title: minitest controller testing failure
body: <p>I'm experiencing trouble to test controller with minitest. My problem just in the following case - when I'm attempting to delete record. Controller is just basic scaffold in namespace <code>admin</code>, but test is below:</p>
  
  <pre><code>require 'test_helper'
  
  describe Admin::ProvidersController do
  
    let(:provider) { FactoryGirl.create(:provider) }
  
    it "gets index" do
      get :index
      assert_response :success
      assert_not_nil assigns(:providers)
    end
  
    it "gets new" do
      get :new
      assert_response :success
    end
  
    it "creates provider" do
      assert_difference('Provider.count') do
        post :create, provider: { description: 'Description', name: 'Name' }
      end
  
      assert_redirected_to admin_provider_path(assigns(:provider))
    end
  
    it "shows provider" do
      get :show, id: provider
      assert_response :success
    end
  
    it "gets edit" do
      get :edit, id: provider
      assert_response :success
    end
  
    it "updates provider" do
      put :update, id: provider, provider: { description: 'New description', name: 'New name' }
      assert_redirected_to admin_provider_path(assigns(:provider))
    end
  
    it "destroys provider" do
      assert_difference('Provider.count', -1, 'An Provider should be destroyed') do
        delete :destroy, id: provider
      end
  
      assert_redirected_to admin_providers_path
    end
  
  end
  </code></pre>
  
  <p>on <code>rake test:controllers</code> I see:</p>
  
  <pre><code>Started
  
  Admin::ProvidersController
    test_0001_gets index                                            PASS (0.12s)
    test_0002_gets new                                              PASS (0.17s)
    test_0003_creates provider                                      PASS (0.01s)
    test_0004_shows provider                                        PASS (0.04s)
    test_0005_gets edit                                             PASS (0.05s)
    test_0006_updates provider                                      PASS (0.01s)
  0
  0
    test_0007_destroys provider                                     FAIL (0.02s)
  Minitest::Assertion:         An Provider should be destroyed.
          "Provider.count" didn't change by -1.
          Expected: -1
            Actual: 0
          /Users/alec/.rvm/gems/ruby-2.1.1@lorgnette/gems/activesupport-4.1.1/lib/active_support/testing/assertions.rb:76:in `block in assert_difference'
          /Users/alec/.rvm/gems/ruby-2.1.1@lorgnette/gems/activesupport-4.1.1/lib/active_support/testing/assertions.rb:73:in `each'
          /Users/alec/.rvm/gems/ruby-2.1.1@lorgnette/gems/activesupport-4.1.1/lib/active_support/testing/assertions.rb:73:in `each_with_index'
          /Users/alec/.rvm/gems/ruby-2.1.1@lorgnette/gems/activesupport-4.1.1/lib/active_support/testing/assertions.rb:73:in `assert_difference'
          /Users/alec/Documents/Projects/RubyApps/lorgnette/test/controllers/admin/providers_controller_test.rb:42:in `block (2 levels) in &lt;top (required)&gt;'
  
  
  Fabulous run in 0.43316s
  7 tests, 11 assertions, 1 failures, 0 errors, 0 skips
  </code></pre>
  
  <p>in logs I see:</p>
  
  <pre><code>-------------------------------------------------------
  Admin::ProvidersController: test_0007_destroys provider
  -------------------------------------------------------
     (0.4ms)  SELECT COUNT(*) FROM "providers"
     (0.3ms)  SELECT COUNT(*) FROM "providers"
     (0.2ms)  SAVEPOINT active_record_1
    SQL (0.4ms)  INSERT INTO "providers" ("created_at", "description", "name", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id"  [["created_at", "2014-05-30 23:06:43.102303"], ["description", "MyText"], ["name", "MyString"], ["updated_at", "2014-05-30 23:06:43.102303"]]
     (0.2ms)  RELEASE SAVEPOINT active_record_1
  Processing by Admin::ProvidersController#destroy as HTML
    Parameters: {"id"=&gt;"271"}
    Provider Load (0.4ms)  SELECT  "providers".* FROM "providers"  WHERE "providers"."id" = $1 LIMIT 1  [["id", 271]]
     (0.2ms)  SAVEPOINT active_record_1
    SQL (0.3ms)  DELETE FROM "providers" WHERE "providers"."id" = $1  [["id", 271]]
     (0.1ms)  RELEASE SAVEPOINT active_record_1
  Redirected to http://test.host/admin/providers
  Completed 302 Found in 3ms (ActiveRecord: 0.9ms)
     (0.3ms)  SELECT COUNT(*) FROM "providers"
     (0.2ms)  SELECT COUNT(*) FROM "providers"
     (0.5ms)  ROLLBACK
  </code></pre>
  
  <p>What's wrong with delete test?</p>