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pietrobraione / tardis

The TARDIS concolic test case generator
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test test-generation testing-tools

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TARDIS

About

TARDIS (meTAheuRistically-driven DynamIc Symbolic execution) is an automatic test case generator for Java programs, aimed at achieving high branch coverage. It leverages a technique called dynamic symbolic (a.k.a. "concolic") execution, to alternate symbolic execution performed with the symbolic executor JBSE, with test case generation, performed by finding solutions to symbolic execution path constraints with the test case generator EvoSuite.

TARDIS aims at preserving the main advantages of SUSHI and, at the same time, improving performance when information on invariants is missing.

Installing TARDIS

There are two ways to install TARDIS. The easiest is via Docker; The less easy is by building it from source and deploying it on your local machine. In both cases we support only the head revision of the master branch. Formal releases will be available when TARDIS will be more feature-ready and stable.

Installing TARDIS via Docker

A convenient package is available from the TARDIS GitHub page, that allows you to install a Docker image containing a setup of TARDIS and some examples to play with. From the command line run:

$ docker pull ghcr.io/pietrobraione/tardis:master

Alternatively, download the Dockerfile to the current directory and from the command line run:

$ docker build -t tardis .
$ docker run -it tardis

The resulting environment is an Ubuntu container, where at the current (/root) directory you will find a clone of the head revision of the master branch of the TARDIS and of the tardis-experiments repositories.

Building TARDIS

TARDIS is composed by several projects, some of which are imported as git submodules, and is built with Gradle version 8.4, that is included in the repository. First, ensure that all the dependencies are present, including Z3 (see section "Dependencies"). Then, clone the TARDIS git repository and init/update its submodules. If you work from the command line, this means running first git clone, and then git submodule init && git submodule update. Next, follow the instructions described in the section "Patching the tests" of the README.md file of the JBSE subproject. Finally, run the build Gradle task, e.g. by invoking gradlew build from the command line.

Dependencies

TARDIS has many dependencies. It must be built using a JDK version 8 - neither less, nor more. We suggest to use the latest Eclipse Temurin from Adoptium v8 with HotSpot JVM (note that the JDK with the OpenJ9 JVM currently does not work, because there are some slight differences in the standard library classes). If you are on an Apple Silicon Mac we suggest to use the JDK Zulu distribution from Azul. The Gradle wrapper gradlew included in the repository will take care to select the right version of Java. Gradle will automatically resolve and use the following compile-time-only dependencies:

The runtime dependencies that are automatically resolved by Gradle and included in the build path are:

Another runtime dependency that is included in the git project is:

There is one additional runtime dependencies that is not handled by Gradle so you will need to fix it manually.

Finally, two runtime dependencies that are not currently used by TARDIS at runtime, but might be in future, are:

Gradle will download them to compile SUSHI-Lib, but you can avoid to deploy them.

Working under Eclipse

If you want to build (and possibly modify) TARDIS by using (as we do) the latest Eclipse for Java Developers, you are lucky: All the Eclipse plugins that are necessary to import and build TARDIS are already present in the distribution. The only caveat is that, since starting from version 2020-09 Eclipse requires at least Java 11 to run, your development machine will need to have both a Java 11 or greater (to run Eclipse) and a Java 8 setup (to build and run JBSE and TARDIS). Gradle will automatically select the right version of the JDK when building TARDIS. If you use a different flavor, or an earlier version, of Eclipse you might need to install the egit and the Buildship plugins, both available from the Eclipse Marketplace. After that, to import TARDIS under Eclipse follow these steps:

In the end, your Eclipse workspace should contain these projects:

Deploying TARDIS

Deploying TARDIS outside the build environment to a target machine is tricky. The gradlew build command will produce a SUSHI-Lib jar runtime/build/libs/sushi-lib-<VERSION>.jar, the JBSE jars in jbse/build/libs (refer to the JBSE project's README file for more information on them), and a jar for the main TARDIS application master/build/libs/tardis-master-<VERSION>.jar. Moreover, it will copy all the dependencies of the SUSHI-Lib, JBSE and TARDIS projects in runtime/deps, jbse/deps, and master/deps respectively. You need to deploy all of them plus the native files (Z3). The build process will also produce an uber-jar master/build/libs/tardis-master-<VERSION>-shaded.jar containing all the runtime dependencies excluded EvoSuite, tools.jar, and the native files. Deploying based on the uber-jar is easier, but to our experience a setup based on the uber-jar is more crash-prone (on the other hand, using the uber-jar for JBSE is safe).

Here follow detailed instructions for deploying TARDIS based on the plain jars:

You can study the Dockerfile as an example of an automatic deployment workflow on Ubuntu.

If you deploy the tardis-master-<VERSION>-shaded.jar uber-jar you do not need to deploy the JBSE, SUSHI-Lib, args4j, Javaparser, Javassist and Log4J 2 jars.

Usage

Compile the target program with the debug symbols, then launch TARDIS either from the command line or from another program, e.g., from the main of an application. In the first case you need to invoke it as follows:

$ java -Xms16G -Xmx16G -cp <classpath> tardis.Main <options>

where <classpath> must be set according to the indications of the previous section. (Note that TARDIS is resource-consuming, thus we increased to 16 GB the memory allocated to the JVM running it). If you prefer to invoke TARDIS programmatically, this is a possible template of a launcher class:

import tardis.Main;
import tardis.Options;

public final class Launcher {
  public static void main(String[] args) {
    final Options o = new Options();
    o.setZ3Path(...);
    o.setTargetClass(...);
    ...
    final Main m = new Main(o);
    m.start();
  }
}

The launcher must create a tardis.Options object, configure it with the necessary options, then it must create a tardis.Main object and pass to its constructor the previously configured tardis.Options object. Finally, it must invoke the tardis.Main.start() method. Note that the command line TARDIS launcher is not much different from this example, the main difference being that the command line launcher parses the command line arguments to create the tardis.Options object.

Shall you launch TARDIS via the command line or programmatically, you will need to set a number of options for it to work. The indispensable ones, that you must set in order to obtain any result, are:

There are many more options that allow to control several aspects of TARDIS behaviour. You can see a synthetic description of all of them by invoking TARDIS from the command line with the -help option.

A possible example of command line invocation is the following:

$ java -Xms16G -Xmx16G -cp /usr/lib/jvm/java-8-openjdk-amd64/lib/tools.jar:./libs/tardis-master-0.2.0-SNAPSHOT.jar:./libs/sushi-lib-0.2.0-SNAPSHOT.jar:./libs/jbse-0.11.0-SNAPSHOT-shaded.jar:./libs/evosuite-shaded-1.2.1-SNAPSHOT.jar:./libs/args4j-2.32.jar:./libs/log4j-api-2.14.0.jar:./libs/log4j-core-2.14.0.jar:./libs/javaparser-core-3.15.9.jar tardis.Main -jbse_lib ./libs/jbse-0.11.0-SNAPSHOT-shaded.jar -sushi_lib ./libs/sushi-lib-0.2.0-SNAPSHOT.jar -evosuite ./libs/evosuite-shaded-1.2.1-SNAPSHOT.jar -z3 /usr/bin/z3 -classes ./my-application/bin -target_class my/Class -tmp_base ./tmp -out ./tests

where we assume that all the jars except for tools.jar are in ./libs, that the software to be tested is in ./my-application/bin, that the class to generate tests for is my.Class, that a work directory where TARDIS can put intermediate files is ./tmp, and that we want TARDIS to emit the generated tests in ./tests. In the case you prefer (at your own risk) to use the TARDIS uber-jar the command line invocation becomes a bit, but not that much, shorter:

$ java -Xms16G -Xmx16G -cp /usr/lib/jvm/java-8-openjdk-amd64/lib/tools.jar:./libs/tardis-master-0.2.0-SNAPSHOT-shaded.jar:./libs/evosuite-shaded-1.2.1-SNAPSHOT.jar tardis.Main -jbse_lib ./libs/tardis-master-0.2.0-SNAPSHOT-shaded.jar -sushi_lib ./libs/tardis-master-0.2.0-SNAPSHOT-shaded.jar -evosuite ./libs/evosuite-shaded-1.2.1-SNAPSHOT.jar -z3 /usr/bin/z3 -classes ./my-application/bin -target_class my/Class -tmp_base ./tmp -out ./tests

There is a third way of launching TARDIS that mixes the two approaches: You can launch it from the command line, but by configuring the options through an object of class tardis.Options. At the purpose you must define a class implementing the interface tardis.OptionsConfigurator. This interface declares only one method configure, that you must override to configure a tardis.Options object as in the following example:

import tardis.Options;
import tardis.OptionsConfigurator;

public final class MyConfigurator implements OptionsConfigurator {
  @Override
  public void configure(Options o) {
    o.setZ3Path(...);
    o.setTargetClass(...);
    ...
  }
}

As you can see, the resulting code resembles that of a TARDIS launcher, but you do not need to explicitly create the tardis.Options object (it is received as a parameter) nor to create the tardis.Main object and start it. Once created your configurator class, compile it (remember to put the tardis-master jar in the compilation classpath), put the generated classfile where you prefer and invoke TARDIS as follows:

$ java -Xms16G -Xmx16G -cp /usr/lib/jvm/java-8-openjdk-amd64/lib/tools.jar:./libs/tardis-master-0.2.0-SNAPSHOT.jar:./libs/sushi-lib-0.2.0-SNAPSHOT.jar:./libs/jbse-0.11.0-SNAPSHOT-shaded.jar:./libs/evosuite-shaded-1.2.1-SNAPSHOT.jar:./libs/args4j-2.32.jar:./libs/log4j-api-2.14.0.jar:./libs/log4j-core-2.14.0.jar:./libs/javaparser-core-3.15.9.jar tardis.Main -options_config_path ./my-config -options_config_class MyConfigurator

(here we assume that we put the MyConfigurator.class classfile in the ./my-config directory). You will find examples of both launcher and configurator classes in the tardis-experiments project.

Running TARDIS from the Docker environment

Under the Docker environment you can find a more convenient tardis script that is installed on the PATH. When invoked, it runs java, passes to it the classpath and some of the indispensable options, and starts tardis.Main. This allows you to invoke TARDIS as follows:

$ tardis <options>

relieving you from most of the command line boilerplate. More precisely, you do not need to pass the -java8_home, -evosuite, -jbse_lib, -sushi_lib and -z3 options, because the script does it already for you. This way the previous example commands become much shorter:

$ tardis -classes ./my-application/bin -target_class my/Class -tmp_base ./tmp -out ./tests

with the options on the command line, and

$ tardis -options_config_path ./my-config -options_config_class MyConfigurator

with the configurator classes. The tardis script is at /usr/local/bin in the case you want to study it.

If you want to run TARDIS on the pre-built tardis-experiments subjects included in the Docker image you can exploit the configurators and the launchers included in the tardis-experiments project. For instance, if you want to generate tests for the AVL tree example, you can run the following command using the configurator:

$ tardis -options_config_path /root/tardis-experiments/bin -options_config_class avl.AvlConfigurator

or you can invoke the launcher as follows:

$ java -cp ${CLASSPATH}:/root/tardis-experiments/bin avl.RunAvl

See the README.md file of the tardis-experiment project for more information on where the configurators and the launchers are. TARDIS will put the generated tests in /root/tardis-experiments/tardis-test and the intermediate files in a subdirectory of /root/tardis-experiments/tardis-out.

Generated tests

The generated tests are in EvoSuite format, where a test suite is composed by two classes: a scaffolding class, and a class containing the actual test cases (the actual suite). In case the -evosuite_no_dependency option is active, the scaffolding class will not be generated, and the suite will be composed by the actual suite class only: Note, however, that without scaffolding the tests might be flaky. TARDIS will produce many suites each containing exactly one test case: If, e.g., a run of TARDIS generates 10 test cases, then in the directory indicated with the -out command line parameter you will find 10 scaffolding classes, and 10 actual test suite classes each containing exactly 1 test case. Note that all these classes depend on the JUnit and EvoSuite jars, therefore you will need to put these jars on the classpath when compiling and running the test suites. If the -evosuite_no_dependency option is active, the tests will not depend on EvoSuite so you will not need to put the EvoSuite jar on the classpath.

The names of the generated files are structured as follows:

<class name>_<number>_Test_scaffolding.java //the scaffolding class
<class name>_<number>_Test.java             //the actual suite class

where <class name> is the name of the class under test, and <number> is a sequential number that distinguishes the different generated classes, and that roughly reflects in which order the tests were generated.

The generated scaffolding/actual suite classes are declared in the same package as the class under test, so they can access its package-level members. This means, for example, that if you have specified the option -out /your/out/dir, an avl_tree.AvlTree class under test will produce a test /your/out/dir/avl_tree/AvlTree_1_Test.java. If you want to compile and execute the test suites add the output directory to the classpath and qualify the class name of the test suite with the package name, e.g.:

$ javac -cp junit.jar:evosuite-shaded-1.2.1-SNAPSHOT.jar:avltree.jar /your/out/dir/avl_tree/AvlTree_1_Test.java
$ java -cp junit.jar:evosuite-shaded-1.2.1-SNAPSHOT.jar:avltree.jar:/your/out/dir org.junit.runner.JUnitCore avl_tree.AvlTree_1_Test

Disclaimer

TARDIS is a research prototype. As such, it is more focused on functionality than on usability. We are committed to progressively improving the situation.