { company_id: @captable.company_id, name: "The BEST captable", version: @captable.version } }
    assert_response :success
  end

Here's the method from the controller:

  def create
      @captable = @company.captables.new(captable_params)

      respond_to do |format|
        if @captable.save
          format.html { redirect_to [@company, @captable], notice: 'Captable was successfully created.' }
          format.json { render :show, status: :created, location: @captable }
        else
          format.html { render :new }
          format.json { render json: @captable.errors, status: :unprocessable_entity }
        end
      end
    end

Error when running this test:

Error:
CaptablesControllerTest#test_should_create_captable:
ActionController::UnknownFormat: ActionController::UnknownFormat
    app/controllers/captables_controller.rb:24:in `create'
    test/controllers/captables_controller_test.rb:38:in `block in <class:CaptablesControllerTest>'


bin/rails test test/controllers/captables_controller_test.rb:36

Solution

From your controller, one can see it responds to both html and json.

However, in your test request, it's hitting the url without any format (see https://guides.rubyonrails.org/routing.html#path-and-url-helpers, there's no .anything at the generated urls or you'll find the .:format ending). So the controller does not know what to respond_to, throwing the Unknown Format error.

You essentially have a few options:

1) You can actually write the url and add an explicit format

2) You can try adding the format there with concatenation (ie: post "#{company_captables_url(@company, @captable)}.json")

3) You can set your routes to have a default response format (ie: resources :captables, defaults: { format: 'json' }). https://guides.rubyonrails.org/routing.html#defining-defaults