describe(":sub", function ()

		-- Helper function to compare buffer:sub() with string:sub()

		local function test_sub(b, x, y)

			local s = b:read(#b, true);

			local string_result, buffer_result = s:sub(x, y), b:sub(x, y);

			assert.equals(string_result, buffer_result, ("buffer:sub(%d, %s) does not match string:sub()"):format(x, y and ("%d"):format(y) or "nil"));

		end

		it("works", function ()

			local b = rb.new();

			b:write("hello world");

			assert.equals("hello", b:sub(1, 5));

		end);

		it("supports optional end parameter", function ()

			local b = rb.new();

			b:write("hello world");

			assert.equals("hello world", b:sub(1));

			assert.equals("world", b:sub(-5));

		end);

		it("is equivalent to string:sub", function ()

			local b = rb.new(6);

			b:write("foobar");

			b:read(3);

			b:write("foo");

			for i = -13, 13 do

				for j = -13, 13 do

					test_sub(b, i, j);

				end

			end

		end);

	end);

	describe(":byte", function ()

		-- Helper function to compare buffer:byte() with string:byte()

		local function test_byte(b, x, y)

			local s = b:read(#b, true);

			local string_result, buffer_result = {s:byte(x, y)}, {b:byte(x, y)};

			assert.same(string_result, buffer_result, ("buffer:byte(%d, %s) does not match string:byte()"):format(x, y and ("%d"):format(y) or "nil"));

		end

		it("is equivalent to string:byte", function ()

			local b = rb.new(6);

			b:write("foobar");

			b:read(3);

			b:write("foo");

			test_byte(b, 1);

			test_byte(b, 3);

			test_byte(b, -1);

			test_byte(b, -3);

			for i = -13, 13 do

				for j = -13, 13 do

					test_byte(b, i, j);

				end

			end

		end);

	end);