# Functional Testing for Interactive Voice Response systems

We provide support for Interactive Voice Response (IVR) and Intelligent Virtual Agent (IVA) systems by leveraging Twilio to interact with them.

Most of the features from our standard functional testing work as normal for this, but there are some special features that we will cover in this guide.

For in-depth information on how our functional testing works, read here.

# Approach

Take a look at the following excerpt from a call made to the American Airlines IVR system.

Unlike Alexa or Google Assistant, where communication is done "in turns", an IVR call happens over a bi-directional line where each end can speak at any given time, so it is important to identify key moments during the call to translate that correctly into a test. From a caller perspective, the key moments in the call are:

  • Dialing the American Airlines number
  • Replying with our intention after the prompt "please, tell me what you're calling about"
  • Repeating our intention if the IVR system does not understand us
  • Pressing a number on the phone keypad if necessary

Here's the same call translated into one of our YAML tests:

- test: Call to American Airlines
- $DIAL: 
    - transcript: 
      - Thanks for calling American Airlines
      - Thanks for choosing American Airlines
      - Welcome to American Airlines
    - set finishOnPhrase: please tell me what you're calling about
- New flight reservation: 
    - transcript: Okay
    - set listeningTimeout: 10
    - set repeatOnPhrase: I didn't get that
- Yes: 
    - transcript: Excellent
    - set finishOnPhrase: if so press 1
- $1: Please wait while I transfer you to an agent

What happens here is we call the United Airlines number, which is set as part of our configuration file. We then have a back and forth interaction with the system - the first part of each line before the : is what we say to the system, such as "new flight reservation". The second part, which comes after the colon, contains assertions as well as additional configuration. We check the transcript property to verify the system's response is as expected. We set the finishOnPhrase to help us figure out when the system has finished speaking. These keywords and modifiers will be explained in the following sections.

If the expected response matches the actual response we receive from the system, then the test passes. Please note we use partial matches - so if the full response is "hi, how are you doing", a test that looks for "hi" will be considered a pass.

There is much more that can be done with our response assertions - you can read all about them here.

# Configuration

The following parameters are exclusive to IVR testing. They work in addition to the regular e2e configuration (opens new window).

Name Description Unit / Type Scope Default
finishOnPhrase Phrases that, when detected, will make the test continue to the next utterance. string, array Utterance
listeningTimeout The maximum time to listen to before sending the next utterance in seconds. Can be used instead of finishOnPhrase. seconds Global/Utterance 45
pauseBeforeUtterance Delay in seconds that is added before playing the current utterance. This delay comes after detecting a finishOnPhrase or reaching a listeningTimeout value, i.e., after the system finishes speaking. seconds Global/Utterance 1
phoneNumber Phone number to call to. Should be in the E.164 format (opens new window). number Global
recognitionHints Phrases that improve speech recognition for speech to text detection. string, array Utterance
recordCall Whether to record the call. If set to true, the URL for accessing the call will be provided as part of the response in the callAudioURL property. boolean Global false
repeatOnPhrase Repeats the previous utterance when one of these values is found. For cases when the system we are calling does not understand, for whatever reason, what was said. string, array Utterance
runInBand If set to true (default), a test suite will run only when the previous one has finished running. If set to false test suites will run in parallel to each other - defaults to true boolean Global true
sttThreshold A decimal number from 0 to 1 that represents the threshold applied when using fuzzy matching to identify a finishOnPhrase value. Setting this property to 1 means no fuzzy matching is applied. number Global 0.8

All Global parameters, except phoneNumber and runInBand should go inside a virtualDeviceConfig property inside your testing.json file if set:

    "phoneNumber": "PHONE_NUMBER",
    "runInBand": false,
    "virtualDeviceConfig": {
      "pauseBeforeUtterance": 1,
      "recordCall": false, 
      "repeatOnPhrase": [
        "Sorry I didn't get that",
        "Could you repeat that"
      "sttThreshold": 0.8
    "virtualDeviceToken": "phone-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"

These values can also be set inside a particular test file with a configuration section at the top of the file, like this:

  phoneNumber: "PHONE_NUMBER"
    - Sorry I didn't get that
    - Could you repeat that
  recordCall: false

"Utterance" level parameters are set inside each test with the use of the reserved keyword set.

Finally, IVR tests are always executed with a max response wait time of one minute per interaction.

# Special syntax

# The $DIAL Command

The $DIAL command is always the first command that we issue. It initiates the phone call to the specified phoneNumber.

# The "set" keyword

The set keyword is used to establish parameters that will alter the behavior of each interaction, it's also used to differentiate them from properties that will be verified (and not set) like transcript.

# Touch-tone entry

Touch-tone numbers can be entered by prefixing them with a $, like so:

- test: Call a touchtone service
- $DIAL: Welcome to Bespoken Enterprises. Press one for English, two for Spanish
- $2: Gracias y bienvenido

# Supported voices

As of today, voices from Google Text to Speech Service (opens new window), IBM Watson (opens new window), and Amazon Polly are supported. We do not support Twilio's own "Alice" voice. For a list of Amazon Polly voices that work with Twilio, take a look at the end of this article (opens new window).

If you need to use a custom voice, a good alternative is to use pre-recorded audios. To do this, simply replace your utterances for publicly available URLs containing the files you would like to use. Like this:

- test: Call to American Airlines
- $DIAL: 
    - transcript: Thanks for calling American Airlines
    - set finishOnPhrase: please tell me what you're calling about
- https://bespoken-samples.s3.amazonaws.com/audios/YES.wav: 
    - transcript: Okay
    - set listeningTimeout: 10
    - set repeatOnPhrase: I didn't get that
- https://bespoken-samples.s3.amazonaws.com/audios/NewFlightReservation.mp3: 
    - transcript: Excellent
    - set finishOnPhrase: if so press 1
- $1: Please wait while I transfer you to an agent

Information about supported audio formats can be found here (opens new window).

# BST Init

The bst init command is the fastest way to create all the files and folders needed to start testing your IVR system. It's a great starting point! You can read more about it here.

# Test Running Sequence - Parallelism

Individual tests run in the order in which they appear in their file. Test suites, however, run in random order and, by default, one after another. You can change this behavior by setting the runInBand property to false in your testing.json file, allowing test suites to run much faster and in parallel.

When enabling parallelism for IVR scripts, you don't need to define different virtual devices for your test suites, as multiple calls using the same phone virtual device are allowed.

Here's how test suites running in parallel looks like:


# Debugging and Troubleshooting

# Tracing output

Make sure "trace" is set to true in the testing.json file. This will output the complete back and forth of the test. It includes:

  • The message we send to the IVR system
  • The transcript of the response received

# Listening to call recordings

If recordCall is set to true, the response payload will include the callURL property. It contains the call recording in .wav format and will be shown as part of the bst command line output. Listening to it is a good way to understand why a test doesn't do well. Recordings are available for a week.

# Increasing the response wait time

IVR systems have interactions that vary in their length. When these go over the minute mark, you may find an error saying: Timeout exceeded while waiting for the interaction response. To fix this:

  • Make sure that you have set a correct finishOnPhrase value so that the test can move to the next interaction correctly
  • If you are using the listeningTimeout property instead, check that the value has been set to a value lower than 60 seconds
  • Finally, if the interaction is sure to last more than a minute, set the property maxAsyncE2EWaitTime in your testing.json file to a value higher than the default of 60000 ms. This will allow your tests to wait longer for a response before timing out.

# Improving transcript accuracy

Transcripts that are evaluated in our tests come from doing speech to text detection over the call streaming. To improve their accuracy, transcript, finishOnPhrase, and repeatOnPhrase values are sent to Google's speech recognition service as "hints" of what we are expecting to get back. While this is usually enough to get correct transcripts, those three properties are usually short and can also accept regular expressions that won't work as hints. For example, the star here could be used as a placeholder for "calling" and "choosing":

- $DIAL: 
  - transcript: Thanks for * American Airlines
  - set finishOnPhrase: Please tell me what you're calling about

If you want the most accurate transcripts possible, you can help the speech to text process by setting up the recognitionHints property like this:

- $DIAL: 
  - transcript: Thanks for * American Airlines
  - set finishOnPhrase: please tell me what you're calling about
  - set recognitionHints: 
    - Thanks for calling American Airlines. In a few words, please tell me what you're calling about.
    - Thanks for choosing American Airlines. In a few words, please tell me what you're calling about.

When this is set, the recognitionHints values will be the only values sent to Google's speech to text. The more detailed they are, the better the results will be.

# Matching finishOnPhrase values

By default, we apply fuzzy matching on finishOnPhrase values to identify the end of an interaction. Fuzzy matching means that we look for a value that is not identical but "similar enough" to the supplied value; we do this to bypass ocassional speech-to-text mismatches that could prevent call interactions from continuing. The confidence level that we use is controlled by the sttThreshold property, which allows for a numeric value between 0 and 1 . The default value is 0.8; setting it lower is more forgiving with the transcripts, while setting it to 1 makes the tests look for the exact value that was defined as a finishOnPhrase.

# Adding pauses before speaking

Our tests are programmed so that the next utterance plays after detecting a finishOnPhrase or reaching a listeningTimeout. On rare occasions, this happens before your system is ready to receive the next instruction. To better adjust these times, you can use the pauseBeforeUtterance property at the utterance level. Eg:

- test : Cancel a reservation
- $DIAL :
  - prompt : Welcome to the American Airlines
  - set finishOnPhrase : please tell me what you're calling about
- Cancellations: 
  - prompt: what's your four digit booking code
  - set pauseBeforeUtterance: 2

In the example above, we dial the American Airlines contact center and, as soon as we hear "please tell me what you're calling about", we'll wait 2 seconds before saying "Cancellations".

# Project Sample

You can find the American Airlines tests we used in this page here (opens new window).