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Java Concolic Unit Testing Engine
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The Java Concolic Unit Testing Engine (jCUTE) automatically generates unit tests for Java programs. Concolic execution combines randomized concrete execution with symbolic execution and automatic constraint solving. Symbolic execution allows jCUTE to discern inputs that lead down different execution paths; randomized concrete execution helps it overcome limitations of the constraint solver, like the inability to analyze system calls or solve general systems of non-linear integer equations. Through this combination, jCUTE is able to generate test cases that execute many different execution paths in real Java programs.

jCUTE supports multi-threaded programs. It can discover race conditions and deadlocks through systematic schedule exploration.


jCUTE requires an installed and working Java Development Kit (JDK) version 1.4 or later. It expects both java and javac to be in the PATH. To run jCUTE on a 32-bit system, simply download and unzip the binary distribution from the jCUTE homepage. To run jCUTE on a 64-bit system, you will have to build the distribution archive from the sources in this repository; see the instructions below.

  • On Linux, run the setup script. Then execute the jcutegui script.
  • On Windows, run the jcutegui.bat batch file.

The src/ directory contains a number of examples. See the script runtests to know how to run these examples.


  • jcutec is the instrumentor plus compiler script for distributed Java programs under test.
  • jcute is the script to concolically test the executable of the instrumented program under test.


Command line: ./jcutec SOURCE_DIRECTORY MAIN_JAVA_FILE MAIN_JAVA_CLASS -sequential

  • SOURCE_DIRECTORY is the directory containing the sources of the Java program to be tested
  • MAIN_JAVA_FILE is the name of the Java source file containing the main function
  • MAIN_JAVA_CLASS is the name of the class of the Java source file containing the main function

For example, to compile and instrument the Demo example in the directory src/tests in the package tests, execute

./jcutec src/ src/dtests/ dtests.DExample1 -sequential

Concolic Execution

Command line: ./jcute class -i iterations [-?] [-help] [-d DEPTH=0] [-s SEED] [-t DEBUG_LEVEL=0] [-m PATH_MODE=0] [-r] [-q] [-p] [-v] [-a] [-n ARGUMENT=0]

Options include:

  • -help, -?: Displays help information
  • -d <decimal integer>: Depth of search. Default is 0, which implies infinite depth
  • -s <decimal integer>: Seed for random number generator in case -r option is given. Default is current system time.
  • -t <decimal integer>: Various debug information and statistics. Default is 0 (no debug information printed).
    • 1: Print trace of instrumentation function call's entry and exit.
    • 2: Print info about instrumented function call inserted for concurrency.
    • 4: Print input map after reading from disk.
    • 8: Print history at every history change.
    • 16: Print symbolic state at every state change.
    • 32: Print path constraint whenever path constraint is updated.
    • 64: Print old and new history at the end of execution.
    • 128: Print old and new input map at the end of the execution.
    • 256: Print path constraint at the end of the execution.
    • 512: Print line number executed.
  • -m <decimal integer {0,1,2}>: Path selection. Default is 0.
    • 0: Next path (depends on history),
    • 1: Replay last execution,
    • 2: Start fresh execution without looking at any history.
  • -r: If specified, inputs are randomly initialized; else, inputs are set to 0. Objects are initialized to null in either cases.
  • -p: Random search strategy is invoked
  • -q: Record branch coverage information
  • -a: Turn off Optimal Distributed Search
  • -v: Verbose: logs inputs and trace of execution
  • -n <decimal integer>: Pass a single integer argument

For example, to test the Demo example run

./jcute dtests.DExample1 -i 100 -q

To see the statistics about branch coverage and runtime execute

java -classpath jcute.jar cute.concolic.BranchCoverage

Graphical User Interface

In the Graphical user Interface, try selecting the directory src/ and the Java program dtests/ Then "Compile" and "(Re)start" for testing. Click on a Run # to get the Input and Trace log.


Instead of downloading the binary distribution archive, the archive can also be built from the sources in this repository.

Compiling the Constraint Solving Library on Linux

jCUTE uses the lp_solve linear programming library for constraint solving. It comes with pre-compiled 32-bit versions of this C library, which it accesses via the Java Native Interface (JNI). However, the library and the wrapper were compiled against old standard libraries ( that are no longer available on modern Linux systems. A potential solution for this is to install an old 32-bit Linux image into a virtual machine for running jCUTE in it. Another solution is to compile the libraries on one's system.

64-bit Systems

The lp_solve library compiles and appears to work fine on 64-bit systems.

Compiling lp_solve

Compiling the lp_solve Java Wrapper

  • Download the Java wrapper source code archive from
  • Unzip the archive into a temporary directory.
  • Change to the lib/linux/ directory and edit the file build:
    • Set the LPSOLVE_DIR variable to the path that contains lp_lib.h; this should be the lp_solve_5.1/ directory from above.
    • Tell the linker where to find by adding the command line option -L/path/to/containing/dir/ to the second g++ invocation in the build file. Replace /path/to/containing/dir with the path containing
    • Set the JDK_DIR variable to your JDK root directory, for example /opt/java6/ on Arch Linux.
  • Run sh build to build
  • Copy into the jCUTE root directory.

Compiling and Packaging jCUTE

Execute the package shell script in the project's root directory to build the jCUTE JAR file and the distribution archive: sh package.


The jCUTE software is NOT in the public domain. However, it is freely available without fee for education, research, and non-profit purposes as described in the complete jCUTE license. The third-party libraries used by jCUTE are licensed as described in their license files.


jCUTE was designed and implemented by Koushik Sen around 2006.

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