Getting Started


Using the Verifier consists out of three different phases

  1. Configure
  2. Run
  3. Verify


The Verifier instance is constructed in the simplest case with just one argument taking the path name of the base directory containing the pom.xml of the project you want to build.

String baseDir = ...
Verifier verifier = new Verifier( baseDir );

The configuration can be further tweaked with additional setter methods and/or constructors taking more parameters.

System Properties

The following system properties are evaluated. None of them are required and in most cases the same behavior can also be achieved through constructor or setter method programmatically.

System Property Description Default Value
verifier.forkMode The following values are supported:
auto uses the forked launcher when environment variables are set
embedder always uses the embedded launcher
any other value leads to always using the forked launcher
maven.home The directory containing the Maven executable in bin/mvn not set
user.home Set by JRE, used for determining Maven default local repository path or the fallback Maven executable always set by JRE
maven.bootclasspath Only relevant if Maven home could be determined and the embedded launcher is being used. Determines the classpath of the launcher. May contain multiple paths separated by the system specific path separator. not set (using all JARs below <Maven Home>/boot as class path)
classworlds.conf Only relevant if Maven home could be determined and the embedded launcher is being used. The configuration file used by Plexus Classworlds Loader. <Maven Home>/bin/m2.conf
maven.repo.local Contains the path of the local Maven repository Either repository path set in settings.xml or <User Home>/.m2/repository
maven.repo.local.layout Layout of the local Maven repository. Either legacy or default default

Finding Maven Executable

The following mechanism determines the binary which is used for executing Maven. This is

  • either the embedded launcher which uses
    • the org.apache.maven.cli.MavenCli class loaded from the context class loader (in case Maven Home could not be determined) or
    • the Plexus Classworlds Loader (in case Maven Home could be determined)
  • or the forked launcher

Whether the embedded or the forked launcher are used depends on the field forkJvm set through the constructor or setForkJvm or as fallback on the value of system property verifier.forkMode.

Determining Maven Home Directory

The following directories are considered as potential Maven home directory (relevant for both forked launcher and embedded launcher with Plexus Classworlds Loader). The first existing directory from the list is used.

  1. Maven Home path given in the constructor
  2. System property maven.home

Setting Maven Home for Embedded Launcher

In order to pass Maven Home used for executing project itself to tests execution, maven-surefire can be configured like:


Class Path For Embedded Launcher

In case when Maven Home Directory can not be determined, to use the embedded launcher it is important that some artifacts are in the class path. For the Context Class Loader case this would mean the following dependencies are needed at least (for Maven 3.8.4):

<!-- embedder for testing Embedded3xLauncher with classpath -->
<!-- START transitive dependencies of embedder -->
<!-- required due to -->


Calling execute() runs Maven with the given Verifier configuration, like CLI arguments and environment variables. At least one CLI argument should be provided which specifies either the Maven phase(s) and/or the goal(s) to execute unless project has a default goal.

It throws a VerificationException in case the execution is not successful (e.g. binary not found or exit code > 0). The method is using either a forked JVM or the same JVM for executing Maven depending on the configuration.

verifier.addCliArgument( "package" )


After calling execute one should call one or multiple of the methods starting with prefix verify to

  • check for the build result
  • check the log for certain contents or
  • check for the existence of generated artifacts.

The main method verify(boolean) takes into consideration a file named expected-results.txt being located in the tested project's base directory. Each line consists of a file path (optionally prefixed by !) and it is automatically verified that the file exists or is missing (in case the path starts with !).

verifier.verify( true ); // if true, throws an exception in case of errors in the build log