DSpot

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DSpot is a tool that generates missing assertions in JUnit tests. DSpot takes as input a Java project with an existing test suite. As output, DSpot outputs new test cases on console. DSpot supports Java projects built with Maven and Gradle (see the --automatic-builder option)

Getting started

Prerequisites

You need Java and Maven.

Compilation

Clone the project:

git clone https://github.com/STAMP-project/dspot.git
cd dspot/dspot

Compile DSpot

mvn compile

DSpot uses the environment variable MAVEN_HOME, ensure that this variable points to your maven installation. Example:

export MAVEN_HOME=path/to/maven/

Run the tests

mvn test

Create the jar (eg target/dspot-1.0.0-jar-with-dependencies.jar)

mvn package
# check that this is successful
ls target/dspot-*-jar-with-dependencies.jar

Run the jar

java -cp target/dspot-*-jar-with-dependencies.jar fr.inria.stamp.Main -p path/To/my.properties

For more info, see section Usage below.

Releases

See https://github.com/STAMP-project/dspot/releases

Contributing

DSpot is licensed un LGPLv3. Pull request as are welcome.

Usage

First Tutorial

After having cloned DSpot (see the previous section), you can run the provided example by running fr.inria.stamp.Main from your IDE, or with

java -jar target/dspot-LATEST-jar-with-dependencies.jar --example

replacing LATEST by the latest version of DSpot, e.g. 1.1.0 would give : dspot-1.1.0-jar-with-dependencies.jar

This example is an implementation of the function chartAt(s, i) (in src/test/resources/test-projects/), which returns the char at the index i in the String s.

In this example, DSpot amplifies the tests of chartAt(s, i) with the TestDataMutator, which modifies literals inside the test and the generation of assertions.

DSpot first reads information about the project from the properties file src/test/resources/test-projects/test-projects.properties.

#relative path to the project root from dspot project
project=src/test/resources/test-projects/
#relative path to the source project from the project properties
src=src/main/java/
#relative path to the test source project from the project properties
testSrc=src/test/java
#java version used
javaVersion=8
#path to the output folder
outputDirectory=target/trash/
# Constant amount of additional time to allow a test to run for
# before considering it to be stuck in an infinite loop
timeoutConstInMillis=10000
#Argument string to use when PIT launches child processes. This is most commonly used
# to increase the amount of memory available to the process,
# but may be used to pass any valid JVM argument.
# Use commas to separate multiple arguments, and put them within brackets
jvmArgs=['-Xmx2048m','-Xms1024m']

The result of the amplification of charAt consists of 6 new tests, as shown in the output below. These new tests are written to the output folder specified by configuration property outputDirectory (./target/trash/).

======= REPORT =======
Initial instruction coverage: 33 / 37
89.19%
Amplification results with 22 amplified tests.
Amplified instruction coverage: 37 / 37
100.00%

[8411] INFO DSpot - Print TestSuiteExampleAmpl with 22 amplified test cases in target/trash/

Wiki documentation

For a more step by step documentation, see the wiki.

Command Line Usage

Let's imagine you wish to run DSpot on module1. You need to create a properties file (e.g. dspot.properties), that you can locate under module1 and containing (for example):

# Relative path to the project root.
project=..
# Path to the current module where we want to execute DSpot, relative to the project root
targetModule=module1/
# Relative path to the source project from this properties file
src=src/main/java/
# Relative path to the test source project from this properties file
testSrc=src/test/java
# Java version used
javaVersion=8
# (Optional) Path to the output folder, default to "output_diversify"
outputDirectory=dspot-out/

You can then execute DSpot by using:

java -jar /path/to/dspot-LATEST-jar-with-dependencies.jar --path-to-properties dspot.properties
# or in maven
mvn exec:java -Dexec.mainClass="fr.inria.stamp.Main" -Dexec.args="--path-to-properties dspot.properties"

Amplify a specific test class

java -jar /path/to/dspot-*-jar-with-dependencies.jar fr.inria.stamp.Main --path-to-properties dspot.properties --test my.package.TestClass

Amplify specific test classes according to a regex

java -jar /path/to/dspot-LATEST-jar-with-dependencies.jar --path-to-properties dspot.properties --test my.package.*
java -jar /path/to/dspot-LATEST-jar-with-dependencies.jar --path-to-properties dspot.properties --test my.package.Example*

Amplify a specific test method from a specific test class

java -jar /path/to/dspot-LATEST-jar-with-dependencies.jar --path-to-properties dspot.properties --test my.package.TestClass --cases testMethod

Usage: java -jar target/dspot-<version>-jar-with-dependencies.jar
                          [(-p|--path-to-properties) <./path/to/myproject.properties>] [(-a|--amplifiers) Amplifier1:Amplifier2:...:AmplifierN ] [(-i|--iteration) <iteration>] [(-s|--test-criterion) <PitMutantScoreSelector | ExecutedMutantSelector | CloverCoverageSelector | JacocoCoverageSelector | TakeAllSelector | ChangeDetectorSelector>] [--max-test-amplified <integer>] [(-t|--test) my.package.MyClassTest1:my.package.MyClassTest2:...:my.package.MyClassTestN ] [(-c|--cases) testCases1:testCases2:...:testCasesN ] [(-o|--output-path) <output>] [--clean] [(-m|--path-pit-result) <./path/to/mutations.csv>] [--descartes] [--automatic-builder <MavenBuilder | GradleBuilder>] [--maven-home <path to maven home>] [--randomSeed <long integer>] [--timeOut <long integer>] [--verbose] [--with-comment] [--no-minimize] [-e|--example] [-h|--help]

  [(-p|--path-to-properties) <./path/to/myproject.properties>]
        [mandatory] specify the path to the configuration file (format Java
        properties) of the target project (e.g. ./foo.properties).

  [(-a|--amplifiers) Amplifier1:Amplifier2:...:AmplifierN ]
        [optional] specify the list of amplifiers to use. Default with all
        available amplifiers.
        		 - StringLiteralAmplifier
        		 - NumberLiteralAmplifier
        		 - CharLiteralAmplifier
        		 - BooleanLiteralAmplifier
        		 - AllLiteralAmplifiers
        		 - MethodAdd
        		 - MethodRemove
        		 - TestDataMutator (deprecated)
        		 - StatementAdd
        		 - ReplacementAmplifier
        		 - None (default: None)

  [(-i|--iteration) <iteration>]
        [optional] specify the number of amplification iterations. A larger
        number may help to improve the test criterion (eg a larger number of
        iterations may help to kill more mutants). This has an impact on the
        execution time: the more iterations, the longer DSpot runs. (default: 3)

  [(-s|--test-criterion) <PitMutantScoreSelector | ExecutedMutantSelector | CloverCoverageSelector | JacocoCoverageSelector | TakeAllSelector | ChangeDetectorSelector>]
        [optional] specify the test adequacy criterion to be maximized with
        amplification (default: PitMutantScoreSelector)

  [--max-test-amplified <integer>]
        [optional] specify the maximum number of amplified tests that dspot
        keeps (before generating assertion) (default: 200)

  [(-t|--test) my.package.MyClassTest1:my.package.MyClassTest2:...:my.package.MyClassTestN ]
        [optional] fully qualified names of test classes to be amplified. If the
        value is all, DSpot will amplify the whole test suite. You can also use
        regex to describe a set of test classes. (default: all)

  [(-c|--cases) testCases1:testCases2:...:testCasesN ]
        specify the test cases to amplify

  [(-o|--output-path) <output>]
        [optional] specify the output folder (default: dspot-report)

  [--clean]
        [optional] if enabled, DSpot will remove the out directory if exists,
        else it will append the results to the exist files. (default: off)

  [(-m|--path-pit-result) <./path/to/mutations.csv>]
        [optional, expert mode] specify the path to the .csv of the original
        result of Pit Test. If you use this option the selector will be forced
        to PitMutantScoreSelector

  [--descartes]
        Enable the descartes engine for Pit Mutant Score Selector.

  [--automatic-builder <MavenBuilder | GradleBuilder>]
        [optional] specify the automatic builder to build the project (default:
        MavenBuilder)

  [--maven-home <path to maven home>]
        specify the path to the maven home

  [--randomSeed <long integer>]
        specify a seed for the random object (used for all randomized operation)
        (default: 23)

  [--timeOut <long integer>]
        specify the timeout value of the degenerated tests in millisecond
        (default: 10000)

  [--verbose]
        Enable verbose mode of DSpot.

  [--with-comment]
        Enable comment on amplified test: details steps of the Amplification.

  [--no-minimize]
        Disable the minimization of amplified tests.

  [-e|--example]
        run the example of DSpot and leave

  [-h|--help]
        show this help

Configuration

Here is the list of configuration properties of DSpot:

required properties:
- project: path to the project root directory.
- src: relative path (from project properties) to the source root directory.
- testSrc: relative path (from project properties) to the test source root directory.
recommended properties:
- outputDirectory: path to the out of dspot. (default: output)
- javaVersion: version used of Java (default: 5)
- maven.home: path to the executable maven. If no value is specified, it will try some defaults values (for instance: /usr/share/maven/, usr/local/Cellar/maven/3.3.9/libexec/ ...).
optional properties:
- filter: filter on the package name containing tests to be executed (e.g. example.*) passed to Pitest. If not set, the default value is set automatically by PIT based on the pom.xml data as follows: filter=<groupid>.<artifactid>.*. If you set it, we recommand to give the top-most package of your project. (e.g. for the test-projects it would be example.*)
- maven.localRepository: path to the local repository of Maven (.m2), if you need specific settings.
- excludedClasses: DSpot will not amplify the excluded test classes.
- additionalClasspathElements: add elements to the classpath. (e.g. a jar file)
- excludedClasses: list of full qualified name of test classes to be excluded by DSpot (see this property file)
- excludedTestCases: list of test name method to be excluded by DSpot (see this property file)

Amplifiers (-a | --amplifiers)

By default, DSpot uses no amplifier because the simplest amplification that can be done is the generation of assertions on existing tests, i.e. it will improve the oracle and the potential of the test suite to capture bugs.

However, DSpot provide different kind of Amplifier:

StringLiteralAmplifier: modifies string literals: remove, add and replace one random char, generate random string and empty string
NumberLiteralAmplifier: modifies number literals: replace by boundaries (e.g. Integer_MAX_VALUE for int), increment and decrement values
CharLiteralAmplifier: modifies char literals: replace by special chars (e.g. '\0')
BooleanLiteralAmplifier: modifies boolean literals: nagate the value
AllLiteralAmplifier: combines all literals amplifiers, i.e. StringLiteralAmplifier, NumberLiteralAmplifier, CharLiteralAmplifier and BooleanLiteralAmplifier
MethodAdd: duplicates an existing method call
MethodRemove: removes an existing method call
StatementAdd: adds a method call, and generate required parameter
ReplacementAmplifier: replaces a local variable by a generated one
TestDataMutator: old amplifier of literals (all types, deprecated)

All amplifiers are just instanciable without any parameters, e.g. new StringLiteralAmplifier.

For the amplifiers, you can give them at the constructor of your DSpot object, or use the DSpot#addAmplifier(Amplifier) method.

Test Selectors (-s | --test-criterion)

In DSpot, test selectors can be seen as a fitness: it measures the quality of amplified, and keeps only amplified tests that are worthy according to this selector.

The default selector is CloverCoverageSelector. This selector is based on OpenClover, which is a tool to compute the coverage. DSpot will keep only tests that increase the code coverage.

Following the list of avalaible test selector:

CloverCoverageSelector: uses OpenClover to compute branch coverage, and selects amplified tests that increase it.
JacocoCoverageSelector: uses JaCoCo to compute instruction coverage and executed paths (the order matters). Selects test that increase the coverage and has unique executed path.
PitMutantScoreSelector: uses PIT to computes the mutation score, and selects amplified tests that kill mutants that was not kill by the original test suite.
ExecutedMutantSelector: uses PIT to computes the number of executed mutants. It uses the number of mutants as a proxy for the instruction coverage. It selects amplfied test that execute new mutants. WARNING!! this selector takes a lot of time, and is not worth it, please look at CloverCoverageSelector or JacocoCoverageSelector.
TakeAllSelector: keeps all amplified tests not matter the quality.
ChangeDetectorSelector: runs against a second version of the same program, and selects amplified tests that fail. This selector selects only amplified test that are able to show a difference of a behavior betweeen two versions of the same program.

Selector on Diff from GitHub

DSpot can perform amplification according to a diff, from github. This is useful to enhance existing test suite on pull request for instance.

DSpot will select existing test classes according to a diff as follow:

If any test class has been modified between the two versions, DSpot selects them.
If there is not, DSpot selects test cases (and so, their test classes) according to the nem. If a test contain the name of a modified method, this test is selected.
If there is not, DSpot analyzes statical the test suite and selects test classes that invoke modified methods. The maximum number of selected test classes is the value of fr.inria.stamp.diff.SelectorOnDiff.MAX_NUMBER_TEST_CLASSES, randomly.

The requirements this feature is the following:

You must enable the mode by giving diff as value of the flag --test (-t), i.e. --test diff
You must have specify baseSha, on which DSpot must compute the diff. DSpot executes: git diff <baseSha> to find which java file has been modified. To do this, you must specify the sha in the property file, by setting the property: baseSha, e.g. baseSha=97393d96ea58110785e342fade2e054925c608ad
You must have locally both version of the program. One that you want to use amplify, and the other on which you want to compute the diff. The first is specified using the property project as explained in a classical way to amplify. The second is specified using the property folderPath.

You can specify a maximum number of selected test classes using the property maxSelectedTestClasses.

Using DSpot as an API

In this section, we explain the API of DSpot. To amplify your tests with DSpot you must do 3 steps: First of all, you have to create an InputConfiguration. Only the path to your properties is required:

// 1. Instantiate `InputConfiguration` and `InputProgram`
String propertiesFilePath = <pathToYourPropertiesFile>;
InputConfiguration inputConfiguration = new InputConfiguration(propertiesFilePath);

Then you have to build the InputProgram, this is done by attaching the InputProgram to your InputConfiguration:

InputProgram program = new InputProgram();
inputConfiguration.setInputProgram(program);

Then, you are ready to construct the DSpot object that will allow you to amplify your test. There are a lot of constructor available, all of them allow you to custom your DSpot object, and so your amplification. Following the shortest constructor with all default values of DSpot, and the longest, which allows to custom all values of DSpot:

// 2. Instantiate `DSpot` object
DSpot dspot = new DSpot(InputConfiguration);
DSpot dspot = new DSpot(
    InputConfiguration inputConfiguration, // input configuration built at step 1
    int numberOfIterations, // number of time that the main loop will be applied (-i | --iteration option of the CLI)
    List<Amplifier> amplifiers, // list of the amplifiers to be used (-a | --amplifiers option of the CLI)
    TestSelector testSelector // test selector criterion (-s | --test-selector option of the CLI)
);

Now that you have your DSpot, you will be able to amplify your tests. DSpot has several methods to amplify, but all of them starts with amplify key-word:

// 3. start ampification
dspot.amplifyTest(String regex); // will amplify all test classes that match the given regex
dspot.amplifyTest(String fulQualifiedName, List<String> testCasesName); // will amplify test cases that have their name in testCasesName in the test class fulQualifiedName
dspot.amplifyAllTests(); // will amplify all test in the test suite.

Acknowledgement

Dspot is partially funded by research project H2020 STAMP.

sbihel/dspot