TestReqID (FIX tag 112)

StringFIX 4.4FIX 4.2FIX 5.0 SP2

TestReqID (tag 112) is a String field defined in FIX 4.4, FIX 4.2 and FIX 5.0 SP2. It appears in 2 message types and is required in 1 of them.

At a glance

Tag: 112
Name: TestReqID
Datatype: String
Dialects: FIX 4.4, FIX 4.2 and FIX 5.0 SP2
Messages: 2

What the specification says

FIX 4.4

Identifier included in Test Request message to be returned in resulting Heartbeat

FIX 4.2

Identifier included in Test Request message to be returned in resulting Heartbeat

FIX 5.0 SP2

Identifier included in TestRequest(35=1) message to be returned by the peer in a Heartbeat(35=0) message as a response.

Descriptions are quoted from the FIX Orchestra sources under the Apache 2.0 licence.

A real message using tag 112

Heartbeat · FIX 4.4

Tag	Field	Wire value	Meaning
8	BeginString	FIX.4.4
9	BodyLength	75
35	MsgType	0	Heartbeat
49	SenderCompID	BOARTEAM
56	TargetCompID	COUNTERPARTY
34	MsgSeqNum	2
52	SendingTime	20240101-12:00:00.000
112	TestReqID	EXAMPLE
10	CheckSum	143

Edit and decode it yourself

Shown with | separators for readability. On the wire FIX uses SOH (0x01), an invisible control byte — and because BodyLength and CheckSum are computed over the actual bytes, the two forms have different checksums. Both are valid and both decode here.

Open in the full decoder →

Generated from the FIX 4.4 dictionary and verified at build time: it parses and validates with no issues. Open the decoder to try your own message.

Where tag 112 appears

Requiredness is a property of the message, not of the field: the same tag can be optional in one message and conditionally required in another.

Message	MsgType	FIX 4.4	FIX 4.2	FIX 5.0 SP2	Where in the message
Heartbeat	0	Optional	Optional	Optional	directly on the message body
TestRequest	1	Required	Required	Required	directly on the message body

Wire format

Free-form text. Any byte except the SOH separator is legal, so values are not trimmed or case-folded on the wire. @boarteam/fix keeps the value as a string; format rules are checked by validate(), which reports validate/invalid-value rather than throwing.

Read tag 112 in TypeScript

decode.tsts

import { createFixEngine } from "@boarteam/fix";import { dictionary } from "@boarteam/fix-dict-fix44";const fix = createFixEngine(dictionary);const { message, issues } = fix.parse(raw);const field = message.fields[112];field?.name;   // "TestReqID"field?.raw;    // the verbatim wire stringfield?.value;  // coerced to a string

Decode this in your own code

The same engine that produced the decoded example above is an Apache-2.0 npm package with zero runtime dependencies. It runs in Node and in the browser, and parse() returns problems as data instead of throwing.

npm i @boarteam/fix @boarteam/fix-dict-fix44

Try the decoder Source on GitHub