Cover CLI Usage

Scripts

To execute the Cover CLI, the following scripts are available:

  • dcover.bat (Windows)
  • dcover (Linux/macOS)

These should be run in the root of a single-module project or within a module of a multi-module project.

Windows

Example:

dcover create com.acme.MyClass --test-output-dir=src\test\diffblue

Create tests only for the class com.acme.MyClass and save those tests to src\test\diffblue (default: src\test\java)

Linux/macOS

Example:

dcover create com.acme.MyClass --test-output-dir=src/test/diffblue

Create tests only for the class com.acme.MyClass and save those tests to src/test/diffblue (default: src/test/java)

Commands

All invocations of dcover take one of the following subcommands create, clean or coverage-diff.

create

Example:

dcover create

By default dcover automatically discovers all the packages and writes tests for all of them. You can tell dcover to only write tests for specific packages, classes or methods by specifying one or more prefixes:

dcover create com.a

This will produce tests for all accessible functions within package com.a (but none for any other classes)

Additional optional arguments

--batch

Use this option to run Cover non-interactively, e.g. in CI, in order not to clutter the CI logs with progress bar output.

--class-name-template

Example:

--class-name-template=\${CLASS_NAME}Test, default: --class-name-template=\${CLASS_NAME}DiffblueTest

Specifies how to name the test class files that are generated. The variable ${CLASS_NAME} will be substituted with the name of the class under test. The $ must be escaped.

For example, with the argument given above, and a class name Foo, the name of the class file generated will be FooTest.java. If this argument is specified without the variable ${CLASS_NAME}, all of the tests will be put into one file named by the string in the argument.

--method-name-template, default: ${METHOD_NAME}Test

Example:

Specifies how to name the test methods that are generated. The variable ${METHOD_NAME} will be substituted with the name of the method under test. Similar to --class-name-template.

--classpath or -cp

By default dcover automatically determines the classpath for your project from Maven or Gradle. For projects where that isn't possible, you can set the classpath with this option. For example:

-cp "target/classes:~/.m2/repository/junit/junit/4.12/junit-4.12.jar"

Provide the classpath(s) of the project you want to generate tests for. Multiple paths can be specified using : as separators for Linux/macOS and ; for Windows. jar files can also be added to the classpath as shown above.

Please note that on Windows the classpath argument -cp must be wrapped in double quotes

If this argument is used, you must ensure JUnit (and any other dependencies required to run the project's unit tests) are on the classpath in order for the tests to be verified.

--clear-index

Clear any cached index data and recompute the index from scratch. This may help if the class information used by dcover seems to be outdated or corrupted.

--compliance-level

By default dcover automatically determines the Java compliance level ("Java version") being used. You can set it explicitly with this option.

Example:

--compliance-level=[3-13], default: --compliance-level=8

Specifies the Java Compiler Compliance Level (as an integer). Versions 3 to 13 are supported. The default value is 8.

Class files compiled on a newer version of the Java Compiler may not run on older versions of the JVM. This flag can be set to force the compiler to generate class files corresponding to the specified Java version.

Use this argument if your project is designed to be compiled against a specific Java version other than your default.

--config

Example:

--config path/to/config.json

Provides a path to a file containing json in the configuration format (see --example-config). All of the options listed in this help file can be specified in the configuration json file, plus some others. The additional options that can be specified in the configuration json are:

  • Style

    • output comments, default: enabled

      If enabled, prints comments in the test to designate sections, e.g. // Act, // Arrange, // Assert.

    • inline constants, default: enabled

      If enabled, constants of immediate values (unboxed and boxed primitives, strings, enums, nulls) are inlined into function calls. If disabled, these will be represented with intermediate variables.

    • inline constructors, default: enabled

      If disabled, objects created by calls to constructors will be represented with intermediate variables. If enabled, calls to constructors will be inlined into method calls if possible.

    • arrange into act assert, default: enabled

      If disabled, the test will be separated into an arrange section which sets up all of the variables for the call to the method under test and/or asserts. If enabled, values that can be inlined into the call to the method under test or asserts will be inlined.

    • act into assert, default: enabled

      If disabled, the result of the call to the method under test will be stored in an intermediate variable. If enabled, the call to the method under test will be inlined into an assert statement if possible.

--example-config

If specified, an example configuration file will be output to the command line, then the options can be modified to suit the project and saved in a file. If the command is run from a project's root, dcover will attempt to infer some values for the configuration file, e.g., the packages in the project and --classpath.

--exclude or -E

Example:

--exclude com.x.y. --exclude com.x.y.Foo --exclude com.x.y.Foo.bar:()V

For excluding problematic methods from test generation. Any test method with a fully-qualified name starting with an exclusion pattern will be excluded. The union of methods matched by the arguments is excluded from the set of included methods.

The exclusion argument may be a package name (use trailing .) or a fully-qualified class or method name. You may specify a trailing method signature if differentiating between overloaded methods.

--disable-security-policy

Uses a more permissive security manager policy for the methods under test. Use with caution! This option allows execution of potentially unsafe code during test generation, which may change the file system. Existing files will not be changed or deleted, but new files may be created.

--existing-coverage or -e

Example:

--existing-coverage=target/jacoco.exec

Takes a path to a JaCoCo coverage report ("target/jacoco.exec" here) as an argument, so that dcover will write tests only for those lines of code which are not already covered by existing tests.

Note 1: if using the JaCoCo coverage, --merge must be used (otherwise the tests that produce the coverage, would be replaced!).

Note 2: there are known issues with PowerMock and JaCoCo that can interfere with the usage of this feature:

https://github.com/powermock/powermock/wiki/Code-coverage-with-JaCoCo

--ignore-stylechecks

Example:

--ignore-stylechecks=true, default: --ignore-stylechecks=false

When set, dcover will suppress known style checking plugins (checkstyle, spring-javaformat) during test verification; style checks may prevent compilation or test execution. Currently only supported by Maven projects.

--merge

Example:

--merge=true, default: --merge=false

If enabled and the .java test file already exists, the created tests are inserted into the appropriate file. If the file already contains tests for the same method, then the existing tests will be kept and therefore the file will contain both the existing and newly-generated tests.

If disabled, any existing .java test file will be overwritten and contain only the newly-generated tests.

--mock

Example:

--mock io.diffblue.packagetomock io.diffblue.otherpackage.ClassToMock

dcover will mock non-static classes that match the given prefixes using Mockito. Non-void, non-private instance methods are stubbed with when().thenReturn(). The class containing the method for which the tests are being created will not be mocked. The project configuration must contain a test dependency for Mockito.

--patch-only or -p

Example:

--patch-only=path/to/patch-file

By specifying a patch-file, it is possible to create tests only for the code changes covered by the patch.

Use diff or a similar tool to create a patch-file for your changes.

--report

Example:

--report=path/to/report.json

Write JSON-formatted test-writing summary report to the file specified.

--target-directory, default: .diffblue

Example:

--target-directory=target/directory

Set the directory for storing dcover's working files and logs.

--skip-test-verification

By default, generated tests are compiled and executed to make sure they are correct, and only those which succeed will be kept. Sometimes this results in all the tests being deleted due to style checks failing (see --ignore-stylechecks above), and it increases test creation time, so it may be desirable to skip verification via this option. For test verification to work, JUnit must be on the classpath. Normally dcover automatically takes care of this, but if you are using a manual classpath don't forget to add it.

--test-output-dir or -d

Example:

--test-output-dir=src/test/diffblue, default: src/test/java

Location for the generated tests relative to the working directory. Provide the relative path for the directory where generated tests should be placed.

See --working-directory.

--testing-framework

By default dcover automatically determines the version of JUnit in use by your project. You can override it with this option.

Example:

--testing-framework=junit-5.6

Supported values:

The supported values for this option are the versions of JUnit from junit-4.7 to junit-5.6. If you choose to supply this option the classpath will be checked to see if that framework is available. If there is a mismatch between versions dcover will produce an error.

--verbose

If enabled, prints more detailed log messages about the test generation process.

--verification-command or -x

By default dcover uses the standard Maven or Gradle test command to verify tests. You can override that with this option.

  • Maven:

    • If no command is provided, "mvn test" is run if dcover detects a pom file in the working directory. When the command fails for a certain test method, dcover will revert the entire test class containing that method.
  • Gradle:

    • If no command is provided, "gradle test" is run if dcover detects a Gradle project in the working directory. When the command fails for a certain test method, dcover will revert the entire test class containing that method.

Example:

--verification-command "mvn test"

The given command is executed after tests have been generated to make sure they do not break the build. Tests are removed if it returns a non-zero exit value.

All existing tests should pass the verification command before dcover is invoked; there should be no pre-existing compilation or test failures.

--verification-timeout

Example:

--verification-timeout=duration, default: --verification-timeout=30m

Specifies how long test verification may take before being cancelled.

Supported values:

A positive integer value with one of the following suffixes: h for hours, m for minutes, or s for seconds.

If 0 (zero) is specified, the test verification will not timeout.

--working-directory

Example:

--working-directory=path/to/module

Sets the working directory for running dcover, enabling the user to run dcover for a particular module, for example, from the root of a project.

clean

Example:

dcover clean

The clean command removes test methods written by dcover that no longer compile due changes in the project.

As with create, if the package prefixes following clean are omitted, dcover will infer the packages from the directory structure.

These additional optional arguments can also be provided:

--batch

As with create above, use this option to run dcover non-interactively.

--class-name-template, default: --class-name-template=\${CLASS_NAME}DiffblueTest

Example:

--class-name-template=\${CLASS_NAME}Test

The template for locating generated test classes. As with create --class-name-template above, the variable ${CLASS_NAME} will be substituted with the name of the class under test. The $ must be escaped. This should match the --class-name-template used to with dcover create to generate the tests.

--method-name-template, default: ${METHOD_NAME}Test

Specifies how to name the test methods that are generated. The variable ${METHOD_NAME} will be substituted with the name of the method under test. Similar to --class-name-template. This should match the --method-name-template used to with dcover create to generate the tests.

--compliance-level

Example:

--compliance-level=[3-13], default: --compliance-level=8

Specifies the Java Compiler Compliance Level (as an integer) that the generated tests were written with. See create --compliance-level above for further details.

--classpath or -cp

As for dcover create, allows manual setting of the classpath. See create -cp above for further details.

--test-output-dir or -d

Example:

--test-output-dir=src/test/java

The output directory for generated tests from which methods and classes will be cleaned. See create --test-output-dir above for further information.

--target-directory, default: .diffblue

Example:

--target-directory=target/directory

Set the directory for storing dcover's working files and logs.

--testing-framework

See create --testing-framework above for further information.

--verbose

If enabled, prints more detailed log messages about the test clean process.

--working-directory, default: .

Example:

--working-directory=path/to/module

Sets the working directory for running dcover, enabling the user to run dcover for a particular module, for example, from the root of a project.

--failing

When enabled, instead of deleting non-compiling tests, dcover clean deletes any failing test classes.

coverage-diff

Example:

dcover coverage-diff target/jacocoOld.exec target/jacocoNew.exec

For visualizing the new coverage gained by writing tests with Diffblue Cover CLI.

Generates an HTML report highlighting the difference between two supplied JaCoCo coverage reports.

Please see "Generating an HTML report highlighting new coverage" in the User guide for more information.

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