Have Diffblue Cover write unit tests for your public Java repo for free

Provide us a public repo url (e.g. Github, Gitlab, Bitbucket) and we’ll submit a PR/MR for your review


We will process your personal data in accordance with our Privacy Notice


How does it work?

1Use this page to submit your public Java repo for review

Submit your Java repo

2Diffblue Cover will analyze your repo and generate unit tests

Repo analysed by Diffblue Cover

3We will create a pull request so you can commit the generated tests

Pull request generated

4Merge the pull request, add the Diffblue Cover tests to your repo and improve your test coverage

Pull request merged

Interested in Diffblue Cover?

Recently merged open source pull requests

Click on a logo below to view the GitHub commit

Frequently Asked Questions (FAQs) on Open Source PRs

What are the benefits of merging a PR containing Diffblue unit tests

The obvious benefit to repo owners is free tests(!) which saves time for contributors to spend on developing code. Diffblue gains from any feedback received to help us continue to improve the tool.

Why is Diffblue submitting PRs to Open Source repositories?

Diffblue has a history of involvement in the Open Source community and is committed to providing unit tests to public repositories without obligation. We’ve also found this to be an effective way to continually test our product against diverse code bases.

Does this commit me to using Diffblue Cover in the future?

No. Once the unit tests are merged into a repository they become part of it and can be used independently.

Will the tests find bugs in my code?

The tests are not designed to find bugs but represent the exact behaviour of the code right now and so should always pass. If a test fails, it probably means that the underlying code has changed. This can then be investigated by project contributors to see if the change is expected (perhaps as a result of an enhancement) or unexpected, in which case action can be taken to restore the code to its previous functional state. Many times the review of a Diffblue Cover test by someone familiar with the underlying source has shown that the code is not implemented exactly as intended, which has led to the repo owner fixing that bug.

How do we maintain Diffblue unit tests in the future?

Diffblue unit tests are like any other unit tests and can be maintained in the same way. Once integrated into a code base, they can be updated, reworked or deleted as necessary.

Can I modify the tests once integrated into my project?

Yes, the tests become part of the project once merged and so can be changed to suit, like any other source file.

How does Diffblue cover handle external services e.g. databases?

Diffblue Cover uses mocking frameworks such as Mockito and Powermock.

Is it possible to receive more unit tests?

Yes. If an initial PR is merged, further PRs may be submitted to provide tests for other classes as discussed with repository owners. Feel free to also submit more repositories on the form at the top of the page.

Is there a free version of Diffblue Cover that I can try?

There is not a free full version of the product yet, but a feature-limited version is available called Diffblue Playground free of charge. A simple sign-up is required to create tests for a single class - either one of the samples or your own, typed or pasted in.

Who is Diffblue?

Diffblue is a software company whose mission is to make software developers and their teams wildly more successful. For more information visit our About Us page.

What is Diffblue Cover?

Diffblue Cover is a program that writes unit tests for Java code bases. To learn more, please see our one-page datasheet or check out our product page for details and videos.

Have a question that wasn’t answered above?

You can ask any further questions on our Contact Us page.