Technical News

Nov 08 2017

Flaky tests handling with Jenkins and JIRA

Flaky tests are a plague because they lower the credibility in your CI strategy, by sending false positive notification emails.

Vincent Massol, XWiki Technical Director suggests a new Flaky test strategy.

Oct 29 2017

Creating your own project's Quality Dashboard

SoftShake 2017, Geneva

Offered at SoftShake 2017 in Geneva, by Vincent Massol, Technical Director of XWiki SAS, this brand new presentation explains how to use XWiki to create a custom Quality Dashboard by aggregating metrics from other sites (Jenkins, SonarQube, JIRA and GitHub), saving them locally to draw history graphs and sending emails when combined metric thresholds are crossed. 

Sep 28 2017

Mutation testing with PIT and Descartes

Vincent Massol, Technical Director of XWiki SAS, wrote an article about a recent experimentation with Descartes, a mutation engine for PIT, in the framework of the STAMP project. 

Here's an example of running Descartes on an XWiki module:

For more information, click on the Pit test report and read the Vincent Massol blog post, published here: Mutation testing with PIT and Descartes

Sep 17 2017

Using Docker and Jenkins to test configurations

XWiki SAS is part of the STAMP research project and one domain of this research is improving configuration testing.

In this article, Vincent Massol, Technical Director of XWiki SAS, suggests a new architecture that should allow XWiki to be tested on various configurations, including various supported databases and versions, various Servlet containers and versions, and Various Browsers and versions.

Aug 30 2017

Mutate and Test Your Tests

by Benoit Baudry

I am extremely proud and happy that my talk on mutation testing got accepted as an early bird for EclipseCon Europe 2017.

We will talk a lot about software testing at the project quality day. In this talk, I will focus on qualitative evaluation of a unit test suite. Statement coverage is commonly used to quantify the quality of a test suite: it measures the ratio of source code statements that are executed at least once when running the test suite. However, statement coverage is known to be a rather weak quality indicator. For example, a test suite that covers 100% of the statements and that has absolutely no assertion is a very bad test suite, yet is considered of excellent quality according statement coverage.

Mutation testing is another way of evaluating the quality of a test suite, according to the following intuition: a test suite is good to test a specific program if it is able to detect bugs in this program: so, let's inject bugs in this program and see how much the test suite is able to detect. Mutation testing was proposed back at the end of the 1970's by Richard A. DeMillo, Richard J. Lipton, and Fred G. Sayward, and their idea was quite simple: create multiple mutants of the program under test, i.e., versions of the program with one seeded bug (for example, on off by one error), run the test suite against each mutant, and see how many are detected. Since then, many tools were built for mutation testing, including PIT, a state of the art tool for Java mutation testing.

Considering the example below, PIT will generate one mutant in which the == operand at line 2 is replaced by !=, a mutant in which the return value.hashcode() at line 11 is replaced by return 0, and so on.

public int hashCode() {
    if (value == null) {return 31;}
    if (isIntegral(this)) {
        long value = getAsNumber().longValue();
        return (int) (value ^ (value >>> 32));
    if (value instanceof Number) {
        long value = Double.doubleToLongBits(getAsNumber().doubleValue());
        return (int) (value ^ (value >>> 32));
    return value.hashCode();

Mutation testing tools generate a large quantities of mutants, and, consequently, the analysis takes a long time to run. In this talk, I will present Descartes: a mutation testing tool that adapts PIT for extreme mutation. Descartes follows the principle of mutation testing, but generates mutants by removing completely the body of a method, instead of injecting multiple small bugs. For example, Descartes generates only two mutants for the 'hashCode()' above:

public int hashCode() {
    return 0;

public int hashCode() {
    return 1;

In this talk, I will summarize the principles of mutation testing, current state of the art and then will illustrate how it can work with PIT and Descartes. I will conclude with some of the lessons we have learned when running Descartes on open source projects.

About the author

Benoit Baudry is a Professor at the KTH Royal Institute of Technology in Stockholm, Sweden. He currently investigates novel techniques for automatic test amplification in DevOps. His research focuses on program analysis, transformation, testing and diversification. Until August 2017 he was a research scientist at INRIA, France, where he led the DiverSE research group (EPI) since 2013.

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