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retest / recheck-web

recheck for web apps – change comparison tool with local Golden Masters, Git-like ignore syntax and ...

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recheck-web is a Golden Master-based test framework on top of Selenium that allows for easy creation and maintenance of more complete and nearly unbreakable tests. If you want to give it a quick try, checkout the Chrome extension that is based on recheck-web.


Imagine you could:

  1. Have your end-to-end tests actually fail when the website is broken or unusable (including visual regressions)
  2. Have your tests NOT fail when something as insignificant as an element ID changes
  3. Maintain your tests with minimal effort

recheck-web gives you these superpowers, and more.

Table of Contents


A typical Selenium test could look like the following:

driver.findElement( "username" ) ).sendKeys( "Simon" );
driver.findElement( "password" ) ).sendKeys( "secret" );
driver.findElement( "sign-in" ) ).click();

assertEquals( driver.findElement( By.tagName( "h4" ) ).getText(), "Success!" );

If the website e.g. loses all of its CSS, thus rendering it essentially broken for a user, this test will still pass. However, if you change an invisible attribute that is irrelevant for a user, e.g. the element ID

, this test will break.

By simply wrapping the driver in a

and adding either a call to
or our JUnit 4 or JUnit 5 extension, all of this changes. When the looks of the website change, the test will fail. And if the element ID changes, the test will still execute, albeit report the change—unless you chose to ignore it e.g. by specifying
in your
file (a file similar to Git's


With recheck-web you can: * Easily create and maintain checks in your tests * Perform deep visual testing that goes beyond the UI and doesn't fail with every shifted pixel, i.e. semantically compare all of the contents, tags and CSS attributes of websites or

s after rendering * Easily ignore volatile elements, attributes or sections, using a Git-like syntax * Automatically maintain Golden Masters (and soon auto-heal your tests) with intended changes, using our GUI or CLI * Be sure no unexpected change goes unnoticed * Reuse your existing tests and infrastructure, as recheck-web operates on top of Selenium and is compatible with many test frameworks * Use a virtual constant
to reference elements, instead of element IDs, names, XPaths and other attributes that are prone to changes * Have virtually unbreakable Selenium tests

How It Works

Automated regression tests are not tests, in the sense that they don't aim to find existing bugs. Instead, they guard against unintended changes. As such, they are an extension to version control—but today's test tools are not optimized for this work flow.

recheck takes this to the next level. You can explicitly or implicitly create Golden Masters (essentially a copy of the rendered website) and semantically compare against these. Irrelevant changes are easy to ignore and the Golden Masters are effortless to update. In case of critical changes that would otherwise break your tests, recheck-web can now peek into the Golden Master, find the element there, and (based on additional attributes) still identify the changed element on the current website.

best-match copy


If you just want to quickly try recheck-web without the hassle of a full-project setup, we recommend using the Chrome extension that is based on recheck-web.

recheck-web operates on top of Selenium. Selenium has become an official W3C standard, supported by all major browsers. Learn more about Selenium and how to install it.

Simply add

as dependency to your project, e.g. via Maven Central: Latest recheck-web on Maven Central

recheck-web leverages recheck, which is available as a Java API with support for JUnit 4 and JUnit 5 as well as TestNG.

Now either create explicit checks or implicit checks.

Explicit Checks

For explicit checks in your tests:

  • Create an instance of
    , e.g. via
    Recheck re = new RecheckImpl()
    (typically in your
  • Start tests via
  • Check the complete current website via
    re.check(driver, "check-name")
    or individual web elements via
    re.check(webElement, "check-name")
  • Make the test fail on changes via
  • Produce a
    file via
    (e.g. in your
    ), so changes can easily be applied to the Golden Masters

A simple example test with explicit checks can be found in the SimpleRecheckShowcaseIT.

A complete tutorial about how to setup and use recheck-web like this can e.g. be found in our documentation.

Implicit Checks

You can also use the recheck driver wrapper, which will automatically create a check after every action. To use this, simply wrap your driver like so:

driver = new RecheckDriver( new ChromeDriver() );

Then you either need to call

after your test has finished, or you can integrate recheck into your JUnit life-cycle with our JUnit 4 and JUnit 5 extensions.


If there are any questions that are not answered here, please do not hesitate to ask!

Why does my test fail the first time?

Running a recheck-web test for the first time will result in a failure with an output like so:

java.lang.AssertionError: No Golden Master found. First time test was run? Created new Golden Master, so don't forget to commit...
    at de.retest.recheck.RecheckImpl.capTest(

Running such a test will also create a folder structure containing a

file and a screenshot per check, the location of both depends on your configuration, see below. This contains the Golden Master against which future executions of this test are compared. If you use version control, you should commit those files. Note that the
contains a full description of the rendered website, including all relevant information such as text, source, etc. and all non-default CSS attributes such as font and margin. Although these files may become large, they are smaller than the original and by ignoring specific (or all) attributes, you can configure how large they are. Anyways, storing a few kilobyte extra is much cheaper than the manpower needed to manually specify such checks.

Executing the same test again should not result in any differences. But after changing the website and executing the test, you should see the test reporting your changes.

Help, I have too many changes! What do I do?

You need to decide what the goal of your test setup is. With traditional assertions, you ignore more than 99% of the changes. Instead, much like Git without an ignore file, recheck-web will report every change. So it is up to you to ignore changes that are not of interest for you. recheck-web can be used for cross-browser and cross-device testing, deep visual regression testing and functional regression testing. recheck-web is just a tool, it depends on you how you want to use it.

A good starting point are the pre-defined filter files in recheck. Ignoring positioning is usually a good idea. If you want to know more about the ways to maintain your ignore file or create your own filters, refer to the detailed documentation.

If you didn't change anything between two executions, you can use our CLI and e.g. call

recheck ignore --all
to simply add all changes as ignore rules to your

I still have too many changes! What do I do?

You can use filters in conjunction with the CLI or the GUI to quickly drill down on what changes are relevant to you. E.g. ignore changes to positioning, CSS and invisible attributes, and see only changes in content using:

recheck diff --exclude positioning.filter \
        --exclude style-attributes.filter \
        --exclude invisible-attributes.filter \

If you have trouble with this, please contact us, so we can learn on how to improve this for you.

How can I configure the location of the Golden Master files?

You can provide a project layout via the

RecheckOptions opts = RecheckOptions.builder()
        .projectLayout( new CustomProjectLayout() )
driver = new RecheckDriver( new ChromeDriver(), opts );

The default project layout is Maven and will create Golden Master files under

and reports as
in your
folder. A Gradle layout is also available. If you want your Golden Master files and reports to be located somewhere different, implementing this interface is straightforward.

The naming strategy is responsible for automagically retrieving names for the suite and test. The default implementation does so based on the JUnit names. An explicit naming strategy with setters and getters is also available.

How can I open the

You can open the

using review or the open-source recheck.cli. Both let you easily accept changes with a single click (patent pending) or a single command. This also saves a lot of time during maintenance. Moreover, any regularly changing aspect or element (e.g. date fields) can easily be ignored (see above).

recheck-web seems to be slow when executing. What can I do about that?

recheck-web itself is not slow. But screenshot creation is. Lucky enough, we only use the screenshot for documentation, not for the actual comparison. Per default, we only create a screenshot of the given viewport and scale that to a max width. You can also disable the screenshot creation completely. For more information, please refer to our documentation.

What does the recheck warning mean?

recheck-web can identify elements even after the identifying attribute has changed. So assume you are using, e.g. an HTML

property to identify an element within your Selenium test. Now, assume that this
property changes within the HTML. With traditional Selenium, your test would break, resulting in a
. But using e.g. the
as a drop-in replacement/wrapper of your normal driver, recheck-web magically finds the element and logs a warning such as:
*************** recheck warning ***************
The HTML id attribute used for element identification changed from 'username' to 'user'.
retest identified the element based on the persisted Golden Master.
If you apply these changes to the Golden Master, your test de.retest.recheck.example.MyUnbreakableSeleniumTest will break.
Use `"user")` or `By.retestId("username")` to update your test

How can I use unbreakable Selenium with explicit calls to check?

In order to use "Unbreakable Selenium", you just need to wrap your usual driver in an

(drop-in replacement) and use
instead of
. The code would look like so):
// Use the RecheckDriver as a wrapper for your usual driver.
driver = new UnbreakableDriver( new ChromeDriver() );
// Use the unbreakable recheck implementation.
re = new RecheckWebImpl();

Note that this works only in conjunction with at least one previous call to

, as behind the scenes, if the element cannot be found on the current page, then recheck-web searches for it in the last Golden Master (where e.g. the ID still is), makes a 1-on-1 assignment to the current elements and returns the element with the highest match, if it's higher than a configurable confidence level. Also check out the other ways of using recheck-web.

Can I use recheck-web on a CI/CD server?

Yes, recheck-web easily integrates into your CI/CD environment. I can even be used with headless Selenium. Have a look at our tests for various examples.

How can I access the report files on my CI/CD server?

If you cannot readily access the reports on your CI/CD server, test reports can be easily uploaded to rehub. To upload reports, you will need a retest account.

The first step is to modify the

method in our existing test case to enable the upload to rehub. There are two ways to achieve this:
  • Set the
    system property (you have to do this before
    is created)
void setUp() {
    System.setProperty( Properties.REHUB_REPORT_UPLOAD_ENABLED, "true" );
    re = new RecheckImpl();
    // ...
  • Or set the rehub flag via
void setUp() {
    RecheckOptions options = RecheckOptions.builder()
    re = new RecheckImpl( options );
    // ...

Of course this can also be done with the

, but then use the
    RecheckWebOptions options = RecheckWebOptions.builder()
    driver = new RecheckDriver( new ChromeDriver(), options );
    // ...

If we execute the test locally and the configuration was successful, your browser will pop up and you will be prompted to login. Afterwards, you can find your test reports on rehub dashboard.

A detailed tutorial can be found in our documentation.


This project is licensed under the AGPL license.

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