What's New > Version 2020.12.01

Enhancements to mocking void methods and improvements to generated assertions

Release date: Dec 08, 2020

Mocking void methods

When mocking void methods, we now add a Mockito.verify() statement which asserts on the number of invocations, this allows you to get a test even if there isn’t anything else to assert on.

verify(this.simpleService_AdditionService, times(2)).makeAGoodGuess(anyInt(), anyInt());

Asserting on methods that return a boolean

Assertions are now generated for both true and false values of methods that return a bool value from straight-line code.

public void testIsAssignableFrom() {
  // Arrange, Act and Assert

Cover gives you tests when we can’t find assertions

@Test public void testSetVisitsInternal() {
    // TODO: This test is incomplete - see https://diff.blue/R004
    //  Reason: No meaningful assertions found.
    //  To help Diffblue Cover to find assertions, please add getters to the
    //  class under test that return fields written by the method under test.
    Pet pet = new Pet();

Sometimes Diffblue Cover can arrange a test and create the objects but can’t find any valid assertions. We will give you these tests and a nice reminder to complete the tests by adding assertions.

Full Release Notes


  • CLI: Cover’s logging, to the console when using --verbose, or to the log file, has been improved so that it is easier to read per-class and per-method messages. [Ref: TG-13323]

  • IntelliJ Plugin: Cover now supports IntelliJ IDEA Community Edition 2020.3 and IntelliJ IDEA Ultimate 2020.3. [Ref: TG-13292]

  • Cover is now able to verify if a mocked method, which returns void, has been called. [Ref: TG-13199]

  • Cover is now able to verify if a mocked method has been called more than once. [Ref: TG-13198]

  • Cover now uses isEmpty(), rather than comparing 0 with list.size(), when writing assertions for empty collections such as a set, list or map. [Ref: TG-13169]

  • Cover is now able to assert on the content of a repository when testing void Repository methods. [Ref: TG-12970]

Resolved Issues

  • IntelliJ Plugin: Resolved an issue where the test classpath wasn’t consulted when writing tests on Gradle projects. [Ref: TG-13301]

  • CLI: Resolved an issue where Cover may fail to download the project’s dependencies on Maven Central. [Ref: TG-13278]

  • CLI: Resolved an issue where tests were discarded with V002 error code for Spring Repositories. [Ref: TG-13274]

  • IntelliJ Plugin: Resolved a cosmetic issue, within Cover’s ‘Spring’ settings, so that it is clearer when mocking will be used. [Ref: TG-13271]

  • IntelliJ Plugin: Resolved an issue where selecting ‘Write tests’ may fail with Could not initialize class oshi.software.os.windows.WindowsOperatingSystem or Failed to create temporary file for /com/sun/jna/win32-x86-64/jnidispatch.dll library. [Ref: TG-13235]

  • IntelliJ Plugin: Resolved an issue where, the JDK path provided to IntelliJ is inaccessible, Failed to start remote test generation service may be logged. Cover now provides improved guidance. [Ref: TG-13200]

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 fails to generate tests, reporting java.lang.OutOfMemoryError, when analysing projects which spawn a quantity of threads in excess of the operating system’s process thread limit. [Ref: TG-11680]

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

  • CLI: Test validation may fail on a Gradle project due to an incompatibility between Gradle and Cover. If you encounter this issue, run with --skip-test-validation. [Ref: TG-12045]

  • IntelliJ Plugin: Large multi-module Gradle projects may take a long time to index. [Ref: TG-12923]