minetest/games/devtest/mods/unittests/raycast.lua

local function raycast_with_pointabilities(start_pos, end_pos, pointabilities)
	local ray = core.raycast(start_pos, end_pos, nil, nil, pointabilities)
	for hit in ray do
        if hit.type == "node" then
            return hit.under
        end
	end
    return nil
end

local function test_raycast_pointabilities(player, pos1)
    local pos2 = pos1:offset(0, 0, 1)
    local pos3 = pos1:offset(0, 0, 2)

    local oldnode1 = core.get_node(pos1)
    local oldnode2 = core.get_node(pos2)
    local oldnode3 = core.get_node(pos3)
    core.swap_node(pos1, {name = "air"})
    core.swap_node(pos2, {name = "testnodes:not_pointable"})
    core.swap_node(pos3, {name = "testnodes:pointable"})

    local p = nil
    assert(raycast_with_pointabilities(pos1, pos3, p) == pos3)

    p = core.registered_items["testtools:blocked_pointing_staff"].pointabilities
    assert(raycast_with_pointabilities(pos1, pos3, p) == nil)

    p = core.registered_items["testtools:ultimate_pointing_staff"].pointabilities
    assert(raycast_with_pointabilities(pos1, pos3, p) == pos2)

    core.swap_node(pos1, oldnode1)
    core.swap_node(pos2, oldnode2)
    core.swap_node(pos3, oldnode3)
end

unittests.register("test_raycast_pointabilities", test_raycast_pointabilities, {map=true})

local function test_raycast_noskip(_, pos)
	local function random_point_in_area(min, max)
		local extents = max - min
		local v = extents:multiply(vector.new(
			math.random(),
			math.random(),
			math.random()
		))
		return min + v
	end

	-- FIXME a variation of this unit test fails in an edge case.
	-- This is because Luanti does not handle perfectly diagonal raycasts correctly:
	-- Perfect diagonals collide with neither "outside" face and may thus "pierce" nodes.
	-- Enable the following code to reproduce:
	if 0 == 1 then
		pos = vector.new(6, 32, -3)
		math.randomseed(1596190898)
		function random_point_in_area(min, max)
			return min:combine(max, math.random)
		end
	end

	local function cuboid_minmax(extent)
		return pos:offset(-extent, -extent, -extent),
				pos:offset(extent, extent, extent)
	end

	-- Carve out a 3x3x3 dirt cuboid in a larger air cuboid
	local r = 8
	local min, max = cuboid_minmax(r + 1)
	local vm = core.get_voxel_manip(min, max)
	local old_data = vm:get_data()
	local data = vm:get_data()
	local emin, emax = vm:get_emerged_area()
	local va = VoxelArea:new({MinEdge = emin, MaxEdge = emax})
	for index in va:iterp(min, max) do
		data[index] = core.CONTENT_AIR
	end
	for index in va:iterp(cuboid_minmax(1)) do
		data[index] = core.get_content_id("basenodes:dirt")
	end
	vm:set_data(data)
	vm:write_to_map()

	-- Raycast many times from outside the cuboid
	for _ = 1, 100 do
		local ray_start
		repeat
			ray_start = random_point_in_area(cuboid_minmax(r))
		until not ray_start:in_area(cuboid_minmax(1.501))
		-- Pick a random position inside the dirt
		local ray_end = random_point_in_area(cuboid_minmax(1.499))
		-- The first pointed thing should have only air "in front" of it,
		-- or a dirt node got falsely skipped.
		local pt = core.raycast(ray_start, ray_end, false, false):next()
		if pt then
			assert(core.get_node(pt.above).name == "air")
		end
	end

	vm:set_data(old_data)
	vm:write_to_map()
end

unittests.register("test_raycast_noskip", test_raycast_noskip, {map = true, random = true})