diff --git a/tests/runalltests.nim b/tests/runalltests.nim
new file mode 100644
index 0000000..5349d2d
--- /dev/null
+++ b/tests/runalltests.nim
@@ -0,0 +1,4 @@
+{.used.}
+
+import testdatachannel
+import teststun
diff --git a/tests/teststun.nim b/tests/teststun.nim
index f22ebfb..5b3f034 100644
--- a/tests/teststun.nim
+++ b/tests/teststun.nim
@@ -1,11 +1,33 @@
+import options
 import ../webrtc/stun/stun
+import ../webrtc/stun/stun_attributes
 import ./asyncunit
-import binary_serialization
 
 suite "Stun suite":
-  test "Stun encoding/decoding with padding":
+  test "Stun decoding":
     let msg = @[ 0x00'u8, 0x01, 0x00, 0xa4, 0x21, 0x12, 0xa4, 0x42, 0x75, 0x6a, 0x58, 0x46, 0x42, 0x58, 0x4e, 0x72, 0x6a, 0x50, 0x4d, 0x2b, 0x00, 0x06, 0x00, 0x63, 0x6c, 0x69, 0x62, 0x70, 0x32, 0x70, 0x2b, 0x77, 0x65, 0x62, 0x72, 0x74, 0x63, 0x2b, 0x76, 0x31, 0x2f, 0x62, 0x71, 0x36, 0x67, 0x69, 0x43, 0x75, 0x4a, 0x38, 0x6e, 0x78, 0x59, 0x46, 0x4a, 0x36, 0x43, 0x63, 0x67, 0x45, 0x59, 0x58, 0x58, 0x2f, 0x78, 0x51, 0x58, 0x56, 0x4c, 0x74, 0x39, 0x71, 0x7a, 0x3a, 0x6c, 0x69, 0x62, 0x70, 0x32, 0x70, 0x2b, 0x77, 0x65, 0x62, 0x72, 0x74, 0x63, 0x2b, 0x76, 0x31, 0x2f, 0x62, 0x71, 0x36, 0x67, 0x69, 0x43, 0x75, 0x4a, 0x38, 0x6e, 0x78, 0x59, 0x46, 0x4a, 0x36, 0x43, 0x63, 0x67, 0x45, 0x59, 0x58, 0x58, 0x2f, 0x78, 0x51, 0x58, 0x56, 0x4c, 0x74, 0x39, 0x71, 0x7a, 0x00, 0xc0, 0x57, 0x00, 0x04, 0x00, 0x00, 0x03, 0xe7, 0x80, 0x2a, 0x00, 0x08, 0x86, 0x63, 0xfd, 0x45, 0xa9, 0xe5, 0x4c, 0xdb, 0x00, 0x24, 0x00, 0x04, 0x6e, 0x00, 0x1e, 0xff, 0x00, 0x08, 0x00, 0x14, 0x16, 0xff, 0x70, 0x8d, 0x97, 0x0b, 0xd6, 0xa3, 0x5b, 0xac, 0x8f, 0x4c, 0x85, 0xe6, 0xa6, 0xac, 0xaa, 0x7a, 0x68, 0x27, 0x80, 0x28, 0x00, 0x04, 0x79, 0x5e, 0x03, 0xd8 ]
-    check msg == encode(StunMessage.decode(msg))
+    let stunmsg = StunMessage.decode(msg)
+    check:
+      stunmsg.msgType == 1
+      stunmsg.transactionId.len() == 12
+      stunmsg.attributes.len() == 6
+      stunmsg.attributes[0].attributeType == 6 # AttrUsername
+      stunmsg.attributes[^1].attributeType == 0x8028 # AttrFingerprint
+
+  test "Stun encoding":
+    let transactionId: array[12, byte] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
+    var msg = StunMessage(msgType: 0x0001'u16, transactionId: transactionId)
+    msg.attributes.add(ErrorCode.encode(ECUnknownAttribute))
+    let encoded = msg.encode()
+    let decoded = StunMessage.decode(encoded)
+    # cannot do `check msg == decoded` because encode add a
+    # Fingerprint at the end of the attributes
+    check:
+      decoded.msgType == 1
+      decoded.transactionId == transactionId
+      decoded.attributes.len() == 2
+      decoded.attributes[0].attributeType == 9 # AttrErrorCode
+      decoded.attributes[^1].attributeType == 0x8028 # AttrFingerprint
 
   test "Error while decoding":
     let msgLengthFailed = @[ 0x00'u8, 0x01, 0x00, 0xa4, 0x21, 0x12, 0xa4, 0x42, 0x75, 0x6a, 0x58, 0x46, 0x42, 0x58, 0x4e, 0x72, 0x6a, 0x50, 0x4d ]
diff --git a/webrtc.nimble b/webrtc.nimble
index dd3d318..57f3360 100644
--- a/webrtc.nimble
+++ b/webrtc.nimble
@@ -33,4 +33,4 @@ proc runTest(filename: string) =
   rmFile "tests/" & filename.toExe
 
 task test, "Run test":
-  runTest("testdatachannel")
+  runTest("runalltests")
diff --git a/webrtc/stun/stun.nim b/webrtc/stun/stun.nim
index 3248d53..dcb785d 100644
--- a/webrtc/stun/stun.nim
+++ b/webrtc/stun/stun.nim
@@ -59,10 +59,9 @@ type
 
   RawStunMessage = object
     msgType: uint16
-    # it.conten.len() + 8 Because the Fingerprint is added after the encoding
     length* {.bin_value: it.content.len().}: uint16
     magicCookie: uint32
-    transactionId: array[12, byte]
+    transactionId: array[12, byte] # Down from 16 to 12 bytes in RFC5389
     content* {.bin_len: it.length.}: seq[byte]
 
   StunMessage* = object
@@ -98,11 +97,11 @@ proc decode*(T: typedesc[StunMessage], msg: seq[byte]): StunMessage =
            transactionId: smi.transactionId,
            attributes: RawStunAttribute.decode(smi.content))
 
-proc encode*(msg: StunMessage, userOpt: Option[seq[byte]]): seq[byte] =
+proc encode*(msg: StunMessage, userOpt: Option[seq[byte]] = none(seq[byte])): seq[byte] =
   const pad = @[0, 3, 2, 1]
   var smi = RawStunMessage(msgType: msg.msgType,
-                             magicCookie: magicCookie,
-                             transactionId: msg.transactionId)
+                           magicCookie: magicCookie,
+                           transactionId: msg.transactionId)
   for attr in msg.attributes:
     smi.content.add(Binary.encode(attr))
     smi.content.add(newSeq[byte](pad[smi.content.len() mod 4]))