diff --git a/api.spec.lua b/api.spec.lua
new file mode 100644
index 0000000..a9f9d2f
--- /dev/null
+++ b/api.spec.lua
@@ -0,0 +1,12 @@
+mtt.register("send mail", function(callback)
+    -- send a mail
+    local success, err = mail.send({from = "player1", to = "player2", subject = "something", body = "blah"})
+    assert(success)
+    assert(not err)
+
+    -- check the receivers inbox
+    local entry = mail.get_storage_entry("player2")
+    assert(entry)
+    assert(#entry.inbox > 0)
+    callback()
+end)
diff --git a/init.lua b/init.lua
index 2f635f2..452c8f2 100644
--- a/init.lua
+++ b/init.lua
@@ -61,4 +61,7 @@ mail.migrate()
 
 if minetest.get_modpath("mtt") then
 	dofile(MP .. "/mtt.lua")
+	dofile(MP .. "/api.spec.lua")
+	dofile(MP .. "/util/uuid.spec.lua")
+	dofile(MP .. "/util/normalize.spec.lua")
 end
diff --git a/mtt.lua b/mtt.lua
index f5cb124..7c8cf0b 100644
--- a/mtt.lua
+++ b/mtt.lua
@@ -1,15 +1,10 @@
-mtt.register("send mail", function(callback)
-    -- create "player2"
+
+mtt.register("setup", function(callback)
+    -- create test players
     local auth_handler = minetest.get_auth_handler()
+    auth_handler.set_password("player1", "")
     auth_handler.set_password("player2", "")
+    auth_handler.set_password("player3", "")
 
-    -- send a mail
-    local success, err = mail.send({from = "player1", to = "player2", subject = "something", body = "blah"})
-    assert(success)
-    assert(not err)
-
-    -- check the receivers inbox
-    local entry = mail.get_storage_entry("player2")
-    assert(entry ~= nil and #entry.inbox > 0)
     callback()
-end)
+end)
\ No newline at end of file
diff --git a/storage.lua b/storage.lua
index a0e8e93..470b9a9 100644
--- a/storage.lua
+++ b/storage.lua
@@ -1,23 +1,29 @@
 -- storage getter/setter
 
+-- create or populate empty fields on an entry
+local function populate_entry(e)
+	e = e or {}
+	e.contacts = e.contacts or {}
+	e.inbox = e.inbox or {}
+	e.outbox = e.outbox or {}
+	e.lists = e.lists or {}
+	return e
+end
+
 function mail.get_storage_entry(playername)
 	local str = mail.storage:get_string(playername)
 	if str == "" then
 		-- new entry
-		return {
-			contacts = {},
-			inbox = {},
-			outbox = {},
-			lists = {}
-		}
+		return populate_entry()
 	else
 		-- deserialize existing entry
-		return minetest.parse_json(str)
+		local e = minetest.parse_json(str)
+		return populate_entry(e)
 	end
 end
 
 function mail.set_storage_entry(playername, entry)
-	mail.storage:get_string(playername, minetest.write_json(entry))
+	mail.storage:set_string(playername, minetest.write_json(entry))
 end
 
 -- get a mail by id from the players in- or outbox
diff --git a/storage.spec.lua b/storage.spec.lua
new file mode 100644
index 0000000..e44dd15
--- /dev/null
+++ b/storage.spec.lua
@@ -0,0 +1,39 @@
+
+mtt.register("storage", function(callback)
+    -- sanity checks
+    local playername = "player1"
+    local entry = mail.get_storage_entry(playername)
+    assert(entry)
+
+    -- create
+    local contact = {
+        name = "other-player",
+        note = "my-note"
+    }
+    mail.update_contact(playername, contact)
+
+    -- read
+    local contacts = mail.get_contacts(playername)
+    assert(#contacts == 1)
+    assert(contacts[1].note == contact.note)
+    assert(contacts[1].name == contact.name)
+
+    -- update
+    mail.update_contact(playername, {
+        name = contact.name,
+        note = "xy"
+    })
+
+    -- read updated
+    contacts = mail.get_contacts(playername)
+    assert(#contacts == 1)
+    assert(contacts[1].note == "xy")
+    assert(contacts[1].name == contact.name)
+
+    -- delete
+    mail.delete_contact(playername, contact.name)
+    contacts = mail.get_contacts(playername)
+    assert(#contacts == 0)
+
+    callback()
+end)
\ No newline at end of file
diff --git a/test/minetest.conf b/test/minetest.conf
index 992f787..afea5f2 100644
--- a/test/minetest.conf
+++ b/test/minetest.conf
@@ -1,3 +1,4 @@
 default_game = minetest_game
 mg_name = v7
-mtt_enable = true
\ No newline at end of file
+mtt_enable = true
+mtt_filter = mail
\ No newline at end of file
diff --git a/util/normalize.spec.lua b/util/normalize.spec.lua
new file mode 100644
index 0000000..88628ad
--- /dev/null
+++ b/util/normalize.spec.lua
@@ -0,0 +1,12 @@
+
+mtt.register("util/normalize_players_and_add_recipients", function(callback)
+    local recipients = {}
+    local undeliverable = {}
+    local to = mail.normalize_players_and_add_recipients("player1,player2", recipients, undeliverable)
+
+    assert(to == "player1, player2")
+    assert(not next(undeliverable))
+    assert(recipients["player1"])
+    assert(recipients["player2"])
+    callback()
+end)
\ No newline at end of file
diff --git a/util/uuid.spec.lua b/util/uuid.spec.lua
new file mode 100644
index 0000000..549399e
--- /dev/null
+++ b/util/uuid.spec.lua
@@ -0,0 +1,7 @@
+
+
+mtt.register("uuid", function(callback)
+    assert(mail.new_uuid())
+    assert(mail.new_uuid() ~= mail.new_uuid())
+    callback()
+end)
\ No newline at end of file