Diffblue Cover Enhancements

Skeleton tests are now available in Diffblue Cover IntelliJ plugin! There are two ways of creating skeleton tests:

  • Indirectly, via the usual “Write Tests” request. Diffblue Cover analyses the method and related classes to write tests. If Diffblue Cover is unable to write complete tests (or partial tests if this option is enabled), it falls back to offering a single skeleton test for the method instead. This means that Diffblue Cover always creates at least one test for each of your methods.

For further information, and an example of a skeleton test, please see our documentation at: https://docs.diffblue.com/knowledge-base/intellij/skeleton-tests/

This release, we also:

  • Provide additional information when a class fails to load due to a static initialization failure

  • No longer create tests for default constructors in utility classes, thus avoiding the situation where there are no fields that could be asserted on.

Developer Edition trial available

We are delighted to now offer a 14-day trial version of our Developer Edition, which includes the Diffblue Cover CLI, as part of our new licensing option. We're really excited that you can now "try before you buy"! To download your trial of Diffblue Cover Developer Edition, please click here. Full information on all our options is also available here.

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.


  • CLI: Cover's installer now removes previous installation entries whilst upgrading to a newer version. [Ref: TG-17155]

  • Cover now has improved output code reporting, correctly identifying more R006s (Static initializer failed), some of which which were previously reported as R005 (Unable to load class). [Ref: TG-17097]

  • CLI: Cover now provides a coverage-reports option to allow coverage reports to be generated without writing tests. [Ref: TG-17091]

  • Cover now has improved handling of implicit default constructors of static utility classes. [Ref: TG-16609]

Resolved Issues

  • Resolved an issue which caused Cover to report an F009 (Internal Error) with Act steps must be contained in the steps. [Ref: TG-17105]

  • Resolved an issue which, in some circumstances, caused Cover to report an F009 (Internal Error) with NoClassDefFoundError after attempting to temporarily disable logging in the code for which tests were being written. [Ref: TG-17104]

  • Resolved an issue which caused Cover to write tests which assert on loopback and private network IP addresses. [Ref: TG-11594]

  • IntelliJ Plugin: Resolved an issue which, in some circumstances, caused Cover to write @DataJpaTests with missing properties setup. [Ref: TG-17175]

Known Issues

  • CLI: The command dcover clean --failing does not work on Gradle projects. This command is now deprecated and dcover validate should be used instead. [Ref: TG-11707]

  • For multi-module projects, --coverage-reports needs to be run in the sub-modules, not from the root module with --working-directory. [Ref: TG-16876]

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