test: cover OrmListPositionTest and teardown

test/test_orm_list_position.rb

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+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+require 'fileutils'
+
+class OrmListPositionTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-list-position-store')
+    @store = Prism::Orm::Store.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:tasks, %w[id title position deleted_at])
+    @store.create_table(:cards, %w[id title position board_id])
+
+    task_class = Class.new(Prism::Orm::Model) do
+      table_name :tasks
+      acts_as_paranoid
+      acts_as_list column: :position
+    end
+    card_class = Class.new(Prism::Orm::Model) do
+      table_name :cards
+      acts_as_list column: :position, scope: :board_id
+    end
+    plain_class = Class.new(Prism::Orm::Model) { table_name :tasks }
+
+    [task_class, card_class].each { |klass| klass.store = @store }
+    plain_class.store = @store
+    Object.const_set(:Task, task_class)
+    Object.const_set(:Card, card_class)
+    Object.const_set(:PlainTask, plain_class)
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+    %i[Task Card PlainTask].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
+  end
+
+  def test_a_model_that_never_called_acts_as_list_is_unaffected
+    refute PlainTask.acts_as_list?
+    assert Task.acts_as_list?
+  end
+
+  def test_fresh_records_are_appended_to_the_bottom_in_creation_order
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    assert_equal [1, 2, 3], [a, b, c].map(&:list_position)
+  end
+
+  def test_move_higher_swaps_with_the_previous_item_and_is_a_noop_at_the_top
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    b.move_higher
+    assert_equal 1, b.list_position
+    assert_equal 2, a.reload.list_position
+
+    b.reload.move_higher # b is already first - nothing above it to swap with
+    assert_equal 1, b.list_position
+    assert_equal 2, a.reload.list_position
+  end
+
+  def test_move_lower_swaps_with_the_next_item_and_is_a_noop_at_the_bottom
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    a.move_lower
+    assert_equal 2, a.list_position
+    assert_equal 1, b.reload.list_position
+
+    b.reload.move_lower # b is now first (pos 1), a is last (pos 2) - moving b lower swaps back
+    assert_equal 2, b.list_position
+    assert_equal 1, a.reload.list_position
+  end
+
+  def test_move_lower_on_the_last_item_is_a_noop
+    a = Task.create!(title: 'a')
+    Task.create!(title: 'b')
+    b2 = Task.find_by!(title: 'b')
+    b2.move_lower
+    assert_equal 2, b2.list_position
+    assert_equal 1, a.reload.list_position
+  end
+
+  def test_move_higher_on_the_first_item_is_a_noop
+    a = Task.create!(title: 'a')
+    Task.create!(title: 'b')
+    a.move_higher
+    assert_equal 1, a.list_position
+  end
+
+  def test_first_and_last_in_list_predicates
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    assert a.first_in_list?
+    refute a.last_in_list?
+    assert c.last_in_list?
+    refute c.first_in_list?
+    refute b.first_in_list?
+    refute b.last_in_list?
+  end
+
+  def test_move_to_top_and_move_to_bottom_reposition_and_shift_everyone_between
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    d = Task.create!(title: 'd')
+
+    c.move_to_top
+    assert_equal [1, 2, 3, 4], [c, a, b, d].map { |t| t.reload.list_position }
+
+    a.reload.move_to_bottom
+    assert_equal [1, 2, 3, 4], [c, b, d, a].map { |t| t.reload.list_position }
+  end
+
+  def test_insert_at_moves_an_item_to_an_arbitrary_middle_slot
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    d = Task.create!(title: 'd')
+
+    d.insert_at(2)
+    assert_equal [1, 2, 3, 4], [a, d, b, c].map { |t| t.reload.list_position }
+  end
+
+  def test_insert_at_on_a_record_that_is_not_persisted_raises
+    task = Task.new(title: 'unsaved')
+    assert_raises(Prism::Orm::RecordNotFound) { task.insert_at(1) }
+  end
+
+  def test_destroying_an_item_closes_the_gap_for_everyone_below_it
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    b.destroy
+    assert_equal 1, a.reload.list_position
+    assert_equal 2, c.reload.list_position
+  end
+
+  def test_soft_deleting_a_paranoid_item_also_closes_the_gap
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    b.destroy # paranoid: soft-delete, not a real row removal
+    assert b.deleted?
+    assert_equal 1, a.reload.list_position
+    assert_equal 2, c.reload.list_position
+  end
+
+  def test_restoring_a_soft_deleted_item_reappends_it_to_the_bottom_not_its_old_slot
+    a = Task.create!(title: 'a')
+    b = Task.create!(title: 'b')
+    c = Task.create!(title: 'c')
+    b.destroy
+    d = Task.create!(title: 'd')
+    assert_equal [1, 2, 3], [a.reload, c.reload, d.reload].map(&:list_position)
+
+    restored = Task.only_deleted.find_by!(title: 'b')
+    restored.restore
+    assert_equal 4, restored.list_position
+    # nobody else collides with the reappended slot
+    assert_equal [1, 2, 3, 4], [a.reload, c.reload, d.reload, restored.reload].map(&:list_position).sort
+  end
+