Add a test suite for the shipped extensions

13 files changed, 1582 insertions, 0 deletions

diff --git a/tests/extensions/fake-lexers/lexer.lua b/tests/extensions/fake-lexers/lexer.lua
new file mode 100644
index 0000000..adf7d5b
--- /dev/null
+++ b/tests/extensions/fake-lexers/lexer.lua
@@ -0,0 +1,77 @@
+-- A miniature stand-in for the Scintillua lexer module, just enough for the
+-- syntax-highlight checks to drive every path through the filter without the
+-- real collection installed. load() hands out one of the toy lexers below by
+-- name and detect() recognises a single filename suffix, so a check can tell
+-- the detection path apart from the extension path by which lexer ends up
+-- running. Anything the filter treats as optional, a lexer that will not
+-- load or one that raises while lexing, has a name here too.
+
+local M = {}
+
+-- Tokens come back the way Scintillua returns them, one flat list of a tag
+-- name and the position just past the token it names. Letter runs are
+-- keywords, digit runs are numbers, a single quoted run carries a dotted tag
+-- so the dotted first component lookup gets exercised, and any other byte is
+-- whitespace, which maps to no css class.
+local function lex_words(self, text)
+	local tokens = {}
+	local pos = 1
+	while pos <= #text do
+		local start, stop = text:find("^%a+", pos)
+		if not start then
+			start, stop = text:find("^%d+", pos)
+			if start then
+				tokens[#tokens + 1] = "number"
+			else
+				start, stop = text:find("^'[^']*'", pos)
+				if start then
+					tokens[#tokens + 1] = "string.double"
+				else
+					stop = pos
+					tokens[#tokens + 1] = "whitespace"
+				end
+			end
+		else
+			tokens[#tokens + 1] = "keyword"
+		end
+		tokens[#tokens + 1] = stop + 1
+		pos = stop + 1
+	end
+	return tokens
+end
+
+-- Tags only the first four bytes and stops, so the filter has to append the
+-- untagged tail itself or the check for it fails.
+local function lex_short(self, text)
+	if #text < 5 then
+		return {}
+	end
+	return { "keyword", 5 }
+end
+
+local function lex_raise(self, text)
+	error("this lexer always raises")
+end
+
+local lexers = {
+	fake = { lex = lex_words },
+	short = { lex = lex_short },
+	badlex = { lex = lex_raise },
+}
+
+function M.load(name)
+	local lexer = lexers[name]
+	if lexer == nil then
+		error("no fake lexer named " .. tostring(name))
+	end
+	return lexer
+end
+
+function M.detect(filename)
+	if filename:match("%.viadetect$") then
+		return "fake"
+	end
+	return nil
+end
+
+return M
diff --git a/tests/extensions/harness.lua b/tests/extensions/harness.lua
new file mode 100644
index 0000000..9085010
--- /dev/null
+++ b/tests/extensions/harness.lua
@@ -0,0 +1,268 @@
+-- Stand-in for cgit's Lua filter host, dofiled by the test-*.lua files beside
+-- it and returning a table of helpers. It provides the html output sinks with
+-- the same escaping source/html.c performs, collects everything a filter
+-- emits so a check can look at the finished piece of page, and carries the
+-- check bookkeeping whose result the t05xx scripts read as the exit code.
+
+local harness = {}
+
+local pieces = {}
+
+-- cgit hands a sink's argument to lua_tostring, which turns a number into
+-- digits and anything else into no output at all, and the C side then
+-- measures the string with strlen, so everything from the first NUL byte on
+-- is dropped. Both behaviours are kept here because the extensions document
+-- the truncation and a test has to prove it rather than pass the bytes
+-- through.
+local function sink(escape)
+	return function(value)
+		if type(value) == "number" then
+			value = tostring(value)
+		elseif type(value) ~= "string" then
+			return
+		end
+		local nul = value:find("\0", 1, true)
+		if nul then
+			value = value:sub(1, nul - 1)
+		end
+		if escape then
+			value = escape(value)
+		end
+		pieces[#pieces + 1] = value
+	end
+end
+
+local txt_map = { ["&"] = "&amp;", ["<"] = "&lt;", [">"] = "&gt;" }
+local attr_map = {
+	["&"] = "&amp;", ["<"] = "&lt;", [">"] = "&gt;",
+	["'"] = "&#x27;", ['"'] = "&quot;",
+}
+
+html = sink(nil)
+html_txt = sink(function(s)
+	return (s:gsub("[&<>]", txt_map))
+end)
+html_attr = sink(function(s)
+	return (s:gsub("[&<>'\"]", attr_map))
+end)
+
+-- No shipped extension calls the remaining sinks, so rather than risk an
+-- unfaithful copy quietly passing a test, using one fails loudly until its
+-- escaping is mirrored from source/html.c the way the three above are.
+local function unmirrored(name)
+	return function()
+		error(name .. " is not mirrored by the test harness yet")
+	end
+end
+
+html_url_path = unmirrored("html_url_path")
+html_url_arg = unmirrored("html_url_arg")
+html_include = unmirrored("html_include")
+
+function harness.reset()
+	pieces = {}
+end
+
+function harness.output()
+	return table.concat(pieces)
+end
+
+function harness.load(script)
+	dofile(script)
+end
+
+local unpack_args = unpack or table.unpack
+
+-- One whole filter round trip, an open with the given arguments, a write per
+-- string and the close, returning the collected output and the close's
+-- answer.
+function harness.run(args, writes)
+	harness.reset()
+	filter_open(unpack_args(args or {}))
+	for _, text in ipairs(writes or {}) do
+		filter_write(text)
+	end
+	local ret = filter_close()
+	return harness.output(), ret
+end
+
+-- Loaders registered here win over any real module on the package path, so a
+-- test can hand a script a deterministic stand-in, or with a failing loader
+-- prove the script's fallback for a module that is not installed.
+function harness.preload(name, module)
+	package.preload[name] = function()
+		return module
+	end
+end
+
+function harness.preload_failure(name)
+	package.preload[name] = function()
+		error(name .. " deliberately unavailable in this test")
+	end
+end
+
+-- Redirect chosen absolute paths to fixtures in the test directory, for the
+-- scripts that read configuration from fixed locations like /etc.
+local path_map = nil
+
+function harness.redirect_file(from, to)
+	if path_map == nil then
+		path_map = {}
+		local real_open = io.open
+		io.open = function(path, mode)
+			return real_open(path_map[path] or path, mode)
+		end
+	end
+	path_map[from] = to
+end
+
+-- Deterministic bytes standing in for a digest, built from djb2 style lanes
+-- in plain arithmetic so they compute the same on every Lua version. Not
+-- remotely cryptographic, and enough for what the checks assert, that equal
+-- input hashes equal, different input hashes different and a tampered
+-- payload no longer verifies.
+local function fake_digest_bytes(text)
+	local lanes = { 5381, 52711, 1313, 7919 }
+	for i = 1, #text do
+		local byte = text:byte(i)
+		for j = 1, 4 do
+			lanes[j] = (lanes[j] * 33 + byte + j) % 4294967296
+		end
+	end
+	local bytes = {}
+	for j = 1, 4 do
+		local value = lanes[j]
+		for _ = 1, 4 do
+			bytes[#bytes + 1] = string.char(value % 256)
+			value = math.floor(value / 256)
+		end
+	end
+	return table.concat(bytes)
+end
+
+harness.fake_digest_bytes = fake_digest_bytes
+
+-- The slice of the luaossl digest interface the avatar filters use.
+function harness.stub_digest()
+	harness.preload("openssl.digest", {
+		new = function(algorithm)
+			return {
+				final = function(self, text)
+					return fake_digest_bytes(algorithm .. "\0" .. text)
+				end,
+			}
+		end,
+	})
+end
+
+-- crypt(3) reuses the salt fields of the setting it is handed and appends a
+-- hash of the password, so this stand-in keeps the fields and appends the
+-- password itself. A stored value of the salt fields plus the password then
+-- verifies exactly when the password matches, which is all the login checks
+-- need.
+local function fake_crypt(password, setting)
+	local prefix = setting:match("^(%$[^$]+%$[^$]+%$[^$]*%$)")
+	if prefix == nil then
+		prefix = setting .. "$"
+	end
+	return prefix .. password
+end
+
+harness.fake_crypt = fake_crypt
+
+-- The slices of luaossl and luaposix the auth filters use. The link and
+-- unlink stubs serve the secret creation path, which the auth checks bypass
+-- by replacing get_secret, so they only have to exist.
+function harness.stub_auth_modules()
+	local rand_counter = 0
+	harness.preload("posix.sys.stat", {
+		umask = function(mask)
+			return 18
+		end,
+	})
+	harness.preload("posix.unistd", {
+		crypt = fake_crypt,
+		link = function(from, to)
+			return nil
+		end,
+		unlink = function(path)
+			os.remove(path)
+			return 0
+		end,
+	})
+	harness.preload("openssl.rand", {
+		bytes = function(count)
+			local out = {}
+			for i = 1, count do
+				rand_counter = rand_counter + 1
+				out[i] = string.char((rand_counter * 37 + 11) % 256)
+			end
+			return table.concat(out)
+		end,
+	})
+	harness.preload("openssl.hmac", {
+		new = function(key, algorithm)
+			return {
+				final = function(self, payload)
+					return fake_digest_bytes(key .. "\1" ..
+						algorithm .. "\1" .. payload)
+				end,
+			}
+		end,
+	})
+end
+
+local checks = 0
+local failures = 0
+
+local function fail(name, detail)
+	failures = failures + 1
+	io.write("failed check ", name, "\n")
+	if detail then
+		io.write(detail, "\n")
+	end
+end
+
+function harness.check(name, ok, detail)
+	checks = checks + 1
+	if not ok then
+		fail(name, detail)
+	end
+end
+
+function harness.equals(name, got, want)
+	checks = checks + 1
+	if got ~= want then
+		fail(name, "wanted " .. tostring(want) ..
+			"\n   got " .. tostring(got))
+	end
+end
+
+function harness.contains(name, haystack, needle)
+	checks = checks + 1
+	if type(haystack) ~= "string"
+	    or not haystack:find(needle, 1, true) then
+		fail(name, "wanted " .. needle ..
+			"\nwithin " .. tostring(haystack))
+	end
+end
+
+function harness.excludes(name, haystack, needle)
+	checks = checks + 1
+	if type(haystack) ~= "string"
+	    or haystack:find(needle, 1, true) then
+		fail(name, "did not want " .. needle ..
+			"\nwithin " .. tostring(haystack))
+	end
+end
+
+function harness.finish()
+	if failures > 0 then
+		io.write(failures, " of ", checks, " checks failed\n")
+		os.exit(1)
+	end
+	io.write("passed ", checks, " checks\n")
+	os.exit(0)
+end
+
+return harness
diff --git a/tests/extensions/lib.sh b/tests/extensions/lib.sh
new file mode 100644
index 0000000..1b31a4b
--- /dev/null
+++ b/tests/extensions/lib.sh
@@ -0,0 +1,70 @@
+# Shared groundwork for the t05xx scripts, sourced after setup.sh from inside
+# the trash directory. It locates the shipped extensions and the unit checks
+# beside this file, finds the standalone Lua interpreters the checks can run
+# under, and offers a probe that asks the Lua inside the cgit binary itself
+# whether a module is available to it, since that interpreter can differ from
+# every standalone one on the path.
+
+EXTENSIONS_DIRECTORY=$(cd "$TEST_OUTPUT_DIRECTORY/../custom/extensions" && pwd)
+EXT_TEST_DIRECTORY=$(cd "$TEST_OUTPUT_DIRECTORY/extensions" && pwd)
+
+# Prints the Lua version a binary reports, like 5.1, which is also what
+# LuaJIT reports.
+ext_lua_version() {
+	"$1" -e 'io.write(string.match(_VERSION, "%d+%.%d+"))' 2>/dev/null
+}
+
+# Prints the interpreters found on the path whose version falls between 5.1
+# and the given 5.x ceiling, one per line, since each extension states the
+# versions it runs on and a test must not fail a script on a version it never
+# claimed.
+ext_lua_interpreters() {
+	ext_lua_ceiling=$1
+	for ext_lua_bin in luajit lua5.1 lua5.2 lua5.3 lua5.4 lua5.5 lua
+	do
+		command -v "$ext_lua_bin" >/dev/null 2>&1 || continue
+		case "$(ext_lua_version "$ext_lua_bin")" in
+		5.[1-9])
+			ext_lua_minor=$(ext_lua_version "$ext_lua_bin")
+			ext_lua_minor=${ext_lua_minor#5.}
+			test "$ext_lua_minor" -le "$ext_lua_ceiling" &&
+				echo "$ext_lua_bin"
+			;;
+		esac
+	done
+}
+
+# Asks whether cgit's own Lua can require every module named, by pointing a
+# throwaway commit-filter at the given repository and reading its answer off
+# the rendered commit page. Filters need a page to run on, which is why a
+# repository has to be handed in.
+cgit_lua_probe() {
+	test "$CGIT_HAS_LUA" -eq 1 || return 1
+	cgit_lua_probe_gitdir=$1
+	shift
+	{
+		echo "function filter_open(...) end"
+		echo "function filter_write(str) end"
+		echo "function filter_close()"
+		echo "	local ok = true"
+		for cgit_lua_probe_module in "$@"
+		do
+			echo "	if not pcall(require, '$cgit_lua_probe_module') then"
+			echo "		ok = false"
+			echo "	end"
+		done
+		echo "	if ok then html('LUA_PROBE_YES') else html('LUA_PROBE_NO') end"
+		echo "	return 0"
+		echo "end"
+	} >lua-probe.lua
+	cat >lua-probe-cgitrc <<EOF
+virtual-root=/
+cache-size=0
+enable-filter-overrides=1
+repo.url=lua-probe
+repo.path=$cgit_lua_probe_gitdir
+repo.commit-filter=lua:$PWD/lua-probe.lua
+EOF
+	CGIT_CONFIG="$PWD/lua-probe-cgitrc" QUERY_STRING="url=lua-probe/commit/" \
+		cgit | grep -q LUA_PROBE_YES
+}
diff --git a/tests/extensions/test-about-render.lua b/tests/extensions/test-about-render.lua
new file mode 100644
index 0000000..aa7e6ad
--- /dev/null
+++ b/tests/extensions/test-about-render.lua
@@ -0,0 +1,248 @@
+-- Unit checks for custom/extensions/about-render.lua, run under a standalone
+-- Lua by t0501-about-render.sh with the script path as the first argument.
+-- The second argument may be nolpeg, which makes the lpeg module fail to
+-- load so the escaped plain text fallback is proven even on a machine where
+-- lpeg is installed. Without it the markdown and man checks run when lpeg is
+-- present and are skipped with a note when it is not, the same way the
+-- filter itself degrades.
+
+local test_directory = arg[0]:match("^(.*)/") or "."
+local h = dofile(test_directory .. "/harness.lua")
+
+local script = arg[1]
+local mode = arg[2] or ""
+
+local has_lpeg = false
+if mode == "nolpeg" then
+	h.preload_failure("lpeg")
+else
+	has_lpeg = pcall(require, "lpeg")
+	if not has_lpeg then
+		io.write("lpeg not installed, markdown and man checks skipped\n")
+	end
+end
+
+h.load(script)
+
+local function render(filename, text)
+	return h.run({ filename }, { text })
+end
+
+-- Dispatch and the plain text rendering need nothing but the script itself,
+-- so they run whatever became of lpeg.
+
+local out, ret = render("README", "plain <text> & more")
+h.contains("no extension renders as plain text", out,
+	"<pre class='plaintext'>plain &lt;text&gt; &amp; more</pre>")
+h.equals("close answers zero", ret, 0)
+
+out = render("notes.txt", "just text")
+h.contains("an unknown extension renders as plain text", out,
+	"<pre class='plaintext'>just text</pre>")
+
+out = render(nil, "no name at all")
+h.contains("a missing filename renders as plain text", out,
+	"<pre class='plaintext'>no name at all</pre>")
+
+-- cgit's C sink stops at the first NUL byte, which the script documents, so
+-- the text past one is lost while the wrapper written separately survives.
+out = render("README", "before\0after")
+h.contains("text before a nul byte survives", out, "before")
+h.excludes("text after a nul byte is dropped", out, "after")
+h.contains("the wrapper written after the text survives", out, "</pre>")
+
+out = h.run({ "README" }, { "two ", "writes" })
+h.contains("writes are joined before rendering", out, "two writes")
+
+if mode == "nolpeg" then
+	out = render("README.md", "# Title")
+	h.contains("markdown without lpeg falls back to plain text", out,
+		"<pre class='plaintext'># Title</pre>")
+	out = render("page.1", ".SH NAME")
+	h.contains("man without lpeg falls back to plain text", out,
+		"<pre class='plaintext'>.SH NAME</pre>")
+	h.finish()
+end
+
+if not has_lpeg then
+	h.finish()
+end
+
+-- Markdown.
+
+out = render("README.md", "# Title")
+h.contains("a heading renders inside the wrapper",
+	out, "<div class='markdown'><h1>Title</h1></div>")
+
+out = render("README.md", "## Sub ##")
+h.contains("trailing hashes are stripped from a heading", out,
+	"<h2>Sub</h2>")
+
+out = render("README.MD", "# Upper")
+h.contains("the extension matches whatever its case", out, "<h1>Upper</h1>")
+
+out = render("readme.markdown", "# Long")
+h.contains("the long markdown extension dispatches too", out,
+	"<h1>Long</h1>")
+
+out = render("README.md", "line one\nline two")
+h.contains("a paragraph keeps its line break", out,
+	"<p>line one<br>line two</p>")
+
+out = render("README.md", "first para\r\nsecond line")
+h.contains("crlf line endings are normalised", out,
+	"<p>first para<br>second line</p>")
+
+out = render("README.md", "a **bold** and *leaning* word")
+h.contains("double stars embolden", out, "<strong>bold</strong>")
+h.contains("single stars lean", out, "<em>leaning</em>")
+
+out = render("README.md", "an __up__ and _down_ word")
+h.contains("double underscores embolden", out, "<strong>up</strong>")
+h.contains("single underscores lean", out, "<em>down</em>")
+
+out = render("README.md", "run `x < y` here")
+h.contains("inline code is escaped", out, "<code>x &lt; y</code>")
+
+out = render("README.md", "raw <script>alert(1)</script> here")
+h.contains("markup in text reaches the page escaped", out,
+	"&lt;script&gt;alert(1)&lt;/script&gt;")
+h.excludes("no live tag slips through", out, "<script>")
+
+out = render("README.md", "[docs](https://example.com/docs)")
+h.contains("an https link renders as an anchor", out,
+	"<a href='https://example.com/docs'>docs</a>")
+
+out = render("README.md", "[docs](docs/page.html)")
+h.contains("a relative link renders as an anchor", out,
+	"<a href='docs/page.html'>docs</a>")
+
+out = render("README.md", "[mail](mailto:a@example.com)")
+h.contains("a mailto link renders as an anchor", out,
+	"<a href='mailto:a@example.com'>mail</a>")
+
+out = render("README.md", "[bad](javascript:alert(1))")
+h.excludes("a javascript link renders no anchor", out, "<a ")
+h.contains("its text still reaches the page", out, "bad")
+
+out = render("README.md", "[bad](java\nscript:alert(1))")
+h.excludes("a split scheme is still caught", out, "<a ")
+
+out = render("README.md", "[bad](//evil.example/x)")
+h.excludes("a scheme relative link renders no anchor", out, "<a ")
+
+out = render("README.md", "[q](https://example.com/a'b)")
+h.contains("a quote in a link target is escaped", out,
+	"href='https://example.com/a&#x27;b'")
+
+out = render("README.md", "![a & b](https://example.com/i.png)")
+h.contains("an image renders with its alt text escaped", out,
+	"<img src='https://example.com/i.png' alt='a &amp; b'>")
+
+out = render("README.md", "![alt](data:image/png;base64,x)")
+h.excludes("an unsafe image renders no tag", out, "<img")
+h.contains("its alt text is kept as text", out, "![alt]")
+
+out = render("README.md", "```lua\nlocal x = 1 < 2\n```\nafter")
+h.contains("a fenced block carries its language", out,
+	"<pre><code data-lang='lua'>local x = 1 &lt; 2\n</code></pre>")
+h.contains("text after the fence renders on", out, "<p>after</p>")
+
+out = render("README.md", "~~~\n**not bold**\n~~~")
+h.contains("no inline parsing happens inside a fence", out,
+	"<code>**not bold**\n</code>")
+
+out = render("README.md", "---")
+h.contains("a rule of dashes renders a break", out, "<hr>")
+
+out = render("README.md", "- - -")
+h.contains("a spaced rule renders a break too", out, "<hr>")
+
+out = render("README.md", "> quoted words")
+h.contains("a quote renders as a blockquote", out,
+	"<blockquote><p>quoted words</p></blockquote>")
+
+out = render("README.md", "> > deep")
+h.contains("quotes nest", out,
+	"<blockquote><blockquote><p>deep</p></blockquote></blockquote>")
+
+-- A hostile readme of stacked markers has to hit the depth ceiling instead
+-- of the interpreter's stack.
+out = render("README.md", string.rep("> ", 30) .. "x")
+local _, quote_count = out:gsub("<blockquote>", "")
+h.equals("quote nesting stops at the ceiling", quote_count, 24)
+h.contains("the innermost text still renders", out, "x")
+
+out = render("README.md", string.rep("*a", 200))
+h.check("an emphasis bomb still renders something", #out > 0)
+
+out = render("README.md", "| a | b |\n| --- | --- |\n| 1 | 2 |")
+h.contains("a pipe table renders its head",
+	out, "<thead><tr><th>a</th><th>b</th></tr></thead>")
+h.contains("a pipe table renders its body",
+	out, "<tbody><tr><td>1</td><td>2</td></tr></tbody>")
+
+out = render("README.md", "a | b in prose")
+h.excludes("a pipe without a delimiter row stays prose", out, "<table")
+
+out = render("README.md", "- first\n- second")
+h.contains("dashes render an unordered list", out,
+	"<ul><li>first</li><li>second</li></ul>")
+
+out = render("README.md", "1. first\n2. second")
+h.contains("numbers render an ordered list", out,
+	"<ol><li>first</li><li>second</li></ol>")
+
+out = render("README.md", "- plain\n1. numbered")
+h.contains("a change of marker splits the list", out, "</ul><ol>")
+
+out = render("README.md", "- a **bold** item")
+h.contains("list items parse their text", out,
+	"<li>a <strong>bold</strong> item</li>")
+
+out = render("README.md", string.rep("a", 512 * 1024 + 1))
+h.contains("an oversized readme renders as plain text", out,
+	"<pre class='plaintext'>")
+
+-- Man pages.
+
+out = render("page.1", ".SH NAME")
+h.contains("a section heading renders", out,
+	"<div class='markdown manpage'><h2>NAME</h2></div>")
+
+out = render("page.man", '.SH "TWO WORDS"')
+h.contains("a quoted heading argument is unquoted", out,
+	"<h2>TWO WORDS</h2>")
+
+out = render("page.3", ".SS Details")
+h.contains("a subsection renders one level down", out, "<h3>Details</h3>")
+
+out = render("page.1", ".B bold words\nplain after")
+h.contains("the bold macro renders strong", out,
+	"<p><strong>bold words</strong><br>plain after</p>")
+
+out = render("page.1", "a \\fBbold\\fR c")
+h.contains("font escapes carry across a run", out,
+	"<p>a <strong>bold</strong> c</p>")
+
+out = render("page.1", "x \\(em y \\- z")
+h.contains("character escapes are translated", out, "<p>x - y - z</p>")
+
+out = render("page.1", ".nf\ncode <x>\n.fi\nafter")
+h.contains("a no fill block renders as code", out,
+	"<pre><code>code &lt;x&gt;\n</code></pre>")
+h.contains("filling resumes after it", out, "<p>after</p>")
+
+out = render("page.1", '.\\" a comment\nvisible')
+h.excludes("a roff comment is dropped", out, "comment")
+h.contains("the line after it renders", out, "visible")
+
+out = render("page.1", "first\n\nsecond")
+h.contains("a blank line splits paragraphs", out,
+	"<p>first</p><p>second</p>")
+
+out = render("page.1", ".TH title 1\nbody")
+h.excludes("the title macro renders nothing itself", out, "title 1")
+h.contains("the body after it renders", out, "<p>body</p>")
+
+h.finish()
diff --git a/tests/extensions/test-auth.lua b/tests/extensions/test-auth.lua
new file mode 100644
index 0000000..359f52e
--- /dev/null
+++ b/tests/extensions/test-auth.lua
@@ -0,0 +1,302 @@
+-- Unit checks for the two auth filters, run under a standalone Lua by
+-- t0505-auth.sh with the script path as the first argument and the variant,
+-- inline or file, as the second. The scripts take luaossl and luaposix at
+-- load, so the harness meets both with deterministic stand-ins, which keeps
+-- every check about this script's own logic, the cookie layout, the expiry
+-- and field rules, the redirect vetting and the action flows, rather than
+-- about OpenSSL. The signing secret is pinned by replacing get_secret, and
+-- the account and access lookups are populated through each variant's own
+-- channel, the documented account_hash and repo_userset swap points for the
+-- inline script and fixture files reached through a redirected io.open for
+-- the file one. Both variants carry the same data so the flow checks read
+-- identically for the two.
+
+local test_directory = arg[0]:match("^(.*)/") or "."
+local h = dofile(test_directory .. "/harness.lua")
+
+local script = arg[1]
+local variant = arg[2]
+
+h.stub_auth_modules()
+
+-- The password behind every test account, stored as what the harness crypt
+-- stand-in returns for it so a login with it verifies and any other fails.
+local password = "open sesame"
+local stored_hash = "$6$rounds=300000$testsalt$" .. password
+
+if variant == "file" then
+	local users_file = io.open("auth-users", "w")
+	users_file:write("Alice:" .. stored_hash .. "\r\n")
+	users_file:write("not a parsable line\n")
+	users_file:close()
+	local groups_file = io.open("auth-groups", "w")
+	groups_file:write("devs:Alice, bob\n")
+	groups_file:write("others:carol\n")
+	groups_file:close()
+	local repos_file = io.open("auth-repos", "w")
+	repos_file:write("secret-repo:devs\n")
+	repos_file:write("empty-repo:ghosts\n")
+	repos_file:close()
+	h.redirect_file("/etc/cgit-auth/users", "auth-users")
+	h.redirect_file("/etc/cgit-auth/groups", "auth-groups")
+	h.redirect_file("/etc/cgit-auth/repos", "auth-repos")
+end
+
+h.load(script)
+
+function get_secret()
+	return string.rep("0123456789abcdef", 4)
+end
+
+if variant == "inline" then
+	local accounts = { alice = stored_hash }
+	local access = {
+		["secret-repo"] = { alice = true, bob = true },
+		["empty-repo"] = {},
+	}
+	function account_hash(user)
+		if user == nil then
+			return nil
+		end
+		return accounts[user:lower()]
+	end
+	function repo_userset(repo)
+		if repo == nil then
+			return nil
+		end
+		return access[repo]
+	end
+end
+
+-- The lookups themselves, which are the part the two variants do not share.
+
+local hash = account_hash("ALICE")
+h.equals("an account is found whatever its case", hash, stored_hash)
+h.equals("an unknown account is not", account_hash("nobody"), nil)
+h.equals("a nil user is not", account_hash(nil), nil)
+
+local userset = repo_userset("secret-repo")
+h.check("a protected repository lists its users",
+	userset ~= nil and userset.alice and userset.bob)
+h.equals("an unlisted repository is public", repo_userset("unlisted"), nil)
+h.equals("the repository name matches case exactly",
+	repo_userset("Secret-Repo"), nil)
+local empty = repo_userset("empty-repo")
+h.check("a protected repository with no members denies as an empty set",
+	empty ~= nil and next(empty) == nil)
+
+if variant == "file" then
+	h.redirect_file("/etc/cgit-auth/users", "auth-users-missing")
+	h.equals("a missing users file turns every login down",
+		account_hash("alice"), nil)
+	h.redirect_file("/etc/cgit-auth/users", "auth-users")
+end
+
+-- The url and cookie helpers.
+
+h.equals("decode handles escapes and plus", url_decode("%41+b"), "A b")
+h.equals("encode escapes what is not a word", url_encode("a b|c"), "a+b%7Cc")
+local tricky = "x&=?|"
+h.equals("decode inverts encode", url_decode(url_encode(tricky)), tricky)
+
+local params = parse_query("u=a&p=b=c&x=%41")
+h.equals("a query splits on ampersands", params.u, "a")
+h.equals("a value keeps its own equals signs", params.p, "b=c")
+h.equals("a value is decoded", params.x, "A")
+
+h.equals("a cookie is found among others",
+	get_cookie("foo=1; cgitauth=abc; bar=2", "cgitauth"), "abc")
+h.equals("a lone cookie is found", get_cookie("cgitauth=abc", "cgitauth"),
+	"abc")
+h.equals("no header yields no cookie", get_cookie(nil, "cgitauth"), nil)
+h.equals("a longer name does not match",
+	get_cookie("xcgitauth=z", "cgitauth"), nil)
+h.equals("a magic character in the name is taken literally",
+	get_cookie("a-b=z", "a-b"), "z")
+
+h.check("equal strings compare equal", constant_equals("abc", "abc"))
+h.check("differing strings do not", not constant_equals("abc", "abd"))
+h.check("differing lengths do not", not constant_equals("a", "ab"))
+h.check("non strings do not", not constant_equals(nil, "a"))
+
+h.check("a local path is a safe redirect", is_safe_redirect("/x"))
+h.check("a scheme relative target is not", not is_safe_redirect("//evil"))
+h.check("a backslash variant is not", not is_safe_redirect("/\\evil"))
+h.check("a missing target is not", not is_safe_redirect(nil))
+
+h.equals("control characters are stripped from header values",
+	strip_controls("a\r\nb"), "ab")
+
+-- Signing and verification.
+
+local now = os.time()
+
+local cookie = secure_value("username", "alice", now + 3600)
+h.equals("a signed value verifies and comes back",
+	validate_value("username", cookie), "alice")
+
+cookie = secure_value("username", "a|b", now + 3600)
+h.equals("a value holding the separator survives the round trip",
+	validate_value("username", cookie), "a|b")
+
+cookie = secure_value("username", "a\nb", now + 3600)
+h.equals("a signed control character is still rejected on the way out",
+	validate_value("username", cookie), nil)
+
+cookie = secure_value("redirect", "/repo/?a=b", 0)
+h.equals("an expiration of zero never expires",
+	validate_value("redirect", cookie), "/repo/?a=b")
+
+cookie = secure_value("username", "alice", now - 10)
+h.equals("an expired value is rejected",
+	validate_value("username", cookie), nil)
+
+cookie = secure_value("username", "alice", now + 3600)
+local flipped = cookie:sub(1, -2) ..
+	(cookie:sub(-1) == "0" and "1" or "0")
+h.equals("a tampered signature is rejected",
+	validate_value("username", flipped), nil)
+
+h.equals("a value signed for one field does not serve another",
+	validate_value("redirect", cookie), nil)
+
+h.equals("no cookie does not verify", validate_value("username", nil), nil)
+h.equals("a tiny cookie does not verify", validate_value("username", "ab"),
+	nil)
+h.equals("a leading separator does not verify",
+	validate_value("username", "|x|1|s|sig"), nil)
+h.equals("an unsigned cookie does not verify",
+	validate_value("username", "username|alice|123|salt"), nil)
+h.equals("an exponent spelling of the expiry does not verify",
+	validate_value("username", "username|alice|1e9|salt|beef"), nil)
+h.equals("an empty value signs to nothing", secure_value("username", "", 1),
+	"")
+
+-- The headers the filter writes itself.
+
+h.reset()
+set_cookie("cgitauth", "value")
+local out = h.output()
+h.contains("a session cookie carries the hardening attributes", out,
+	"Set-Cookie: cgitauth=value; HttpOnly; SameSite=Lax; Path=/; Secure; " ..
+	"Max-Age=604800\n")
+
+h.reset()
+set_cookie("cgitauth", "")
+h.contains("an empty value clears the cookie instead", h.output(),
+	"Set-Cookie: cgitauth=; HttpOnly; SameSite=Lax; Path=/; Secure; " ..
+	"Max-Age=0\n")
+
+h.reset()
+redirect_to("/x\r\nX-Evil: 1")
+out = h.output()
+h.contains("a newline cannot split the location header", out,
+	"Location: /xX-Evil: 1\n")
+h.excludes("no carriage return slips through", out, "\r")
+
+-- The three actions, driven the way cgit drives them, an open carrying the
+-- request, a write only for the posted form and the answer read off the
+-- close.
+
+local function run_action(action, opts)
+	opts = opts or {}
+	h.reset()
+	filter_open(action, opts.cookie or "", opts.method or "GET", "", "",
+		"/", "example.org", "on", opts.repo or "", "summary",
+		opts.url or "/repo/", "/?p=login")
+	if opts.body then
+		filter_write(opts.body)
+	end
+	local ret = filter_close()
+	return h.output(), ret
+end
+
+local ret
+
+out, ret = run_action("authenticate-cookie", { repo = "unlisted" })
+h.equals("a public repository needs no cookie", ret, 1)
+
+out, ret = run_action("authenticate-cookie", { repo = "secret-repo" })
+h.equals("a protected repository turns a bare request away", ret, 0)
+
+local session = secure_value("username", "Alice", now + 3600)
+out, ret = run_action("authenticate-cookie",
+	{ repo = "secret-repo", cookie = "cgitauth=" .. session })
+h.equals("a signed session for a member is let through", ret, 1)
+
+out, ret = run_action("authenticate-cookie",
+	{ repo = "empty-repo", cookie = "cgitauth=" .. session })
+h.equals("a memberless repository denies even a valid session", ret, 0)
+
+local outsider = secure_value("username", "carol", now + 3600)
+out, ret = run_action("authenticate-cookie",
+	{ repo = "secret-repo", cookie = "cgitauth=" .. outsider })
+h.equals("a signed session for an outsider is turned away", ret, 0)
+
+local forged = session:sub(1, -2) ..
+	(session:sub(-1) == "0" and "1" or "0")
+out, ret = run_action("authenticate-cookie",
+	{ repo = "secret-repo", cookie = "cgitauth=" .. forged })
+h.equals("a forged session is turned away", ret, 0)
+
+out, ret = run_action("no-such-action", {})
+h.equals("an unknown action denies rather than raising", ret, 0)
+
+out, ret = run_action("body", { url = "/repo/log/?q=x" })
+h.contains("the login form posts to the login url", out,
+	"<form method='post' action='/?p=login'>")
+local token = out:match("name='redirect' value='([^']*)'")
+h.equals("the form carries a signed way back",
+	token and validate_value("redirect", token), "/repo/log/?q=x")
+
+out, ret = run_action("body", { url = "//evil.example/x" })
+token = out:match("name='redirect' value='([^']*)'")
+h.equals("an unsafe destination is swapped for the login page",
+	token and validate_value("redirect", token), "/?p=login")
+
+local way_back = secure_value("redirect", "/repo/", 0)
+
+out, ret = run_action("authenticate-post", {
+	method = "POST",
+	body = "username=Alice&password=" .. url_encode(password) ..
+		"&redirect=" .. url_encode(way_back),
+})
+h.contains("a good login redirects back", out, "Status: 302")
+h.contains("to where the form said", out, "Location: /repo/\n")
+local granted = out:match("Set%-Cookie: cgitauth=([^;]*);")
+h.equals("and grants a session that verifies",
+	granted and validate_value("username", granted), "Alice")
+
+out, ret = run_action("authenticate-post", {
+	method = "POST",
+	body = "username=Alice&password=wrong&redirect=" ..
+		url_encode(way_back),
+})
+h.contains("a bad password redirects the same way", out, "Status: 302")
+h.contains("but clears the session cookie", out,
+	"Set-Cookie: cgitauth=; ")
+
+out, ret = run_action("authenticate-post", {
+	method = "POST",
+	body = "username=nobody&password=x&redirect=" .. url_encode(way_back),
+})
+h.contains("an unknown user is told nothing different", out,
+	"Set-Cookie: cgitauth=; ")
+
+out, ret = run_action("authenticate-post", {
+	method = "POST",
+	body = "username=Alice&password=" .. url_encode(password),
+})
+h.contains("a post without the signed token is not served", out,
+	"Status: 404")
+
+local hijack = secure_value("redirect", "//evil.example/", 0)
+out, ret = run_action("authenticate-post", {
+	method = "POST",
+	body = "username=Alice&password=" .. url_encode(password) ..
+		"&redirect=" .. url_encode(hijack),
+})
+h.contains("even a signed unsafe destination is not followed", out,
+	"Status: 404")
+
+h.finish()
diff --git a/tests/extensions/test-email-avatar.lua b/tests/extensions/test-email-avatar.lua
new file mode 100644
index 0000000..d6bd957
--- /dev/null
+++ b/tests/extensions/test-email-avatar.lua
@@ -0,0 +1,77 @@
+-- Unit checks for the two avatar email filters, run under a standalone Lua
+-- by t0504-email-avatar.sh with the script path as the first argument. The
+-- two scripts differ only in the service they point at, so the expected host
+-- is picked from the script's name. The second argument chooses how the
+-- openssl.digest dependency is met, stub swaps in the deterministic fake
+-- from the harness, and real uses an installed luaossl and adds the one
+-- check only a genuine MD5 can pass.
+
+local test_directory = arg[0]:match("^(.*)/") or "."
+local h = dofile(test_directory .. "/harness.lua")
+
+local script = arg[1]
+local mode = arg[2] or "stub"
+
+local base_url = "https://www.gravatar.com/avatar/"
+local alt_text = "Gravatar"
+if script:find("libravatar", 1, true) then
+	base_url = "https://seccdn.libravatar.org/avatar/"
+	alt_text = "Libravatar"
+end
+
+if mode == "stub" then
+	h.stub_digest()
+end
+
+h.load(script)
+
+local function render(email, name)
+	return h.run({ email, "commit" }, { name })
+end
+
+local function hash_of(output)
+	local prefix = base_url:gsub("([%^%$%(%)%%%.%[%]%*%+%-%?])", "%%%1")
+	return output:match("src='" .. prefix .. "(%x+)%?")
+end
+
+local out, ret = render("<author@example.com>", "A U Thor")
+h.contains("an icon is drawn for an address", out, "<img src='" .. base_url)
+h.contains("the size lands in the query", out, "?s=13&amp;d=retro'")
+h.contains("the alt text names the service", out, "alt='" .. alt_text .. "'")
+h.contains("width matches the size", out, "width='13'")
+h.contains("height matches the size", out, "height='13'")
+h.contains("the fetch is deferred", out, "loading='lazy' decoding='async'")
+h.contains("the name follows the icon", out, "> A U Thor")
+h.equals("close answers zero", ret, 0)
+h.check("the hash is hex", hash_of(out) ~= nil)
+
+-- The service hashes the trimmed lowercase address, so every spelling of one
+-- address has to reach it as the same hash.
+local plain = hash_of(render("author@example.com", "x"))
+local wrapped = hash_of(render("<author@example.com>", "x"))
+local shouting = hash_of(render("  <AUTHOR@Example.COM>  ", "x"))
+h.check("angle brackets do not change the hash", plain == wrapped)
+h.check("case and padding do not change the hash", plain == shouting)
+
+local other = hash_of(render("other@example.com", "x"))
+h.check("a different address hashes differently", plain ~= other)
+
+out = render(nil, "A U Thor")
+h.equals("no address draws no icon", out, "A U Thor")
+
+out = render("", "A U Thor")
+h.equals("an empty address draws no icon", out, "A U Thor")
+
+out = render("<>", "A U Thor")
+h.equals("empty angle brackets draw no icon", out, "A U Thor")
+
+out = h.run({ "<author@example.com>", "commit" }, { "A U ", "Thor" })
+h.contains("the name is buffered across writes", out, "> A U Thor")
+
+if mode == "real" then
+	out = render("test@example.com", "x")
+	h.equals("a known address hashes to its published md5",
+		hash_of(out), "55502f40dc8b7c769880b10874abc9d0")
+end
+
+h.finish()
diff --git a/tests/extensions/test-link-commits.lua b/tests/extensions/test-link-commits.lua
new file mode 100644
index 0000000..6c6d28d
--- /dev/null
+++ b/tests/extensions/test-link-commits.lua
@@ -0,0 +1,77 @@
+-- Unit checks for custom/extensions/link-commits.lua, run under a standalone
+-- Lua by t0503-link-commits.sh with the script path as the argument. The
+-- shipped configuration links bare object names to ./?id= and issue marks
+-- like #123 to bugs.example.com, and everything here checks that shape, the
+-- length bounds and frontier on hash recognition, and the rule that no run
+-- of text is ever wrapped twice.
+
+local test_directory = arg[0]:match("^(.*)/") or "."
+local h = dofile(test_directory .. "/harness.lua")
+
+h.load(arg[1])
+
+local function render(text)
+	return h.run({}, { text })
+end
+
+local out, ret = render("see #123 for details")
+h.contains("issue mark becomes a link", out,
+	"<a href='https://bugs.example.com/?bug=123'>#123</a>")
+h.contains("text around the link survives", out, "see ")
+h.contains("text after the link survives", out, " for details")
+h.equals("close answers zero", ret, 0)
+
+out = render("fixed in deadbee")
+h.contains("seven hex characters link", out,
+	"<a href='./?id=deadbee'>deadbee</a>")
+
+out = render("fixed in deadbe")
+h.excludes("six hex characters stay text", out, "<a")
+
+out = render("fixed in 1234567")
+h.contains("an all digit run still links", out,
+	"<a href='./?id=1234567'>1234567</a>")
+
+local sha1 = string.rep("0123456789abcdef", 2) .. "01234567"
+out = render("commit " .. sha1)
+h.contains("a full sha1 name links", out, "'./?id=" .. sha1 .. "'")
+
+local sha256 = string.rep("0123456789abcdef", 4)
+out = render("commit " .. sha256)
+h.contains("a full sha256 name links", out, "'./?id=" .. sha256 .. "'")
+
+out = render("commit " .. sha256 .. "0")
+h.excludes("sixty five hex characters stay text", out, "<a")
+
+out = render("prefixdeadbeef")
+h.excludes("a hex run inside a word stays text", out, "<a")
+
+out = render("deadbeefy")
+h.excludes("a hex run ending inside a word stays text", out, "<a")
+
+-- The issue rule wins the overlap because it starts first, and the digit run
+-- inside it must not be wrapped a second time.
+out = render("see #1234567 for details")
+h.contains("the issue rule wins an overlap", out,
+	"<a href='https://bugs.example.com/?bug=1234567'>#1234567</a>")
+h.excludes("the overlapped hash is dropped", out, "./?id=")
+
+out = render("#12 and cafebabe12")
+h.contains("both rules fire on one message", out, "?bug=12'>#12</a>")
+h.contains("the object link also fires", out,
+	"<a href='./?id=cafebabe12'>cafebabe12</a>")
+
+-- One request is delivered as several writes, and a match split across two of
+-- them has to be seen whole.
+out = h.run({}, { "see #45", "6 and be done" })
+h.contains("a match split across writes still links", out,
+	"?bug=456'>#456</a>")
+
+out, ret = render("")
+h.equals("an empty message stays empty", out, "")
+h.equals("an empty message still answers zero", ret, 0)
+
+out = render("plain words only")
+h.equals("a message with no matches passes through", out, "plain words only")
+
+h.finish()
diff --git a/tests/extensions/test-syntax-highlight.lua b/tests/extensions/test-syntax-highlight.lua
new file mode 100644
index 0000000..3b0eeb8
--- /dev/null
+++ b/tests/extensions/test-syntax-highlight.lua
@@ -0,0 +1,94 @@
+-- Unit checks for custom/extensions/syntax-highlight.lua, run under a
+-- standalone Lua by t0502-syntax-highlight.sh with the script path as the
+-- first argument. The filter remembers whether the lexers loaded for the
+-- life of the interpreter, so the two sides of that split are two runs of
+-- this file. In highlight mode the shell points CGIT_SCINTILLUA_PATH at the
+-- fake-lexers directory beside this file and every path through a working
+-- lexer is checked, and in nolexers mode it points at an empty directory so
+-- the escaped fallback is what everything renders through.
+
+local test_directory = arg[0]:match("^(.*)/") or "."
+local h = dofile(test_directory .. "/harness.lua")
+
+local script = arg[1]
+local mode = arg[2] or "highlight"
+
+h.load(script)
+
+local function render(filename, text)
+	return h.run({ filename }, { text })
+end
+
+if mode == "nolexers" then
+	local out, ret = render("hello.fake", "if 42")
+	h.equals("without lexers source is served escaped", out, "if 42")
+	h.equals("close answers zero", ret, 0)
+
+	out = render("hello.fake", "a <b> & c")
+	h.equals("the fallback escapes markup", out, "a &lt;b&gt; &amp; c")
+
+	-- Large output leaves in slices, and a byte lost at a boundary would
+	-- put the line numbers beside it out of step, so the whole escaped
+	-- blob has to come back intact across several slices.
+	out = render("big.fake", string.rep("x<y>", 30000))
+	h.equals("slicing loses nothing at the boundaries", out,
+		string.rep("x&lt;y&gt;", 30000))
+
+	h.finish()
+end
+
+local out, ret = render("hello.fake", "if 42 'hi' & zz")
+h.contains("keywords are wrapped in their class", out,
+	"<span class='hl-keyword'>if</span>")
+h.contains("numbers are wrapped in their class", out,
+	"<span class='hl-number'>42</span>")
+h.contains("a dotted tag maps by its first component", out,
+	"<span class='hl-string'>'hi'</span>")
+h.contains("bytes between tokens are escaped", out, " &amp; ")
+h.contains("later tokens still highlight", out,
+	"<span class='hl-keyword'>zz</span>")
+h.equals("close answers zero", ret, 0)
+
+out = h.run({ "split.fake" }, { "i", "f" })
+h.equals("writes are joined before lexing", out,
+	"<span class='hl-keyword'>if</span>")
+
+-- The short lexer tags four bytes and stops, and every byte after it still
+-- has to reach the page.
+out = render("cut.short", "abcd<ef>")
+h.equals("a lexer stopping early leaves an escaped tail", out,
+	"<span class='hl-keyword'>abcd</span>&lt;ef&gt;")
+
+out = render("boom.badlex", "some <code>")
+h.equals("a lexer that raises falls back to escaped text", out,
+	"some &lt;code&gt;")
+
+-- The viadetect lexer name only resolves through detect(), so highlighted
+-- output proves the detection path ran ahead of the extension path.
+out = render("script.viadetect", "if")
+h.equals("filename detection picks the lexer", out,
+	"<span class='hl-keyword'>if</span>")
+
+out = render("tool.py", "import <x>")
+h.equals("an extension with no lexer serves escaped text", out,
+	"import &lt;x&gt;")
+
+out = render("noextension", "words <here>")
+h.equals("a file with no extension serves escaped text", out,
+	"words &lt;here&gt;")
+
+out = render("big.fake", string.rep("a", 512 * 1024 + 1))
+h.excludes("an oversized blob skips the lexing pass", out, "<span")
+h.equals("and still arrives whole", #out, 512 * 1024 + 1)
+
+out, ret = render("empty.fake", "")
+h.equals("an empty blob renders empty", out, "")
+h.equals("an empty blob still answers zero", ret, 0)
+
+-- cgit's C sink stops at the first NUL byte, which the script documents for
+-- binaries that slip past the text detection.
+out = render("blob.bin", "ab\0cd")
+h.contains("bytes before a nul survive", out, "ab")
+h.excludes("bytes after a nul are dropped", out, "cd")
+
+h.finish()
diff --git a/tests/t0501-about-render.sh b/tests/t0501-about-render.sh
new file mode 100755
index 0000000..eff2a61
--- /dev/null
+++ b/tests/t0501-about-render.sh
@@ -0,0 +1,90 @@
+#!/bin/sh
+
+# Checks about-render.lua, the shipped about-filter. The unit checks drive
+# the script under every suitable standalone Lua through the harness in
+# extensions/, once as installed and once with lpeg forced away so the
+# plain text fallback is proven everywhere. A repository with a markdown
+# readme is then rendered through cgit itself, where the outcome depends on
+# whether the Lua inside the binary has lpeg, so a probe decides which of
+# the two right answers to expect.
+
+test_description='Check the shipped about-render extension'
+CGIT_TEST_NO_CREATE_REPOS=YesPlease
+. ./setup.sh
+. "$TEST_OUTPUT_DIRECTORY/extensions/lib.sh"
+
+interpreters=$(ext_lua_interpreters 4)
+test -z "$interpreters" &&
+	say 'no standalone lua on the path, unit checks skipped'
+
+for lua in $interpreters
+do
+	test_expect_success "unit checks under $lua" "
+		'$lua' '$EXT_TEST_DIRECTORY/test-about-render.lua' \
+			'$EXTENSIONS_DIRECTORY/about-render.lua'
+	"
+
+	test_expect_success "fallback checks without lpeg under $lua" "
+		'$lua' '$EXT_TEST_DIRECTORY/test-about-render.lua' \
+			'$EXTENSIONS_DIRECTORY/about-render.lua' nolpeg
+	"
+done
+
+test_expect_success 'create a repository with a markdown readme' '
+	test_create_repo repos/md &&
+	(
+		cd repos/md &&
+		cat >README.md <<-\EOF &&
+		# The Title
+
+		A **bold** claim and a <script>alert(1)</script> attempt.
+		EOF
+		git add README.md &&
+		git commit -m "add readme"
+	)
+'
+
+test_expect_success 'point cgit at it through the about filter' '
+	cat >cgitrc <<-EOF
+	virtual-root=/
+	cache-size=0
+	enable-filter-overrides=1
+	repo.url=md
+	repo.path=$PWD/repos/md/.git
+	repo.readme=master:README.md
+	repo.about-filter=lua:$EXTENSIONS_DIRECTORY/about-render.lua
+	EOF
+'
+
+if test "$CGIT_HAS_LUA" -eq 1
+then
+	if cgit_lua_probe "$PWD/repos/md/.git" lpeg
+	then
+		test_set_prereq CGIT_LUA_LPEG
+	else
+		test_set_prereq CGIT_LUA_NOLPEG
+		say 'cgit lua has no lpeg, expecting the plain text fallback'
+	fi
+else
+	say 'cgit built without lua, filter checks through cgit skipped'
+fi
+
+test_expect_success CGIT_LUA_LPEG 'the about page renders the markdown' '
+	cgit_url "md/about/" >tmp &&
+	grep "<h1>The Title</h1>" tmp &&
+	grep "<strong>bold</strong>" tmp
+'
+
+test_expect_success CGIT_LUA_LPEG 'readme markup reaches the page escaped' '
+	cgit_url "md/about/" >tmp &&
+	grep "&lt;script&gt;alert(1)&lt;/script&gt;" tmp &&
+	! grep "<script>alert(1)" tmp
+'
+
+test_expect_success CGIT_LUA_NOLPEG 'without lpeg the readme is served escaped' '
+	cgit_url "md/about/" >tmp &&
+	grep "<pre class=.plaintext.>" tmp &&
+	grep "# The Title" tmp
+'
+
+test_done
diff --git a/tests/t0502-syntax-highlight.sh b/tests/t0502-syntax-highlight.sh
new file mode 100755
index 0000000..c7cbf89
--- /dev/null
+++ b/tests/t0502-syntax-highlight.sh
@@ -0,0 +1,74 @@
+#!/bin/sh
+
+# Checks syntax-highlight.lua, the shipped source-filter. The real
+# Scintillua collection is not assumed anywhere, because the fake lexer
+# module under extensions/fake-lexers drives every path through the
+# filter deterministically. The unit checks run twice per interpreter, once
+# with the fake lexers found and once with an empty directory so the escaped
+# fallback is what everything renders through. The run through cgit itself
+# places the fake lexers beside the config file, which is the probe the
+# filter documents for a scintillua directory next to cgitrc.
+
+test_description='Check the shipped syntax-highlight extension'
+CGIT_TEST_NO_CREATE_REPOS=YesPlease
+. ./setup.sh
+. "$TEST_OUTPUT_DIRECTORY/extensions/lib.sh"
+
+interpreters=$(ext_lua_interpreters 5)
+test -z "$interpreters" &&
+	say 'no standalone lua on the path, unit checks skipped'
+
+for lua in $interpreters
+do
+	test_expect_success "highlighting checks under $lua" "
+		CGIT_SCINTILLUA_PATH='$EXT_TEST_DIRECTORY/fake-lexers' \
+		'$lua' '$EXT_TEST_DIRECTORY/test-syntax-highlight.lua' \
+			'$EXTENSIONS_DIRECTORY/syntax-highlight.lua' highlight
+	"
+
+	test_expect_success "fallback checks without lexers under $lua" "
+		mkdir -p empty-lexers &&
+		CGIT_SCINTILLUA_PATH=\"\$PWD/empty-lexers\" \
+		'$lua' '$EXT_TEST_DIRECTORY/test-syntax-highlight.lua' \
+			'$EXTENSIONS_DIRECTORY/syntax-highlight.lua' nolexers
+	"
+done
+
+test "$CGIT_HAS_LUA" -eq 1 && test_set_prereq CGIT_LUA
+test "$CGIT_HAS_LUA" -eq 1 ||
+	say 'cgit built without lua, filter checks through cgit skipped'
+
+test_expect_success 'create a repository holding a lexable file' '
+	test_create_repo repos/fake &&
+	(
+		cd repos/fake &&
+		echo "if 42 & zz" >hello.fake &&
+		git add hello.fake &&
+		git commit -m "add hello"
+	)
+'
+
+test_expect_success 'place the fake lexers beside a config naming the filter' '
+	mkdir -p scintillua &&
+	cp -R "$EXT_TEST_DIRECTORY/fake-lexers" scintillua/lexers &&
+	cat >cgitrc <<-EOF
+	virtual-root=/
+	cache-size=0
+	enable-filter-overrides=1
+	repo.url=fake
+	repo.path=$PWD/repos/fake/.git
+	repo.source-filter=lua:$EXTENSIONS_DIRECTORY/syntax-highlight.lua
+	EOF
+'
+
+test_expect_success CGIT_LUA 'the tree view is highlighted' '
+	cgit_url "fake/tree/hello.fake" >tmp &&
+	grep "<span class=.hl-keyword.>if</span>" tmp &&
+	grep "<span class=.hl-number.>42</span>" tmp
+'
+
+test_expect_success CGIT_LUA 'bytes between tokens reach the page escaped' '
+	grep "<span class=.hl-number.>42</span> &amp; " tmp
+'
+
+test_done
diff --git a/tests/t0503-link-commits.sh b/tests/t0503-link-commits.sh
new file mode 100755
index 0000000..11b1b54
--- /dev/null
+++ b/tests/t0503-link-commits.sh
@@ -0,0 +1,60 @@
+#!/bin/sh
+
+# Checks link-commits.lua, the shipped commit-filter, whose configuration as
+# shipped links bare object names to ./?id= and issue marks like #123 to
+# bugs.example.com. The unit checks cover the matching rules under every
+# suitable standalone Lua, and a commit whose message carries one of each is
+# then rendered through cgit itself.
+
+test_description='Check the shipped link-commits extension'
+CGIT_TEST_NO_CREATE_REPOS=YesPlease
+. ./setup.sh
+. "$TEST_OUTPUT_DIRECTORY/extensions/lib.sh"
+
+interpreters=$(ext_lua_interpreters 4)
+test -z "$interpreters" &&
+	say 'no standalone lua on the path, unit checks skipped'
+
+for lua in $interpreters
+do
+	test_expect_success "unit checks under $lua" "
+		'$lua' '$EXT_TEST_DIRECTORY/test-link-commits.lua' \
+			'$EXTENSIONS_DIRECTORY/link-commits.lua'
+	"
+done
+
+test "$CGIT_HAS_LUA" -eq 1 && test_set_prereq CGIT_LUA
+test "$CGIT_HAS_LUA" -eq 1 ||
+	say 'cgit built without lua, filter checks through cgit skipped'
+
+test_expect_success 'create a repository whose commit message holds matches' '
+	test_create_repo repos/linky &&
+	(
+		cd repos/linky &&
+		echo content >file &&
+		git add file &&
+		git commit -m "fix #123 near deadbeefcafe1234"
+	)
+'
+
+test_expect_success 'point cgit at it through the commit filter' '
+	cat >cgitrc <<-EOF
+	virtual-root=/
+	cache-size=0
+	enable-filter-overrides=1
+	repo.url=linky
+	repo.path=$PWD/repos/linky/.git
+	repo.commit-filter=lua:$EXTENSIONS_DIRECTORY/link-commits.lua
+	EOF
+'
+
+test_expect_success CGIT_LUA 'the issue mark links out on the commit page' '
+	cgit_url "linky/commit/" >tmp &&
+	grep "bugs.example.com/?bug=123.>#123</a>" tmp
+'
+
+test_expect_success CGIT_LUA 'the object name links to its own page' '
+	grep "id=deadbeefcafe1234.>deadbeefcafe1234</a>" tmp
+'
+
+test_done
diff --git a/tests/t0504-email-avatar.sh b/tests/t0504-email-avatar.sh
new file mode 100755
index 0000000..0a4b74f
--- /dev/null
+++ b/tests/t0504-email-avatar.sh
@@ -0,0 +1,77 @@
+#!/bin/sh
+
+# Checks email-gravatar.lua and email-libravatar.lua, the shipped email
+# filters, which differ only in the service the icon is fetched from. The
+# unit checks run each under every suitable standalone Lua with a
+# deterministic digest standing in for luaossl, and once more against the
+# real module wherever it is installed, which adds the check that a known
+# address hashes to its published md5. The run through cgit itself needs
+# luaossl inside the binary's own Lua, so it is probed for rather than
+# assumed.
+
+test_description='Check the shipped email avatar extensions'
+CGIT_TEST_NO_CREATE_REPOS=YesPlease
+. ./setup.sh
+. "$TEST_OUTPUT_DIRECTORY/extensions/lib.sh"
+
+interpreters=$(ext_lua_interpreters 4)
+test -z "$interpreters" &&
+	say 'no standalone lua on the path, unit checks skipped'
+
+for lua in $interpreters
+do
+	for script in email-gravatar email-libravatar
+	do
+		test_expect_success "$script checks under $lua" "
+			'$lua' '$EXT_TEST_DIRECTORY/test-email-avatar.lua' \
+				'$EXTENSIONS_DIRECTORY/$script.lua' stub
+		"
+
+		if "$lua" -e "require([[openssl.digest]])" >/dev/null 2>&1
+		then
+			test_expect_success "$script checks with real luaossl under $lua" "
+				'$lua' '$EXT_TEST_DIRECTORY/test-email-avatar.lua' \
+					'$EXTENSIONS_DIRECTORY/$script.lua' real
+			"
+		fi
+	done
+done
+
+test_expect_success 'create a repository with one commit' '
+	test_create_repo repos/avatar &&
+	(
+		cd repos/avatar &&
+		echo content >file &&
+		git add file &&
+		git commit -m "add file"
+	)
+'
+
+if test "$CGIT_HAS_LUA" -eq 1 &&
+	cgit_lua_probe "$PWD/repos/avatar/.git" openssl.digest
+then
+	test_set_prereq CGIT_LUA_OSSL
+else
+	say 'cgit lua has no luaossl, filter checks through cgit skipped'
+fi
+
+test_expect_success CGIT_LUA_OSSL 'point cgit at it through the email filter' '
+	cat >cgitrc <<-EOF
+	virtual-root=/
+	cache-size=0
+	enable-filter-overrides=1
+	repo.url=avatar
+	repo.path=$PWD/repos/avatar/.git
+	repo.email-filter=lua:$EXTENSIONS_DIRECTORY/email-gravatar.lua
+	EOF
+'
+
+# The address behind the hash is author@example.com, the identity the test
+# library commits under.
+test_expect_success CGIT_LUA_OSSL 'the commit page draws the author icon' '
+	cgit_url "avatar/commit/" >tmp &&
+	grep "www.gravatar.com/avatar/5c1e6d6e64e12aca17657581a48005d1" tmp &&
+	grep "loading=.lazy." tmp
+'
+
+test_done
diff --git a/tests/t0505-auth.sh b/tests/t0505-auth.sh
new file mode 100755
index 0000000..d4dcd52
--- /dev/null
+++ b/tests/t0505-auth.sh
@@ -0,0 +1,68 @@
+#!/bin/sh
+
+# Checks auth-file.lua and auth-inline.lua, the shipped auth filters, which
+# share their cookie signing, redirect vetting and action flows and differ
+# only in where accounts live. The unit checks under a standalone Lua meet
+# luaossl and luaposix with deterministic stand-ins from the harness, so
+# they prove this script's own logic on any machine, tampered and expired
+# cookies turned away, header injection stripped, unsafe redirects refused
+# and the login flows answering as documented. The run through cgit itself
+# needs the real modules inside the binary's own Lua, so it is probed for,
+# and an unedited copy protects nothing, which is itself the behaviour worth
+# proving end to end.
+
+test_description='Check the shipped auth extensions'
+CGIT_TEST_NO_CREATE_REPOS=YesPlease
+. ./setup.sh
+. "$TEST_OUTPUT_DIRECTORY/extensions/lib.sh"
+
+interpreters=$(ext_lua_interpreters 4)
+test -z "$interpreters" &&
+	say 'no standalone lua on the path, unit checks skipped'
+
+for lua in $interpreters
+do
+	for variant in inline file
+	do
+		test_expect_success "auth-$variant checks under $lua" "
+			'$lua' '$EXT_TEST_DIRECTORY/test-auth.lua' \
+				'$EXTENSIONS_DIRECTORY/auth-$variant.lua' $variant
+		"
+	done
+done
+
+test_expect_success 'create a repository with one commit' '
+	test_create_repo repos/authy &&
+	(
+		cd repos/authy &&
+		echo content >file &&
+		git add file &&
+		git commit -m "guarded commit"
+	)
+'
+
+if test "$CGIT_HAS_LUA" -eq 1 &&
+	cgit_lua_probe "$PWD/repos/authy/.git" \
+		openssl.rand openssl.hmac posix.sys.stat posix.unistd
+then
+	test_set_prereq CGIT_LUA_AUTH
+else
+	say 'cgit lua lacks luaossl or luaposix, checks through cgit skipped'
+fi
+
+test_expect_success CGIT_LUA_AUTH 'point cgit at the unedited auth filter' '
+	cat >cgitrc <<-EOF
+	virtual-root=/
+	cache-size=0
+	auth-filter=lua:$EXTENSIONS_DIRECTORY/auth-inline.lua
+	repo.url=authy
+	repo.path=$PWD/repos/authy/.git
+	EOF
+'
+
+test_expect_success CGIT_LUA_AUTH 'an unedited copy protects nothing' '
+	cgit_url "authy/log/" >tmp &&
+	grep ">guarded commit</a>" tmp
+'
+
+test_done