2025-11-02
This release introduces support for JUnit 6 on Java 17+ and compatibility with IntelliJ 2025.3 EAP. The dcover issues command is also enhanced with a more scannable output and paging, and overall CLI memory usage is reduced.
Framework & IDE Support
JUnit 6 Support: Diffblue Cover now writes tests compatible with JUnit 6 for projects using Java 17 and higher. For projects on Java versions 8 through 16, Cover continues to generate tests using the JUnit 5 framework.
IntelliJ 2025.3 EAP Compatibility: The Diffblue Cover IntelliJ plugin is now compatible with the IntelliJ 2025.3 Early Access Program (EAP), ensuring seamless test generation in the newest pre-release IDE versions.
Command-Line Interface (CLI) Enhancements
dcover issuesUsability: Thedcover issuescommand is now more scannable, using bold headings and method counts for a compact view. The command also supports paging via a new--skipoption, which can be combined with--limitto navigate the issue list. The--detailsoption has been removed; use--promptsfor detailed information.Reduced Memory Usage: Cover now uses less memory when writing tests via the CLI. The memory footprint remains stable throughout test generation, improving performance and stability for large projects.
Cleaner Console Output: Resolved an issue that caused unnecessary console messages about synthetic or generated methods, resulting in a less verbose output from the CLI.
Enterprise Reporting
Usage Tracking in Cover Reports: For enterprise deployments, Cover Reports can now track command line and plugin usage. Enable this feature by setting the
telemetry.collect.usernameproperty in thetelemetry.propertiesfile to record the user's git identity.
Stability & Security
Enhanced Sandbox Security: Resolved a rare issue where file writes could escape the sandbox during test generation on Java 8 through 24, enhancing the stability and security of the test generation process.
Important Notices
Upcoming Change to Test Generation
From release 2025.12.01, Cover will optimize its test output to provide the same level of Diffblue Coverage by removing tests that provide redundant coverage within the same test class. This means Cover will produce fewer tests while maintaining the same level of Diffblue Coverage, reducing code bloat and maintenance overhead. This feature will be enabled by default.
In addition, a new CLI option, --ignore-existing-coverage, will be introduced. You can use this option to disable the new behavior for a single run.
Upcoming End of Support for IntelliJ 2025.1
This release is the final release that supports IntelliJ 2025.1. In line with our policy of supporting the two most recent major versions, support for 2025.1 will be discontinued in an upcoming release.
To continue receiving Diffblue Cover updates and support, users on IntelliJ 2025.1 are advised to upgrade to IntelliJ 2025.2 or newer.
Enhancements
Diffblue Cover now supports paging for the
dcover issuescommand. A new--skipoption has been added, which can be combined with the existing--limitoption to display a specific 'page' of the prioritized issue list. [Ref: TG-23962]CLI: Diffblue Cover now provides a more scannable
dcover issuesoutput. Bold headings and method counts replace full method lists for a compact view. The--detailsoption is removed; use--promptsfor detailed information and LLM-ready prompts. [Ref: TG-23917]For enterprise deployments, Cover Reports can now track command line and plugin usage. Enable this feature by setting the
telemetry.collect.usernameproperty in thetelemetry.propertiesfile to record the user's git identity. [Ref: TG-23916]Diffblue Cover now writes tests compatible with JUnit 6 for projects using Java 17 and higher. For projects on Java versions 8 through 16, Diffblue Cover continues to generate tests using the JUnit 5 framework. [Ref: TG-23826]
CLI: Diffblue Cover now uses less memory when writing tests. The memory footprint remains stable throughout the test generation process, regardless of run duration or the number of tests created, improving performance and stability for large projects. [Ref: TG-23717]
Plugin: The Diffblue Cover IntelliJ plugin is now compatible with the IntelliJ 2025.3 Early Access Program (EAP), allowing unit test generation within the newest pre-release versions of the IDE. [Ref: TG-22571]
Resolved Issues
CLI: Resolved an issue that caused unnecessary console messages about synthetic or generated methods. The output from Diffblue Cover is now less verbose, no longer including entries for methods that are not candidates for test creation. [Ref: TG-23936]
Resolved an issue where, in rare cases, file writes could escape the sandbox during test generation on Java 8 to Java 24. This enhances the overall stability and security of the test generation process. [Ref: TG-23909]
Known Issues
Plugin: Diffblue Cover incorrectly displays a menu option to write tests for existing test files. [Ref: TG-17163]
Using JDKs other than the supported Open JDK and Oracle JDK may produce unexpected results due to implementation differences. [Ref: TG-19345]
Cover may encounter an
F009(Internal error) caused by aClassCircularityErrorinvolvingorg/mockito/configuration/MockitoConfigurationwhen writing tests with Mockito 5. The recommended workaround is to downgrade to Mockito 4.x. [Ref: TG-19610]Reports: The total line count metric in Reports only includes Java code. Kotlin code is not included. [Ref: TG-22088]
Reports: Total lines of code metric can incorrectly count a multi-line comment at the end of a line of code, resulting in fewer than expected lines counted. [Ref: TG-22089]
Reports: Following an upgrade, the 'Total Lines of Code' card may show 0 until a new reports bundle has been uploaded. [Ref: TG-22094]
Cover may write more simplistic tests with less meaningful assertions when Spring Boot dependency injection is disabled. [Ref: TG-22102]
In some circumstances, Cover will still write Spring Boot tests when Spring Boot dependency injection is disabled. [Ref: TG-22103]
Cover may write failing TestNG tests when Spring Boot dependency injection is disabled. [Ref: TG-22107]
Plugin: On some displays, the Test Review subsection title 'Tests for review' is malformed. [Ref: TG-22805]
When test formatting settings are changed, the Test Review feature may incorrectly remove the
@ManagedByDiffblueannotation from tests, particularly in cases involving static import formatting changes. [Ref: TG-23750]Plugin: Using the Test Review feature may create tests that have incompatible dependency injection systems. [Ref: TG-23935]
Cover: If Dependency Injection libraries change between runs, Cover may select the DI system from a previously-generated test instead of a more suitable DI system now available on the classpath. [Ref: TG-24021]
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