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    Federated accessibility test automation


    Testaro is a collection of collections of web accessibility tests.

    The purpose of Testaro is to provide programmatic access to 1228 accessibility tests defined in several test packages and in Testaro itself.

    System requirements

    Version 14 or later of Node.js.


    Testaro uses:

    • Playwright to launch browsers, perform user actions in them, and perform tests
    • pixelmatch to measure motion

    Testaro includes some of its own accessibility tests. In addition, it performs the tests in:

    Some of the Testaro tests are derived from tests performed by the BBC Accessibility Standards Checker.

    As of this version, the counts of tests in the packages referenced above were:

    • Alfa: 103
    • Axe-core: 138
    • Continuum Community Edition: 267
    • Equal Access: 163
    • HTML CodeSniffer: 98
    • Tenon: 180
    • WAVE: 110
    • Nu Html Checker: 147
    • subtotal: 612
    • Testaro tests: 22
    • grand total: 1228

    Code organization

    The main directories containing code files are:

    • package root: main code files
    • tests: files containing the code defining particular tests
    • procs: shared procedures
    • validation: code and artifacts for the validation of Testaro


    Some of the dependencies of Testaro are published as Github packages. Installing Testaro therefore requires you to be authorized to read Github packages. If you do not yet have that authorization, you can give it to yourself as follows:

    • Log in at Github.

    • From your avatar in the upper-right corner, choose “Settings”.

    • In the left sidebar, choose “Developer settings”.

    • In the left sidebar, choose “Personal access tokens”.

    • Activate the button “Generate new token”.

    • Give the new token a descriptive note.

    • Select an expiration date.

    • Check the checkbox read:packages.

    • Activate the button “Generate token”.

    • Copy the generated token (you can use the copy icon next to it).

    • In the local directory of the project into which you will install Testaro, create a file named .npmrc, unless it already exists.

    • Populate the .npmrc file with the following statements, replacing abc with your Github username and xyz with the token that you copied:


    Once you have done that, you can install Testaro as you would install any npm package.


    All of the tests that Testaro can perform are free of cost, except those in the Tenon and WAVE packages. The owner of each of those packages gives new registrants a free allowance of credits before it becomes necessary to pay for use of the API of the package. The required environment variables for authentication and payment are described below under “Environment variables”.


    To use Testaro, you must specify what it should do. You do this with a script and optionally a batch.



    To use Testaro, you provide a script to it. The script contains commands. Testaro runs the script, i.e. performs the commands in it and writes a report of the results.

    A script is a JSON file with the properties:

      "id": "string consisting of lower-case ASCII letters and digits",
      "what": "string: description of the script",
      "strict": "boolean: whether redirections should be treated as failures",
      "timeLimit": "number: limit in seconds on the execution of this script",
      "commands": "array of objects: the commands to be performed"

    The timeLimit property is optional. If it is omitted, a default of 300 seconds (5 minutes) is set.


    Here is an example of a script:

      "id": "samplescript",
      what: "Test with alfa",
      strict: true,
      timeLimit: 65,
      commands: [
          type: "launch",
          which: "chromium",
          what: "Chromium browser"
          type: "url",
          which: "",
          what: "page with a few accessibility defects"
          type: "test",
          which: "alfa",
          what: "Siteimprove alfa package"

    This script tells Testaro to open a page in the Chromium browser, navigate to, and perform the tests in the alfa package on that URL.


    If the strict property is true, Testaro will accept redirections that add or subtract a final slash, but otherwise will treat redirections as failures.



    The commands property’s value is an array of command objects.

    Each command has a type property and optionally has a name property (used in branching, described below). It must or may have other properties, depending on the value of type.

    Command sequence

    The first two commands in any script have the types launch and url, respectively, as shown in the example above. They launch a browser and then use it to visit a URL. For example:

      "type": "launch",
      "which": "chromium",
      "what": "Open a page in a Chromium browser"
      "type": "url",
      "which": "",
      "what": "English Wikipedia home page"

    Command types

    The subsequent commands can tell Testaro to perform any of:

    • moves (clicks, text inputs, hovers, etc.)
    • navigations (browser launches, visits to URLs, waits for page conditions, etc.)
    • alterations (changes to the page)
    • tests (whether in dependency packages or defined within Testaro)
    • branching (continuing from a command other than the next one)

    An example of a move is:

      "type": "radio",
      "which": "No",
      "index": 2,
      "what": "No, I am not a smoker"

    In this case, Testaro checks the third radio button whose text includes the string “No” (case-insensitively).

    In identifying the target element for a move, Testaro matches the which property with the texts of the elements of the applicable type (such as radio buttons). It defines the text of an input element as the concatenated texts of its implicit label or explicit labels, if any, plus, for the first input in a fieldset element, the text content of the legend element of that fieldset element. For any other element, Testaro defines the text as the text content of the element.

    When multiple elements of the same type have indistinguishable texts, you can include an index property to specify the index of the target element, among all those that will match.


    An example of a navigation is the command of type url above.

    Once you have included a url command in a script, you do not need to add more url commands unless you want the browser to visit a different URL.

    However, some tests modify web pages. In those cases, Testaro inserts additional url commands into the script property of the options object, after those tests, to ensure that changes made by one test do not affect subsequent acts.

    Another navigation example is:

      "type": "wait",
      "which": "travel",
      "what": "title"

    In this case, Testaro waits until the page title contains the string “travel” (case-insensitively).


    An example of an alteration is:

      "type": "reveal",
      "what": "make everything visible"

    This command causes Testaro to alter the display and visibility style properties of all elements, where necessary, so those properties do not make any element invisible.


    The possible commands of type test are enumerated in the tests object defined in the index.js file.


    An example of a packaged test is:

      "type": "test",
      "which": "wave",
      "reportType": 1,
      "what": "WAVE summary"

    In this case, Testaro runs the WAVE test with report type 1.

    An example of a Testaro-defined test is:

      "type": "test",
      "which": "motion",
      "delay": 1500,
      "interval": 2000,
      "count": 5,
      "what": "test for motion on the page"

    In this case, Testaro runs the motion test with the specified parameters.


    The tenon test requires two commands:

    • A command of type tenonRequest.
    • A command of type test with tenon as the value of which.


        "type": "tenonRequest",
        "id": "a",
        "withNewContent": true,
        "what": "Tenon API version 2 test request"

    followed by

        "type": "test",
        "which": "tenon",
        "id": "a",
        "what": "Tenon API version 2 result retrieval"

    The reason for this is that the Tenon API operates asynchronously. You ask it to perform a test, and it puts your request into a queue. To learn whether Tenon has completed your test, you make a status request. You can continue making status requests until Tenon replies that your test has been completed. Then you submit a request for the test result, and Tenon replies with the result. (As of May 2022, status requests were observed to misreport still-running tests as completed. The tenon test works around that by requesting only the result and using the response to determine whether the tests have been completed.)

    Tenon says that tests are typically completed in 3 to 6 seconds but that the latency can be longer, depending on demand.

    Therefore, you can include a tenonRequest command early in your script, and a tenon test command late in your script. Tenon will move your request through its queue while Testaro is processing your script. When Testaro reaches your tenon test command, Tenon will most likely have completed your test. If not, the tenon test will wait and then make a second request before giving up.

    Thus, a tenon test actually does not perform any test; it merely collects the result. The page that was active when the tenonRequest command was performed is the one that Tenon tests.

    In case you want to perform more than one tenon test with the same script, you can do so. Just give each pair of commands a distinct id property, so each tenon test command will request the correct result.

    Tenon recommends giving it a public URL rather than giving it the content of a page, if possible. So, it is best to give the withNewContent property of the tenonRequest command the value true, unless the page is not public.


    The continuum test makes use of the files in the continuum directory. The test inserts the contents of all three files into the page as scripts and then uses them to perform the tests of the Continuum package.

    HTML CodeSniffer

    The htmlcs test makes use of thehtmlcs/HTMLCS.js file. That file was created, and can be recreated if necessary, as follows:

    1. Clone the (HTML CodeSniffer package)[].
    2. Make that package’s directory the active directory.
    3. Install the HTML CodeSniffer dependencies by executing npm install.
    4. Build the HTML CodeSniffer auditor by executing grunt build.
    5. Copy the build/HTMLCS.js and build/licence.txt files into the htmlcs directory of Testaro.
    6. Edit the Testaro copy of htmlcs/HTMLCS.js to produce the changes shown below.

    The changes in htmlcs/HTMLCS.js are:

    >     '4_1_2_attribute': 'attribute',
    >     var messageStrings = new Set();
    <         console.log('done');
    <         console.log('done');
    >       return Array.from(messageStrings);
    <       console.log('[HTMLCS] ' + typeName + '|' + msg.code + '|' + nodeName + '|' + elementId + '|' + msg.msg + '|' + html);
    >       messageStrings.add(
    >         typeName + '|' + msg.code + '|' + nodeName + '|' + elementId + '|' + msg.msg + '|' + html
    >       );
    BBC Accessibility Standards Checker

    The BBC Accessibility Standards Checker has obsolete dependencies with security vulnerabilities. Therefore, it is not used as a dependency of Testaro. Instead, 6 of its tests are reimplemented, in some case with revisions, as Testaro tests. They are drawn from the 18 automated tests of the Checker. The other 12 tests were found too duplicative of other tests to justify reimplementation.


    An example of a branching command is:

      "type": "next",
      "if": ["totals.invalid", ">", 0],
      "jump": -4,
      "what": "redo search if any invalid elements"

    This command checks the result of the previous act to determine whether its result.totals.invalid property has a positive value. If so, it changes the next command to be performed, specifying the command 4 commands before this one.

    A next-type command can use a next property instead of a jump property. The value of the next property is a command name. It tells Testaro to continue performing commands starting with the command having that value as the value of its name property.

    Commands file


    The commands.js file contains rules governing commands. The rules determine whether a command is valid.

    Rule format

    The rules in commands.js are organized into two objects, etc and tests. The etc object contains rules for commands of all types. The tests object contains additional rules that apply to some commands of type test, depending on the values of their which properties, namely which tests they perform.

    Here is an example of a command:

      "type": "link",
      "which": "warming",
      "what": "article on climate change"

    And here is the applicable property of the etc object in commmands.js:

    link: [
      'Click a link',
        which: [true, 'string', 'hasLength', 'substring of the link text'],
        what: [false, 'string', 'hasLength', 'comment']

    The rule is an array with two elements: a string ('Click a link') describing the command and an object containing requirements for any command of type link.

    The requirement which: [true, 'string', 'hasLength', 'substring of the link text'] specifies what is required for the which property of a link-type command. The requirement is an array.

    In most cases, the array has length 4:

      1. Is the property (here which) required (true or false)? The value true here means that every link-type command must contain a which property.
      1. What format must the property value have ('string', 'array', 'boolean', or 'number')?
      1. What other validity criterion applies (if any)? (Empty string if none.) The hasLength criterion means that the string must be at least 1 character long.
      1. Description of the property. Here, the value of which is some substring of the text content of the link that is to be clicked. Thus, a link command tells Testaro to find the first link whose text content has this substring and click it.

    The validity criterion named in item 2 may be any of these:

    • 'hasLength': is not a blank string
    • 'isURL': is a string starting with http, https, or file, then ://, then ending with 1 or more non-whitespace characters
    • 'isBrowserType': is 'chromium', 'firefox', or 'webkit'
    • 'isFocusable': is 'a', 'button', 'input', 'select', or 'option'
    • 'isState': is 'loaded' or 'idle'
    • 'isTest': is the name of a test
    • 'isWaitable': is 'url', 'title', or 'body'
    • 'areStrings': is an array of strings

    When commands.js specifies a withItems requirement for a test-type command, that requirement is an array of length 2, and is always [true, 'boolean']. That means that this test-type command must have a withItems property, whose value must be true or false. That property tells Testaro whether to itemize the results of that test.

    Any test command can also (in addition to the requirements in commands.js) contain an expect requirement. If it does, that requirement has a different format: an array of any non-0 length. The items in that array specify expectations about the results of the test.

    For example, a test command might have this expect property:

    "expect": [
      ["total.links", "=", 5],
      ["total.links.underlined", "<", 6],
      ["docLang", "!", "es-ES]

    That would state the expectation that the result property of the acts item for that test in the report will have a total.links property with the value 5, a total.links.underlined property with a value less than 6, no total.links.outlined property, and a docLang property with a value different from es-ES.

    The second item in each array, if there are 3 items in the array, is an operator, drawn from:

    • <: less than
    • =: equal to
    • >: greater than
    • !: unequal to

    A typical use for an expect property is checking the correctness of a Testaro test. Thus, the validation scripts in the validation/tests/scripts directory all contain test commands with expect properties. See the “Validation” section below.


    You may wish to have Testaro perform the same sequence of tests on multiple web pages. In that case, you can create a batch, with the following structure:

      what: "Web leaders",
      hosts: {
        id: "w3c",
        which: "",
        what: "W3C"
        id: "wikimedia",
        which: "",
        what: "Wikimedia"

    With a batch, you can execute a single statement to run a script multiple times, one per host. On each call, Testaro takes one of the hosts in the batch and substitutes it for each host specified in a url command of the script. The result is a host script. Testaro sequentially runs all of those host scripts.

    Therefore, you cannot use a batch with a script that changes URLs.


    The samples directory contains examples of scripts and batches. If you wish to use them in their current locations, you can give SCRIPTDIR the value 'samples/scripts' and BATCHDIR the value 'samples/batches'. Then execute node high sss to run the sss script alone or node high sss bbb to run the sss script with the bbb batch (e.g., node create simple weborgs). The high module will create a job, run the script or host scripts, and save the report(s) in the directory that you have specified with the REPORTDIR environment variable.



    There are three methods for using Testaro.


    A module in this package can invoke Testaro with this pattern:

    const report = {
      script: {},
      log: [],
      acts: []
    const {handleRequest} = require('./run');
    .then(() => );

    Replace {…} with a script object, like the example script shown above. The low-level method does not allow the use of batches.

    The argument of require is a path relative to the directory of the module in which this code appears. If the module is in a subdirectory, ./run will need to be revised. In an executor within validation/executors, it must be revised to ../../run.

    Another Node.js package that has Testaro as a dependency can execute the same statements, except changing './run' to 'testaro/run'.

    Testaro will run the script and modify the properties of the report object. When Testaro finishes, the log, acts, and other properties of report will contain the results. The final statement can further process the report object as desired in the then callback.


    Make sure that you have defined these environment variables, with absolute or relative paths to directories as their values:


    Relative paths must be relative to the Testaro project directory. For example, if the script directory is scripts in a testing directory that is a sibling of the Testaro directory, then a relative-path SCRIPTDIR must have the value ../testing/scripts.

    Also ensure that Testaro can read all those directories and write to REPORTDIR.

    Place a script into SCRIPTDIR and, optionally, a batch into BATCHDIR. Each should be named with a .json extension., where idvalue is replaced with the value of its id property. That value must consist of only lower-case ASCII letters and digits.

    Then execute the statement node high scriptID or node high scriptID batchID, replacing scriptID and batchID with the id values of the script and the batch, respectively.

    The high module will call the runJob function of the create module, which in turn will call the handleRequest function of the run module. The results will be saved in report files in the REPORTDIR directory.

    If there is no batch, the report file will be named with a unique timestamp, suffixed with a .json extension. If there is a batch, then the base of each report file’s name will be the same timestamp, suffixed with -hostid, where hostid is the value of the id property of the host object in the batch file. For example, if you execute node create script01 wikis, you might get these report files deposited into REPORTDIR:

    • enp46j-wikipedia.json
    • enp45j-wiktionary.json
    • enp45j-wikidata.json


    In watch mode, Testaro periodically checks for a job to be run by it, containing a script and, optionally, a batch. When such a job exists, Testaro runs the script, or uses the batch to create a set of host scripts and sequentially runs them. After running the script or each host script, Testaro converts the report to JSON and disposes of it as specified.

    Testaro checks periodically. The interval between checks, in seconds, is specified by an INTERVAL environment variable.

    After Testaro starts watching, its behavior depends on the environment variable WATCH_FOREVER. If its value is true, watching continues indefinitely. If its value is false or it has no value, watching stops after the first job is found and run.

    To make Testaro start watching, execute the statement node watch.

    There are two ways for Testaro to watch for jobs.

    Directory watch

    With directory watch, Testaro checks whether a particular directory in its host’s filesystem contains a job file. A job file is a JSON-format file named abc.json representing an object like this:

      "script": {},
      "batch": {}

    The batch property is optional. The value abc may be replaced with any string of lower-case ASCII letters and digits.

    When Testaro finds job files in the directory, Testaro runs the first job, writes the report(s) into the report directory, and moves the job file into the ex-jobs directory.

    Testaro suspends checking while it is running any job. Therefore, even though the currently running job file remains in JOBDIR, Testaro will not try to run it again.

    Since Testaro runs the first job (i.e. the job whose name is first in ASCII order), whoever populates the directory with job files has control over the order in which Testaro runs them. For example, to force a new job to be run before the already waiting jobs, one can give it a filename that comes before that of the first waiting job.

    In order to make directory watching possible, you must define these environment variables:

    • WATCH_TYPE=dir
    • WATCH_FOREVER (=true or =false)
    • JOBDIR
    Network watch

    With network watch, Testaro asks a particular API whether it has any jobs for the current instance of Testaro, identified by an authorization code. If the response is a JSON representation of an object satisfying the same requirements as given above under “Directory watch”, Testaro runs the job and sends the report(s) to the API.

    Thus, if there are multiple jobs queued for the Testaro instance, the API is responsible for choosing one of them to send in response.

    When the API receives the reports, it can dispose of them as desired. Each report is a JSON representation of an object, which has these identification properties:

    • jobID
    • timeStamp
    • id

    The jobID property can be used for an association between each report and the job that it arose from. The timeStamp property can be used for an association of all the reports in a batched job. And the id property (which begins with the time stamp) is unique to each report.

    In order to make network watching possible, you must define these environment variables:

    • WATCH_TYPE=net
    • WATCH_FOREVER (=true or =false)
    • PROTOCOL (=http or =https)
    • JOB_URL (not including the authorization code)
    • REPORT_URL (not including the authorization code)

    Environment variables

    As mentioned above, using the high-level method to run Testaro jobs requires SCRIPTDIR, BATCHDIR, and REPORTDIR environment variables.

    If a tenon test is included in the script, environment variables named TENON_USER and TENON_PASSWORD must exist, with your Tenon username and password, respectively, as their values.

    If a wave test is included in the script, an environment variable named WAVE_KEY must exist, with your WAVE API key as its value.

    The text command can interpolate the value of an environment variable into text that it enters on a page, as documented in the commands.js file.

    Before executing a Testaro script, you can optionally also set the environment variables DEBUG (to 'true' or anything else) and/or WAITS (to a non-negative integer). The effects of these variables are described in the index.js file.

    You may store these environment variables in an untracked .env file if you wish, and Testaro will recognize them.



    Testaro and its custom tests can be validated with the executors located in the validation/executors directory.

    The executors are:

    • low: validates low-level invocation
    • high1: validates high-level invocation of a script without a batch
    • high2: validates high-level invocation of a script with a batch
    • watchDir: validates directory watching
    • watchNet: validates network watching
    • tests: validates all the custom tests (not the test packages)

    To execute any executor xyz, call it with the statement node validation/executors/xyz.

    The tests executor makes use of the scripts in the validation/tests/scripts directory, and they, in turn, run tests on HTML files in the validation/tests/targets directory.


    You can define additional Testaro commands and functionality. Contributions are welcome.

    Please report any issues, including feature requests, at the repository.

    Accessibility principles

    The rationales motivating the Testaro-defined tests can be found in comments within the files of those tests, in the tests directory. Unavoidably, each test is opinionated. Testaro itself, however, can accommodate other tests representing different opinions. Testaro is intended to be neutral with respect to questions such as the criteria for accessibility, the severities of accessibility issues, whether accessibility is binary or graded, and the distinction between usability and accessibility.

    Testing challenges

    Abnormal termination

    On rare occasions a test throws an error that terminates the Node process and cannot be handled with a try-catch structure. It has been observed, for example, that the ibm test does this when run on the host at or

    If a single process performed all of the commands in a batch-based script, the process could perform tens of thousands of commands, and such an error could stop the process at any point.

    To handle this risk, Testaro processes batch-based jobs by forking a new process for each host. If such an error occurs, it crashes the child process, preventing a report for that host from being written. The parent process waits for the report to appear in the REPORTDIR directory until the time limit. When it fails to appear, the parent process continues to the next host.

    If you are using high-level invocation, your terminal will show the standard output of the parent process and, if there is a batch, the current child process, too. If you interrupt the process with CTRL-c, you will send a SIGINT signal to the parent process, which will handle it by sending a message to the child process telling it to terminate itself, and then the parent process will terminate by skipping the remaining hosts.


    Testing to determine what happens when a control or link is activated is straightforward, except in the context of a comprehensive set of tests of a single page. There, activating a control or link can change the page or navigate away from it, interfering with the remaining planned tests of the page.

    The Playwright “Receives Events” actionability check does not check whether an event is dispatched on an element. It checks only whether a click on the location of the element makes the element the target of that click, rather than some other element occupying the same location.

    Test-package duplication

    Test packages sometimes do redundant testing, in that two or more packages test for the same issues, although such duplications are not necessarily perfect. This fact creates three problems:

    • One cannot be confident in excluding some tests of some packages on the assumption that they perfectly duplicate tests of other packages.
    • The Testaro report from a script documents each package’s results separately, so a single difect may be documented in multiple locations within the report, making the consumption of the report inefficient.
    • An effort to aggregate the results into a single score may distort the scores by inflating the weights of defects that happen to be discovered by multiple packages.

    The tests provided with Testaro do not exclude any apparently duplicative tests from packages.

    To deal with the above problems, you can:

    • revise package test commands to exclude tests that you consider duplicative
    • create derivative reports that organize results by defect types rather than by package
    • take duplication into account when defining scoring rules

    Some measures of these kinds are included in the scoring and reporting features of the Testilo package.

    Repository exclusions

    The files in the temp directory are presumed ephemeral and are not tracked by git.

    Related packages

    Testilo is an application that:

    • produces scores and adds them to the JSON report files of Testaro
    • produces human-oriented HTML digests from scored reports
    • produces human-oriented HTML reports comparing the scores of hosts

    Testaro is derived from Autotest.

    Testaro omits some functionalities of Autotest, such as:

    • tests producing results intended to be human-inspected
    • scoring (performed now by Testilo)
    • file operations for score aggregation, report revision, and HTML reports
    • a web user interface

    Code style

    The JavaScript code in this project generally conforms to the ESLint configuration file .eslintrc. However, the htmlcs/HTMLCS.js file implements an older version of JavaScript. Its style is regulated by the htmlcs/.eslintrc.json file.


    Work on the custom tests in this package began in 2017, and work on the multi-package federation that Testaro implements began in early 2018. These two aspects were combined into the Autotest package in early 2021 and into the more single-purpose packages, Testaro and Testilo, in January 2022.


    “Testaro” means “collection of tests” in Esperanto.


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