util.dbuffer: Simplify test case

An earlier theory involved the bug being related to collapsing multiple
items, so it exercised that too.

Also correct the comment, it referred to the space in "hello world" in
an earlier version before the test string was changed to "foobar", which
was what was tested in a REPL

1 files changed, 130 insertions, 0 deletions

diff --git a/spec/util_dbuffer_spec.lua b/spec/util_dbuffer_spec.lua
new file mode 100644
index 000000000..af4040423
--- /dev/null
+++ b/spec/util_dbuffer_spec.lua
@@ -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);