Back to Repositories

Testing Pagination Tag Generation Workflow in Kaminari

This test suite validates the pagination tag generation functionality in Kaminari, focusing on how different page ranges and window sizes affect the rendered navigation elements. It implements a custom TagSpy class to track instantiated pagination components and verify correct tag sequencing.

Test Coverage Overview

The test suite provides comprehensive coverage of pagination tag generation scenarios:

Single page navigation testing
Multi-page navigation with varying window sizes
Edge cases for first/last page handling
Gap insertion logic between page ranges

Implementation Analysis

The testing approach utilizes a custom TagSpy class that extends Kaminari::Helpers::Paginator to track generated navigation elements. It implements specialized tag detection for first_page, prev_page, next_page, last_page, and gap components through metaprogramming techniques.

Technical Details

Key technical components include:

ActionView::TestCase integration
Dynamic tag generation through eval
Custom paginator_class implementation
User model fixtures for pagination testing

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases with proper teardown
Comprehensive edge case coverage
DRY helper methods for test setup
Clear test case organization using sub_test_case blocks

kaminari/kaminari

kaminari-core/test/helpers/paginator_tags_test.rb

            
# frozen_string_literal: true

require 'test_helper'

if defined? ::Kaminari::Actionview
  class PaginatorTagsTest < ActionView::TestCase
    # A test paginator that can detect instantiated tags inside
    class TagSpy < Kaminari::Helpers::Paginator
      def initialize(*, **)
        super
        @tags = []
      end

      def page_tag(page)
        @tags << page.to_i
        super
      end

      %w[first_page prev_page next_page last_page gap].each do |tag|
        eval <<-DEF, nil, __FILE__, __LINE__ + 1
          def #{tag}_tag
            @tags << :#{tag}
            super
          end
        DEF
      end

      def partial_path
        'kaminari/paginator'
      end

      def to_s
        super
        @tags
      end
    end

    def tags_for(collection, window: 4, outer_window: 0)
      view.paginate(collection, paginator_class: TagSpy, window: window, outer_window: outer_window, params: {controller: 'users', action: 'index'})
    end

    teardown do
      User.delete_all
    end

    test '1 page in total' do
      3.times {|i| User.create! name: "user#{i}"}
      assert_empty tags_for(User.page(1).per(3))
    end

    sub_test_case 'when having 1 outer_window (and 1 inner window)' do
      def tags_for(collection, window: 1, outer_window: 1)
        super
      end

      test '10 pages in total' do
        20.times {|i| User.create! name: "user#{i}"}

        assert_equal [1, 2, :gap, 10, :next_page, :last_page], tags_for(User.page(1).per(2))
        assert_equal [:first_page, :prev_page, 1, 2, 3, :gap, 10, :next_page, :last_page], tags_for(User.page(2).per(2))
        assert_equal [:first_page, :prev_page, 1, 2, 3, 4, :gap, 10, :next_page, :last_page], tags_for(User.page(3).per(2))
        # the 3rd page doesn't become a gap because it's a single gap
        assert_equal [:first_page, :prev_page, 1, 2, 3, 4, 5, :gap, 10, :next_page, :last_page], tags_for(User.page(4).per(2))
        assert_equal [:first_page, :prev_page, 1, :gap, 4, 5, 6, :gap, 10, :next_page, :last_page], tags_for(User.page(5).per(2))
        assert_equal [:first_page, :prev_page, 1, :gap, 5, 6, 7, :gap, 10, :next_page, :last_page], tags_for(User.page(6).per(2))
        # the 9th page doesn't become a gap because it's a single gap
        assert_equal [:first_page, :prev_page, 1, :gap, 6, 7, 8, 9, 10, :next_page, :last_page], tags_for(User.page(7).per(2))
        assert_equal [:first_page, :prev_page, 1, :gap, 7, 8, 9, 10, :next_page, :last_page], tags_for(User.page(8).per(2))
        assert_equal [:first_page, :prev_page, 1, :gap, 8, 9, 10, :next_page, :last_page], tags_for(User.page(9).per(2))
        assert_equal [:first_page, :prev_page, 1, :gap, 9, 10], tags_for(User.page(10).per(2))
      end
    end
  end
end