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A distributed phone call test program

Project description

This program connects to an Asterisk server and performs call tests, i.e. it causes one channel to call another and verifies that the call worked.

CallTest implements a small JSON server. You can use it with your favorite monitoring system to check test results, or to manually trigger a test from some web site or via curl.

This package is a work in progress. Some planned features are not yet implemented. Also, this README needs to be expanded and split up. Volunteers welcome.


The configuration is a YAML file and basically looks like this:

    channel: "SIP/foo/{number}"
    number: "+49123456789"
    channel: "SIP/bar/{number}"
    number: "+49987654321"

    mode: dtmf

    src: foo
    dst: bar
    info: "Check that calling bar from foo works"

See example.cfg for a working version. Run ./ct -c example.cfg dumpcfg for a copy that’s been pre-filled with default values.


calls contains a number of (named) tests.

  • src: the source link to use, i.e. to originate the call.

  • dst: the destination to use, i.e. to answer the call.

  • mode: How to perform a test. See below.

  • timeout: Hard limit for a call’s duration. If a call exceeds this, it is terminated and the test fails.

  • url: for answer-only modes, you need a way to cause a call. For now this is done by fetching the data at this URL.

    This field may either be a simple URL, or a dictionary with these attributes:

    • url
    • method (GET POST PUT)
    • query
    • body

    query and body may contain a {number} substitution.

  • check_callerid: set to false to disable Caller ID verification.

The ‘:default:’ values are applied to all other entries (unless overridden), which saves you from changing 999 identical entries.

The test subheading contains values that are relevant for running repeated tests in the background:

  • retry, repeat: seconds to delay until repeating a call, depending on whether the previous attempt failed or succeeded.
  • warn: number of consecutive failures when the test enters “warn” state.
  • fail: number of consecutive failures when the test enters “fail” state.
  • skip: if True, this test can only be triggered manually.


The mode value configure how CallTest processes a call.


The answering channel sends a random sequence of DTMF tones. The originator then does the same thing. The receivers verify that the codes are correct.

When dtmf.may_repeat is set, the receiver is allowed to read duplicate DTMF tones. This flag might be necessary with in-band signalling.

dtmf.len is the number of digits to test. Typically, one digit will be repeated. The sequence is otherwise random.


The answering channel will acknowledge that it’s ringing, but then simply hang up.


Like DTMF, but both sides send a sound file instead. The sounds are recorded. They should match, somewhat, but that’s not yet tested.


Originate-only: call this number. It should be RINGING. Then hang up.


Originate-only: call this number. It should answer. Play a sound, then hang up.

If no audio.src_out sound is specified, simply hang up.

Optionally, audio.dst_in records incoming audio during the call. Recording runs while the outgoing sound is playing.



Originate-only: call this number. The call may not go through. It must be rejected, some time before ringtime.

Also TODO: Add a flag to determine whether an intermediate Ringing state is allowed / required / prohibited.



Originate-only: call this number. The call may not go through. It must be RINGing and then be rejected between ringtime and timeout seconds later.


Answer-only: wait for an incoming call, set it to RINGING, wait a few seconds, hang up.


Answer-only: wait for an incoming call, answer it, optionally play a sound, optionally² record audio while the sound is playing, then hang up.


Answer-only: wait for an incoming call, answer it, optionally play a sound, optionally record incoming audio until the originator hangs up or presses #.

The recording will be overlaid with the outgoing sound. This is an Asterisk limitation.

Number format

CallTest recognizes two kinds of phone numbers: site-local extensions, and everything else. CallTest distinguishes these by the initial ‘+’.


The outgoing Asterisk channel should be able to handle both kinds directly. If not, you need to write a “Local” channel that mangles the dialled number. For instance, if you need to drop the ‘+’, use this macro:

context mangle {
    _+! => Dial(SIP/broken/${EXTEN:1});

and then call Local/{number}@mangle. As another example, if you need to use lcoal number format to dial out:

context mangle {
    _X! => Dial(SIP/broken/${EXTEN});  // pass-thru for local extensions
    _+49123! => Dial(SIP/broken/${EXTEN:6});  // 49123: country+city
    _+49! => Dial(SIP/broken/0${EXTEN:3});  // 49: country; 0: national prefix
    // _+! => Dial(SIP/broken/00${EXTEN:1}); // 00: international prefix
    _+! => Congestion();

though you can probably get by with just the first and last line.

If you’re in the NANP (USA or Canada), you probably want to use this macro instead:

context mangle {
    _N! => Dial(SIP/broken/1888${EXTEN});  // 888 is your area code
    _[01]! => Dial(SIP/broken/${EXTEN});  // pass-thru for operator and long-distance
    _+1! => Dial(SIP/broken/${EXTEN:1});  // long distance
    // _+! => Dial(SIP/broken/011${EXTEN:1});  // international
    _+! => Congestion();

The last line causes a “Congestion” blocker so that a mistake won’t cause international charges.


CallTest will verify that the caller’s number on an incoming call matches the number in the test’s configuration’s source link. If that number is prefixed with a ‘+’, the incoming number is converted to international format and needs to match exactly. Otherwise, the configured number is assumed to be a local extension and must only be at the end of the caller’s.

This ensures that there’s no incoming nonsense, while acknowledging that site-local numbers often are not transmitted cleanly.

If you need Asterisk to mangle the caller’s number so that it looks sane enough for CallTest, add that to the calltest macro. For instance, if your phone system adds a leading “get a trunk line” zero (in the NANP it’s usually a 9) to incoming calls, you’d do this:

macro calltest(typ) {
    switch(cid) {
        pattern 0.:
    Stasis("calltest", ${typ});

We know that it’s annoying to have to play with Asterisk’s dialplans for this. If you want to add a pattern-match-based number manglich scheme to CallTest, great, we’ll gladly accept a pull request. However, “sane” modern phone systems should work fine with the default setting.

Asterisk configuration

Server connection

Some parameters in the asterisk section require further elucidation.

  • app:
  • audio: (the base of) the “sound” URL which Asterisk will use to find your test’s outgoing sound files. Should be sound:/some/absolute/path.

Test setup

Asterisk needs to know how to direct incoming calls to the tester. This is typically done with a Stasis macro. This is for extensions.ael:

macro calltest(link,nr) {
  • calltest: the config parameter.
  • link: the name of the link, in
  • nr: the incoming destination phone number.

You’d call this macro from your context:

1234 => &calltest(foo,${EXTEN});

If you want to route all incoming calls on a channel to this macro, use something like this context:

context ext_bar {
     s => &calltest(bar,);
     i => &calltest(bar,${INVALID_EXTEN});
     _+! => &calltest(bar,${EXTEN});
     _X! => &calltest(bar,${EXTEN});
     h => Hangup();


These calls all have no spaces after the argument-separating commas.
This is important.

Line setup

PJSIP is not very forgiving. Sample config: TODO.

In lieu of voice quality checking, which this system does not yet do, you might want to simply set your endpoints’ DTMF mode to “inband”. Don’t use a compressing codec when you do this. You might need to set the test’s dtmf_may_repeat option. However, in-band DTMF is not particularly reliable and may break randomly.

The random DTMF sequence only uses digits because letters are not universally passed on, while # and * may be interpreted and thus swallowed by intermediate systems.


This package contains an example.cfg configuration. To use it, your asterisk.ael file should contain these lines:

macro calltest(link, nr) {

context direct {
    _.! => &calltest(${EXTEN},);

    answer => {
    ringing => {
    progress => {

Add this to your ari.conf:

[example] type = user password = oh_no_you_do_not password_format = plain

Finally, add enabled=yes to the [general] section of http.conf.

After doing all of this and restarting your Asterisk (reloading “ael”, “http” and “res_ari” should work too), the command ./ct -c example.cfg run should pass.

Web service endpoints

  • /

    List state and failed tests.

  • /list

    Like / but als lists successful tests.

  • /test/name

    Status for this test.

  • /test/name/start (PUT)

    Start this test.

  • /test/name/stop (PUT)

    Interrupt this test.

  • /test/name/fail (PUT)

    Interrupt this test, mark the run as failed.

  • /ws (web socket)

    Monitors the tester. Input on the websocket is discarded.

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