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EvoMaster Driver

To generate tests for white-box testing, you need an EvoMaster Driver up and running before executing evomaster.jar. These drivers have to be built manually for each system under test (SUT). See the EMB repository for a set of existing SUTs with drivers.

To build a client driver in Java (or any JVM language), you need to import the EvoMaster Java client library. For example, in Maven:


In Gradle, it would be:


The placeholder LATEST needs to be replaced with an actual version number (e.g., 1.0.0 or 1.0.0-SNAPSHOT). For the latest version, check Maven Central Repository. The latest version number should also appear at the top of the main readme page. If you are compiling directly from the EvoMaster source code, make sure to use mvn install to install the snapshot version x.y.z-SNAPSHOT of the Java client into your local Maven repository (e.g., under ~/.m2). For the actual x.y.z-SNAPSHOT version number, you need to look at the root pom.xml file in the project. If you are using Gradle, you can for example check on this SO question to see how to do something equivalent to mvn install.

Note: the core application evomaster.jar is independent of the driver library, and it contains none of the driver's classes.

Note: you might also need to import some other libraries (e.g., RestAssured when generating tests for REST APIs runninng on the JVM).

Once the client library is imported, you need to create a class that extends either or Both these classes extend SutController. The difference is on whether the SUT is started in the same JVM of the EvoMaster driver (embedded), or in a separated JVM (external).

The easiest approach (which we recommend) is to use the embedded version, especially when dealing with frameworks like Spring and DropWizard. However, when the presence of the EvoMaster client library gives side-effects (although its third-party libraries are shaded, side-effects might still happen), or when it is not possible (or too complicated) to start the SUT directly (e.g., JEE), it is better to use the external version. The requirement is that there should be a single, self-executable uber/fat jar for the SUT (e.g., Wildfly Swarm). It can be possible to handle WAR files (e.g., by using Payara), but currently we have not tried it out yet.

Once a class is written that extends either EmbeddedSutController or ExternalSutController, there are a few abstract methods that need to be implemented. For example, those methods specify how to start the SUT, how it should be stopped, and how to reset its state. The EvoMaster Java client library also provides further utility classes to help writing those controllers/drivers. For example, helps in resetting the state of a database (if any is used by the SUT).

Note: when implementing a new class, most IDEs (e.g., IntelliJ) have the function to automatically generate empty stubs for all the abstract methods in its super-classes. Also, all the concrete (i.e., non-abstract) methods in EmbeddedSutController and ExternalSutController are marked as final, to prevent overriding them by mistake and so breaking the driver's internal functionalities.

Each of the abstract methods you need to implement does provide Javadocs. How to read those Javadocs depend on your IDE settings (e.g., hovering the mouse over a method declaration). You can also browse them online here.

Once a class X that is a descendant of SutController is written, you need to be able to start the EvoMaster driver, by using the class. For example, in the source code of the class X, you could add:

public static void main(String[] args){

   SutController controller = new X();
   InstrumentedSutStarter starter = new InstrumentedSutStarter(controller);


At this point, once this driver is started (e.g., by right-clicking on it in an IDE to run it as a Java process), then you can use evomaster.jar to finally generate test cases. Note that it is also possible to run the driver from command-line, like any other Java program with a main function. However, in such case, you will need to package an uber jar file (e.g., using plugins like maven-shade-plugin and maven-assembly-plugin).

WARNING: Java 9 broke backward compatibility. And each new JDK version seems breaking more stuff :-(. To deal with recent versions of the JDK, see here for details.

TCP Ports

When writing an EvoMaster driver, there are 2 TCP ports that you need to consider:

  • the port of the driver itself, whose default value is 40100. This can be changed when instantiating a SutController. However, the EvoMaster core process would need to be informed of this different port value (e.g., by using the --sutControllerPort option).

  • the port of the SUT. In general, you will want to set up an ephemeral port (i.e., a free, un-used one) for this (e.g., by using the value 0, and then read back in the driver which port was actually assigned to the server).

Starting The Application

How to start/reset/stop the SUT depends on the chosen framework used to implement the SUT. To implement an EvoMaster Driver class, you need check the JavaDocs of the extended super class, e.g., EmbeddedSutController, and the existing examples in EMB.

As SpringBoot is nowadays the most common way to implement enterprise systems on the JVM, here we provide some discussions / walk-through on how to write a driver for it that extends EmbeddedSutController, using as reference the driver for the features-service SUT in EMB.

To programmatically start a SpringBoot application (needed to implement startSut()), you can use, and save the resulting ConfigurableApplicationContext in variable (e.g., ctx). This will be useful when needing to override the methods isSutRunning() and stopSut(), as you can just implement them with ctx.isRunning() and ctx.stop().

When starting the SUT, there is one important configuration that you want to change: the binding port, as you want to use 0 for ephemeral ports (to avoid port conflicts).

Note: since version 1.3.0, there is no longer the need to configure P6Spy.

For a SUT like features-service, this can be done with:

ctx =, new String[]{

The actual chosen port can then be extracted with:

protected int getSutPort() {
        return (Integer) ((Map) ctx.getEnvironment()

Finally, the startSut() method must return the URL of where the SUT is listening on. When running tests locally, this is as simple as returning "http://localhost:" + getSutPort().

Note that you need to make sure you can run your application programmatically, regardless of EvoMaster. A simple way is to check if the following works:

public static void main(String[] args) {, args);

The issue could arise when using spring-boot-maven-plugin to start the application, and there are some classpath problems in your application.

SQL Databases

If the application is using a SQL database, you must configure getConnection() and getDatabaseDriverName(), instead of leaving their returned values as null. For example, if you are using H2, then the driver name would be org.h2.Driver. In SpringBoot, you can extract a connection object in the startSut() method (and save it in a variable), by simply using:

JdbcTemplate jdbc = ctx.getBean(JdbcTemplate.class);
connection = jdbc.getDataSource().getConnection();

Test cases must be independent from each other. Otherwise, you could get different results based on their execution order. To enforce such independence, you must clean the state of the SUT in the resetStateOfSUT() method. In theory, RESTful APIs should be stateless. If indeed stateless, resetting the state would be just a matter of cleaning the database. For this purpose, we provide the DbCleaner utility class (used to delete data without recreating the database schema). There might be some tables that you might not want to clean, like for example if you are using FlyWay to handle schema migrations. These tables can be skipped, for example:

public void resetStateOfSUT() {
   DbCleaner.clearDatabase_H2(connection, Arrays.asList("schema_version"));

where the content of the table schema_version is left untouched.

If your application uses some caches, those might be reset at each test execution. However, an easier approach could be to just start the SUT without the caches, for example using the option --spring.cache.type=NONE.

Whenever possible, it would be best to use an embedded database such as H2. However, if you need to rely on a specific database such as Postgres, we recommend starting it with Docker.
In Java, this can be done with libraries such as TestContainers (which you will need to import in Maven/Gradle). In your driver, you can then have code like:

private static final GenericContainer postgres = new GenericContainer("postgres:9")
            .withTmpFs(Collections.singletonMap("/var/lib/postgresql/data", "rw"));

Then, the database can be started in startSut() with postgres.start(), and stopped in stopSut() with postgres.stop(). Then, the URL to connect to the database can be something like:

String host = postgres.getContainerIpAddress();
int port = postgres.getMappedPort(5432);
String url = "jdbc:postgresql://"+host+":"+port+"/postgres"

You can then tell Spring to use such URL with the parameter --spring.datasource.url.

Note: the withTmpFs configuration is very important, and it is database dependent. A database running in Docker will still write on your hard-drive, which is an unnecessary, time-consuming overhead. The idea then is to mount the folder, in which the database writes, directly in RAM.

For an example, you can look at the E2E tests in EvoMaster, like the class

MongoDB Database

Although at the current moment EvoMaster does not analyze how MongoDB databases are accessed at runtime, it is important still to reset their state (to avoid dependencies among generated tests). Compared to SQL databases, MongoDB is easier to reset. Can use directly the APIs of MongoDB. For example, given a reference to com.mongodb.MongoClient, you can have:

public void resetStateOfSUT() {

As for any external service, we reccomend to start them with Docker. For example:

private static final GenericContainer mongodb =  
         new GenericContainer("mongo:3.2")

In Spring, the connection URL can then be set with:"+mongodb.getContainerIpAddress()+":"+mongodb.getMappedPort(27017)+"/foo"

Code Coverage

When EvoMaster evolves test cases, it tries to maximize code coverage in the SUT. But there is no much point in trying to maximize code coverage of the third-party libraries, like Spring, Hibernate, Tomcat, etc. Therefore, in the getPackagePrefixesToCover() you need to specify the common package prefix for your business logic. In the case of the features-service SUT, this was org.javiermf.features.

REST OpenApi/Swagger Schema

To test a RESTful API, in the the getProblemInfo(), you need to return an instance of the RestProblem class. Here, you need to specify where the OpenApi schema is found, and whether any endpoint should be skipped, i.e., not generating test cases for. This latter option is useful for example to skip the SpringBoot Actuator endpoints (if any is present).
If your RESTful API does not have an OpenApi/Swagger schema, this can be automatically added by using libraries such as SpringDoc.


The SUT might require authenticated requests (e.g., when Spring Security is used). How to do it must be specified in the getInfoForAuthentication(). We support auth based on authentication headers and cookies. Unfortunately, at the moment we do not support OAuth (we will in the future).

The can be used to simplify the creation of such configuration objects, e.g., by using methods like getForDefaultSpringFormLogin(). Consider the following example from the proxyprint case study in the EMB repository.

public List<AuthenticationDto> getInfoForAuthentication() {
        return Arrays.asList(

Here, auth is done with RFC-7617 Basic. Four different users are defined. When EvoMaster generates test cases, it can decide to use some of those auth credentials, and generate the valid HTTP headers for them. In case of cookies, EvoMaster is able to first make a login request, store the cookie, and then use such cookie in the following HTTP calls in its generated tests.

Although EvoMaster can read and analyze the content of a SQL database, it cannot reverse-engineer the hashed passwords. These must be provided with getInfoForAuthentication(). If such auth info is stored in a SQL database, and you are resetting the state of such database in the resetStateOfSUT() method, you will need there to recreate the login/password credentials as well. You could write such auth setup in a init_db.sql SQL script file, and then in resetStateOfSUT() execute:


Note: at the moment EvoMaster is not able to register new users on the fly with HTTP requests, and use such info to authenticate its following requests.