What's New > Version 2021.07.01

Getting the best from Diffblue Cover

Release date: Jul 06, 2021

Getting the best unit testing experience from Diffblue Cover

For both our IntelliJ plugin and our CLI, we have enabled environmental checks to ensure you have the best combination of environmental dependencies (and can therefore write great tests!):

  • We check that you have either Java 8 or 11 (but not 11.0.7, which is buggy)
  • We check that there isn’t a mismatch between the version of Java you are using and the version used for compilation.

For the CLI only:

  • We also check that you have supported versions of Maven (3.6.1+) and Gradle (2.6+).

We have also expanded our feedback messaging to help developers understand how more tests can be created, and to guide you in using Diffblue Cover. This feedback messaging gives information directly, and also links to the documentation on our website for more details.

Recent blog posts

Have you seen our recent blog posts? Catch up with the new testability information in our IntelliJ plugin, and also (for our Enterprise customers) see how to unlock coverage gaps using Diffblue Cover CLI’s new coverage reports:

Diffblue Cover Community Edition is available for use with commercial code

Community Edition allows you to write tests for both open source and commercial code. This means you can now use Diffblue Cover Community Edition at work completely for free. Visit our documentation to learn more about how you can use Diffblue Cover at work, and also see our End-User License Agreement.


If you have feedback, questions or requests regarding the Diffblue Cover IntelliJ Plugin, please contact us on the Community Forum. We would love to hear about what is important to you and what you would like to see in upcoming releases.

How do I automatically maintain all of these tests?

Use Diffblue Cover on any CI platform to automatically update your unit tests and catch regressions for every commit - watch this video to learn more.

Full Release Notes


  • Cover can now write tests with longer Arrange sections, if required. [Ref: TG-14865]

  • Cover now exits with an error if an unsupported version of Java is being used, or, if there is a mismatch between the version of Java being used and the version used for compilation. [Ref: TG-14763]

  • Cover now provides improved output and further guidance if the ‘inotify limit’ is reached. [Ref: TG-14740]

  • Cover now writes tests which fully initialize POJOs in the Arrange section by calling their setters. [Ref: TG-14685]

  • Cover now provides improved output code reporting and further guidance for R002, R003, R004, R007, R010 and R011. [Ref: TG-14513]

  • Cover now supports @Value in Spring Framework projects. [Ref: TG-14353]

  • CLI: Cover now provides warnings if key test framework components are missing from the classpath. [Ref: TG-14765]

  • CLI: Cover now exits with an error if an unsupported version of Maven or Gradle is being used. [Ref: TG-14764]

Resolved Issues

  • CLI: Resolved an issue which would cause Cover to terminate with Command could not be completed due to an unexpected error: null if dcover create is executed in a project without Java code. [Ref: TG-14870]

  • CLI: Resolved an issue where, in some circumstances, when test validation fails, Cover may remove all tests it has written. [Ref: TG-14745]

  • IntelliJ Plugin: Resolved an issue which prevented ‘Write Tests’ from writing tests on a default package and ancestor project directories. [Ref: TG-14828]

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, whilst using Cover’s ‘write test’ flask icon, provoked an IntelliJ IDEA IndexNotReadyException error report. [Ref: TG-14799]

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, may cause tests to be written to a non-java test directory in multi-language projects. [Ref: TG-14715]

Known Issues

  • CLI: dcover clean --failing fails when used with a Gradle project. [Ref: TG-11707]

  • IntelliJ Plugin: Diffblue Cover was unable to create an index error may appear if switching project happens before Cover has finished indexing. [Ref: TG-13772]