What's New > Version 2021.06.01

Updated icons for Diffblue Cover IntelliJ plugin

Release date: Jun 07, 2021

New icons for IntelliJ plugin

The Diffblue Cover IntelliJ plugin has new icons to help you write tests!

Indexing  - we are discovering your project structure! Meanwhile, click on the icon to write tests.

Write tests  - click on the icon to write tests for this method or class.

Untestable  - this method or class cannot be tested; click on the icon to find out why.

Private method  - this method cannot be tested as it is private but it may be tested indirectly via a public method. Please make this method public or package protected if you would like to write unit tests.

Test writing in progress  - please wait while we finish!

For further help:

  • Right clicking on an icon provides a popup menu with further details.
  • Icons show the name of method or class for which they will write tests.
  • When Diffblue Cover is writing tests, all icons are updated to “in progress” and cannot be used to write further tests until the original test writing has finished.
  • Methods can be marked with icons indicating that they are “unit-testable”, “not unit-testable by design” or “can be unit-tested after code changes”.

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


  • IntelliJ Plugin: Cover now only shows a ‘write tests’ flask icon next to methods which are likely to be testable. Methods which are unlikely to be testable by Cover show a different icon which provide guidance on how to make them testable by Cover. [Ref: TG-14399]

  • IntelliJ Plugin: Cover now allows ‘write tests’ flask icons to be clicked whilst Cover is indexing. [Ref: TG-14614]

  • IntelliJ Plugin: Cover now automatically creates IntelliJ IDEA ‘run configurations’ allowing environment variables and system properties, used whilst writing tests, to be configured. [Ref: TG-14253]

  • CLI: Cover now provides improved output, and guidance, when running dcover create on a project which hasn’t already been compiled. [Ref: TG-14317]

  • Cover now writes tests for methods that return a Predicate object. [Ref: TG-13578]

  • Cover now writes tests for projects which use Spring 4. [Ref: TG-14350]

  • Cover now has improved support for Spring projects when ApplicationContext is injected in to beans. [Ref: TG-14476]

  • Cover now has improved support for Spring repository beans. [Ref: TG-14456]

  • Cover now has improved support for equals and hashCode methods. [Ref: TG-11223]

Resolved Issues

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, provoked an E009 error, resulting in a E019 (Failed to create Spring context), whilst attempting to ‘Write tests’. [Ref: TG-14658]

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, provokes a Throwable: Project is already disposed error to be shown. [Ref: TG-14632]

  • Resolved an issue which, in some circumstances, caused redundant Matchers.containsString() Hamcrest matchers to be added to assertions in tests for Spring controllers. [Ref: TG-14576]

  • Resolved an issue which would occur when Cover is unable to write assertions for a test, where an R004 (Unable to find any meaningful assertion) would be shown, rather than a more specific error code. [Ref: TG-14571]

  • Resolved an issue where Cover attempts to use Hibernate-injected methods as setters whilst writing tests, causing Hibernate Managed Entities to appear in projects without Hibernate on the classpath. [Ref: TG-14457]

  • Resolved an issue which, in some circumstances, provoked a java.lang.OutOfMemoryError: GC overhead limit exceeded error whilst writing tests for some recursive methods. [Ref: TG-14193]

Known Issues

  • CLI: Windows: creating config.json by outputting --example-config as file causes exceptions. [Ref: TG-11198]

  • CLI: All tests may be discarded in test validation when using --config. [Ref: TG-11475]

  • CLI: dcover clean --working-directory throws an error if --test-output-dir is not provided. [Ref: TG-11665]

  • 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]