diff --git a/.gitignore b/.gitignore
index 79f80c3..69f4dfa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,4 +7,3 @@ luac
 *.so
 
 include/
-test.lua
diff --git a/test.lua b/test.lua
new file mode 100644
index 0000000..29396db
--- /dev/null
+++ b/test.lua
@@ -0,0 +1,277 @@
+--[[
+    Tests for Callisto
+    Run with:
+       ./csto test.lua
+
+    A test should use the smallest amount of functions possible,
+    and should not rely on facilities such as os.execute to complete
+    its task. Using functions in the same library is acceptable, but
+    Callisto facilities in different libraries should not be used.
+
+    Licensed to the public domain
+]]--
+
+local oldenv = _ENV
+
+local function test(f)
+	local _ENV = oldenv
+	local function mesg(...)
+		io.stdout:write(..., '\n')
+	end
+
+	assert(type(f) == "function")
+	mesg(f())
+end
+
+-- Table containing tests for each library.
+-- The cl library is excluded from here as it is almost
+-- impossible to test without user interaction.
+local tests = {
+	environ = {
+		getvar = function ()
+			local var = "HOME"
+
+			assert(environ[var])
+			return 'environ["' .. var .. '"] ~= nil'
+		end,
+		setvar = function ()
+			local var = "VAR"
+			local val = "hello"
+
+			environ[var] = val
+			assert(environ[var] == "hello")
+			return 'environ["' .. var .. '"] = "' .. val .. '"'
+		end
+	},
+
+	extra = {
+	},
+
+	fs = {
+		copy = function ()
+			local src, dst = "testfile", "testfile.cp"
+			local contents = "hello, world!"
+			local f, err = io.open(src, 'w')
+
+			assert(f, err)
+
+			f:write(contents)
+			f:close()
+
+			assert(fs.copy(src, dst))
+			assert(io.input(dst):read('a') == contents)
+
+			assert(fs.remove(src))
+			assert(fs.remove(dst))
+
+			return 'fs.copy("' .. src .. '", "' .. dst .. '")'
+		end,
+		directory = function ()
+			local dir, subdir = "testdir", "testdir/sub"
+
+			assert(fs.mkdir(dir))
+			assert(fs.exists(dir) and fs.isdirectory(dir))
+			assert(fs.rmdir(dir))
+			assert(fs.mkdir(subdir, true))
+
+			assert(fs.exists(dir))
+			assert(fs.isdirectory(dir))
+			assert(fs.exists(subdir))
+			assert(fs.isdirectory(subdir))
+
+			assert(fs.rmdir(subdir))
+			assert(fs.rmdir(dir))
+
+			return ([[
+fs.mkdir("%s")
+fs.rmdir("%s")
+fs.mkdir("%s", true)
+fs.rmdir("%s"")
+fs.rmdir("%s")]]):format(
+				dir,
+				dir,
+				subdir,
+				subdir,
+				dir
+			)
+		end,
+		move = function ()
+			local src, dst = "testfile", "testfile.new"
+			local contents = "hello, world!"
+			local f, err = io.open(src, 'w')
+
+			assert(f, err)
+
+			f:write(contents)
+			f:close()
+
+			assert(fs.move(src, dst))
+			assert(io.input(dst):read('a') == contents)
+
+			assert(fs.remove(dst))
+
+			return 'fs.move("' .. src .. '", "' .. dst .. '")'
+		end,
+		path = function ()
+			local bpath, base = "/etc/fstab", "fstab"
+			local dpath, dir = "/usr/local/bin", "/usr/local"
+
+			assert(fs.basename(bpath) == base)
+			assert(fs.dirname(dpath) == dir)
+
+			return 'fs.basename("' .. bpath .. [[")
+fs.dirname("]] .. dpath .. '")'
+		end,
+		remove = function ()
+			local file = "testfile"
+			local f, err = io.open(file, 'w')
+
+			assert(f, err)
+
+			f:write("")
+			f:close()
+
+			assert(fs.remove(file))
+
+			return 'fs.remove("' .. file .. '")'
+		end,
+		workdir = function ()
+			local d = "/usr"
+			local wd = fs.workdir()
+
+			fs.workdir(d)
+			assert(fs.workdir() == d)
+			fs.workdir(wd)
+			assert(fs.workdir() == wd)
+			return 'fs.workdir("' .. d .. '")'
+		end
+	},
+
+	-- basic tests for lua-cjson; this is not
+	-- my library so I won't test it extensively
+	json = {
+		decode = function()
+			local o = [[
+"hello": "world",
+"n": 4,
+"fpn": 2.4444449,
+"a": [1, 2, 4, 8, 16]
+]]
+			local j = [[
+{
+	]] .. o .. [[,
+	"o": {
+		]] .. o .. [[
+	}
+}
+]]
+
+			local t = json.decode(j)
+
+			for _, t in ipairs {t, t.o} do
+				assert(t.hello == "world")
+				assert(t.n == 4)
+				assert(t.fpn == 2.4444449)
+				assert(t.a[1] == 1)
+				assert(t.a[2] == 2)
+				assert(t.a[3] == 4)
+				assert(t.a[4] == 8)
+				assert(t.a[5] == 16)
+			end
+
+			return "json.decode('" .. j:gsub("%s", "") .. "')"
+		end,
+		encode = function()
+			local o = {
+				hello = "world",
+				n = 4,
+				fpn = 2.4444449,
+				a = {1, 2, 4, 8, 16}
+			}
+
+			local j = json.encode(o)
+			local t = json.decode(j)
+
+			assert(t.hello == "world")
+			assert(t.n == 4)
+			assert(t.fpn == 2.4444449)
+			assert(t.a[1] == 1)
+			assert(t.a[2] == 2)
+			assert(t.a[3] == 4)
+			assert(t.a[4] == 8)
+			assert(t.a[5] == 16)
+
+			return "json.decode(json.encode({...}))"
+		end
+	},
+
+	os = {
+		hostname = function ()
+			assert(os.hostname())
+			return "os.hostname()"
+		end
+	},
+
+	process = {
+		pid = function ()
+			assert(math.type(process.pid()) == "integer")
+			return "process.pid()"
+		end,
+		pidof = function ()
+			local proc = "csto"
+
+			assert(math.type(process.pidof(proc)) == "integer")
+			return 'process.pidof("' .. proc .. '")'
+		end,
+		signum = function ()
+			local sig = "SIGKILL"
+
+			-- probably signal no.9
+			assert(math.type(process.signum(sig)) == "integer")
+			return 'process.signum("' .. sig .. '")'
+		end,
+		send = function ()
+			local hdl = io.popen("sleep 8")
+			local pid = process.pidof("sleep")
+
+			assert(process.send(pid, "SIGKILL"))
+			hdl:close()
+
+			return "process.send(" .. tostring(pid) .. ', "SIGKILL")'
+		end
+	}
+}
+
+-- Run all tests.
+do
+	local env = tests
+	env.test = test
+	local _ENV = env
+
+	-- environ
+	test(environ.getvar)
+	test(environ.setvar)
+
+	-- fs
+	test(fs.copy)
+	test(fs.directory)
+	test(fs.move)
+	test(fs.path)
+	test(fs.remove)
+	test(fs.workdir)
+
+	-- json
+	test(json.decode)
+	test(json.encode)
+
+	-- os
+	test(os.hostname)
+
+	-- process
+	test(process.pid)
+	test(process.pidof)
+	test(process.signum)
+	test(process.send)
+end
+
+cl.mesg("all tests completed successfully")