telescope.nvim/lua/tests/automated/scroller_spec.lua

local p_scroller = require('telescope.pickers.scroller')

local eq = assert.are.same

describe('scroller', function()
  local max_results = 10

  describe('ascending cycle', function()
    local cycle_scroller = p_scroller.create('cycle', 'ascending')

    it('should return values within the max results', function()
      eq(5, cycle_scroller(max_results, max_results, 5))
    end)

    it('should return 0 at 0', function()
      eq(0, cycle_scroller(max_results, max_results, 0))
    end)

    it('should cycle you to the top when you go below 0', function()
      eq(max_results - 1, cycle_scroller(max_results, max_results, -1))
    end)

    it('should cycle you to 0 when you go past the results', function()
      eq(0, cycle_scroller(max_results, max_results, max_results + 1))
    end)

    it('should cycle when current results is less than max_results', function()
      eq(0, cycle_scroller(max_results, 5, 7))
    end)
  end)

  describe('ascending limit', function()
    local limit_scroller = p_scroller.create('limit', 'ascending')

    it('should return values within the max results', function()
      eq(5, limit_scroller(max_results, max_results, 5))
    end)

    it('should return 0 at 0', function()
      eq(0, limit_scroller(max_results, max_results, 0))
    end)

    it('should not cycle', function()
      eq(0, limit_scroller(max_results, max_results, -1))
    end)

    it('should not cycle you to 0 when you go past the results', function()
      eq(max_results - 1, limit_scroller(max_results, max_results, max_results + 1))
    end)

    it('should stay at current results when current results is less than max_results', function()
      local current = 5
      eq(current - 1, limit_scroller(max_results, current, 7))
    end)
  end)

  describe('descending cycle', function()
    local cycle_scroller = p_scroller.create('cycle', 'descending')

    it('should return values within the max results', function()
      eq(5, cycle_scroller(max_results, max_results, 5))
    end)

    it('should return max_results - 1 at 0', function()
      eq(0, cycle_scroller(max_results, max_results, 0))
    end)

    it('should cycle you to the bot when you go below 0', function()
      eq(max_results - 1, cycle_scroller(max_results, max_results, -1))
    end)

    it('should cycle you to 0 when you go past the results', function()
      eq(0, cycle_scroller(max_results, max_results, max_results + 1))
    end)

    it('should cycle when current results is less than max_results', function()
      eq(9, cycle_scroller(max_results, 5, 4))
    end)
  end)

  describe('descending limit', function()
    local limit_scroller = p_scroller.create('limit', 'descending')

    it('should return values within the max results', function()
      eq(5, limit_scroller(max_results, max_results, 5))
    end)

    it('should return 0 at 0', function()
      eq(0, limit_scroller(max_results, max_results, 0))
    end)

    it('should not cycle', function()
      eq(0, limit_scroller(max_results, max_results, -1))
    end)

    it('should not cycle you to 0 when you go past the results', function()
      eq(max_results - 1, limit_scroller(max_results, max_results, max_results + 1))
    end)

    it('should stay at current results when current results is less than max_results', function()
      local current = 5
      eq(max_results - current, limit_scroller(max_results, current, 4))
    end)
  end)

  describe('https://github.com/nvim-telescope/telescope.nvim/pull/293#issuecomment-751463224', function()
    it('should handle having many more results than necessary', function()
      local scroller = p_scroller.create('cycle', 'descending')

      -- 23 112 23
      eq(0, scroller(23, 112, 23))
    end)
  end)

  describe('should give top and bottom index', function()
    it('should handle ascending', function()
      eq(0, p_scroller.top('ascending', 20, 1000))
      eq(19, p_scroller.bottom('ascending', 20, 1000))

      eq(0, p_scroller.top('ascending', 20, 10))
      eq(9, p_scroller.bottom('ascending', 20, 10))
    end)

    it('should handle descending', function()
      eq(0, p_scroller.top('descending', 20, 1000))
      eq(19, p_scroller.bottom('descending', 20, 1000))

      eq(10, p_scroller.top('descending', 20, 10))
      eq(19, p_scroller.bottom('descending', 20, 10))
    end)
  end)
end)