# 2025-06-02 ## 2025-06-02 This release enhances how Diffblue Cover writes tests by adding new mock configuration controls to handle more complex scenarios, and by improving its resilience to project configuration issues. * **Mock Configuration & Control**: * **Mocks:** Cover now provides greater control over generated mocks using new `@InTestsMock` attributes. You can direct Cover to generate mocks that throw specific exceptions (`throwException`) or create custom return values from an object factory (`returnValueFactory`). * **Core Engine & Tooling Stability**: * **Core Engine:** Addressed R005 and F009 errors that could prevent Cover from writing tests in projects with missing parent dependencies or corrupt `.jar` files. * **CLI & Plugin:** Improved stability by resolving a CLI issue with the `--new-jacoco-coverage` command and fixing a performance issue in the IntelliJ plugin that could cause the UI to become unresponsive. ## Important Notices ### Changes to test code * **Test formatting**: In the **2025.06.03** release, Cover will switch the default test formatting style to `google-java-format`. This change will cause a one-time reformatting of existing test files, resulting in larger-than-usual diffs. An alternative formatter configured in your build system will override this new default. * **Test tagging and ownership annotations**: In the **2025.06.03** release, Cover will replace `@Tag("MaintainedByDiffblue")` with the new `@ManagedByDiffblue` and `@Tag("ContributionFromDiffblue")` annotations. This will cause a one-time update to existing Diffblue tests. To take ownership of a test and prevent it from being overwritten, remove its `@ManagedByDiffblue` annotation. * **Action Required for `DiffblueBuild.yaml`**: To ensure correct coverage reporting, users with a `DiffblueBuild.yaml` file from before release `2025.06.02` **must** manually update it. Replace all instances of `"MaintainedByDiffblue"` with `"MaintainedByDiffblue,ContributionFromDiffblue"` and set the file version to `2.1`. ### Deprecations * **Cover Reports authentication properties**: The deprecated `reports.requiredusername` and `reports.requiredpassword` properties (and their corresponding `REPORTS_REQUIREDUSERNAME`/`PASSWORD` environment variables) will be removed in the **2025.06.03** release. Please migrate to the new `reports.users.upload.username` and `reports.users.upload.password` properties (or the `REPORTS_USERS_UPLOAD_USERNAME` and `REPORTS_USERS_UPLOAD_PASSWORD` environment variables) to prevent upload failures after the update. ### Removed Features * **`--existing-coverage` option**: The CLI option `--existing-coverage` for the `dcover create` command has been removed as of this release (2025.06.02). To write tests that target only new coverage, use the `--new-jacoco-coverage` option. ### Enhancements * Diffblue Cover now includes improved error handling for missing dependencies on the classpath. This enhancement prevents test generation from failing when a parent class cannot be found, significantly reducing R005 errors. \[Ref: TG-23232] * Diffblue Cover now offers two ways to configure thrown exceptions from mocks using `@InTestsMock`. Specify an exception directly by its `Class` with the `throwException` attribute, or by a factory method with `throwExceptionFactory`. \[Ref: TG-23051] * Diffblue Cover now allows specifying a factory for creating custom object return values in mocks, using the new `returnValueFactory` field in the `@InTestsMock` annotation. \[Ref: TG-22955] * Plugin: Diffblue Cover can now be installed on IntelliJ IDEA Community Edition 2025.2 EAP and IntelliJ IDEA Ultimate 2025.2 EAP. This support is currently in preview mode. \[Ref: TG-22566] ### Resolved Issues * CLI: Resolved an issue where Diffblue Cover could behave unreliably when using `--new-jacoco-coverage` with missing coverage data. Cover now warns users if JaCoCo `.exec` files are empty and provides a reason for keeping newly generated tests. \[Ref: TG-23297] * Resolved an issue where Diffblue Cover would report an `F009` (Internal Error) when encountering a Java `InternalError`. This fix correctly handles `InternalError` ensuring tests are written for previously affected methods. \[Ref: TG-23265] * Resolved an issue that caused Diffblue Cover to report an `F009` (Internal Error) when encountering corrupt files, such as broken `.jar` archives, on the classpath. \[Ref: TG-23263] * Plugin: Resolved an issue causing the IntelliJ UI to become unresponsive when writing tests for large scopes. Test preparation is now an optimized background task, ensuring the UI remains interactive and test generation starts faster. \[Ref: TG-23012] * Resolved an issue where Diffblue Cover would incorrectly report `E054` (No class files found) for modules without source files. It now reports `E129` (No source files found) to reduce confusion and improve diagnostics. \[Ref: TG-21053] ### Known Issues * Plugin: Cover incorrectly provides a menu option to write tests for a test file. \[Ref: TG-17163] * Cover supports Open JDK and Oracle JDK; results with other JDKs may differ due to the variability in their implementations of Java. \[Ref: TG-19345] * Reports: Cover only counts Java code towards the total line count metrics. Kotlin code is not currently 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] * In some circumstances, 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" can be malformed. \[Ref: TG-22805] * Cover does not currently support Java 24. Please switch your JDK version to 21 or lower. \[Ref: TG-22920] --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://cover-docs-preview.diffblue.com/updates-and-upgrades/release-archive/2025-06-02.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.