When testing: NoMethodError: undefined method `follow_redirect!'

I'm getting a NoMethodError when trying to test the redirection of a post method using 'follow_redirect!'.

This is the error:

NoMethodError:   NoMethodError: undefined method `follow_redirect!' for #<ChangePasswordsControllerTest:0x00005586ffd3c030>

Here is my controller.

def create
    @user = current_user
    if @user.authenticate(params[:user][:old_password])
      if @user.update_attributes(params.require(:user).permit(:old_password, :password, :password_confirmation))
        flash[:success] = "La contraseña se cambió correctamente"
        redirect_to membership_dashboard_path
      else
        flash[:warning] = "No se pudo cambiar la contraseña"
        render 'new'
      end
    else
      flash[:warning] = "La contraseña actual no es correcta."
      render 'new'
    end
  end 

And here is my test

test "should redirect membership dashboard if create password" do
    get :new
    post :create, params: { user: {
      old_password: '1234',
      password: "123456",
      password_confirmation: "123456" }
    }
    assert_equal 'La contraseña se cambió correctamente', flash[:success]
    assert_redirected_to membership_dashboard_path
    follow_redirect!
    assert_response :success
  end

It runs fine if I remove the last two lines

    follow_redirect!
    assert_response :success

The weirdest thing is that I'm already using 'follow_redirect!' in another test and it's fine!

Does anyone know how to fix this?