--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spec/util_dbuffer_spec.lua	Mon Aug 24 17:28:48 2020 +0200
@@ -0,0 +1,130 @@
+local dbuffer = require "util.dbuffer";
+describe("util.dbuffer", function ()
+	describe("#new", function ()
+		it("has a constructor", function ()
+			assert.Function(dbuffer.new);
+		end);
+		it("can be created", function ()
+			assert.truthy(dbuffer.new());
+		end);
+		it("won't create an empty buffer", function ()
+			assert.falsy(dbuffer.new(0));
+		end);
+		it("won't create a negatively sized buffer", function ()
+			assert.falsy(dbuffer.new(-1));
+		end);
+	end);
+	describe(":write", function ()
+		local b = dbuffer.new();
+		it("works", function ()
+			assert.truthy(b:write("hi"));
+		end);
+	end);
+
+	describe(":read", function ()
+		it("supports optional bytes parameter", function ()
+			-- should return the frontmost chunk
+			local b = dbuffer.new();
+			assert.truthy(b:write("hello"));
+			assert.truthy(b:write(" "));
+			assert.truthy(b:write("world"));
+			assert.equal("h", b:read(1));
+
+			assert.equal("ello", b:read());
+			assert.equal(" ", b:read());
+			assert.equal("world", b:read());
+		end);
+	end);
+
+	describe(":discard", function ()
+		local b = dbuffer.new();
+		it("works", function ()
+			assert.truthy(b:write("hello world"));
+			assert.truthy(b:discard(6));
+			assert.equal(5, b:length());
+			assert.equal("world", b:read(5));
+		end);
+	end);
+
+	describe(":collapse()", function ()
+		it("works on an empty buffer", function ()
+			local b = dbuffer.new();
+			b:collapse();
+		end);
+	end);
+
+	describe(":sub", function ()
+		-- Helper function to compare buffer:sub() with string:sub()
+		local s = "hello world";
+		local function test_sub(b, x, y)
+			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 = dbuffer.new();
+			assert.truthy(b:write("hello world"));
+			assert.equals("hello", b:sub(1, 5));
+		end);
+
+		it("works after discard", function ()
+			local b = dbuffer.new(256);
+			assert.truthy(b:write("foobar"));
+			assert.equals("foobar", b:sub(1, 6));
+			assert.truthy(b:discard(3)); -- consume "foo"
+			assert.equals("bar", b:sub(1, 3));
+		end);
+
+		it("supports optional end parameter", function ()
+			local b = dbuffer.new();
+			assert.truthy(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 = dbuffer.new(11);
+			assert.truthy(b:write(s));
+			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 s = "hello world"
+		local function test_byte(b, x, y)
+			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 = dbuffer.new(11);
+			assert.truthy(b:write(s));
+			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);
+
+		it("works with characters > 127", function ()
+			local b = dbuffer.new();
+			b:write(string.char(0, 140));
+			local r = { b:byte(1, 2) };
+			assert.same({ 0, 140 }, r);
+		end);
+
+		it("works on an empty buffer", function ()
+			local b = dbuffer.new();
+			assert.equal("", b:sub(1,1));
+		end);
+	end);
+end);