Continuous integration testing can be configured to create a build matrix to test multiple configurations of a project using a single build configuration.  This can be useful if you want to test a Grails application with multiple Grails versions, to test plugins with multiple Grails versions, or to test using varying configuration values.

The Travis CI build tool has a build matrix feature which allows you to specify multiple configuration parameters in the .travis.yml configuration file and runs the build against all possible combinations of these parameters. In the following example, I use the Groovy enVironment Manager (GVM) to change Grails versions between tests. I found this blog post which details how to set up GVM for Travis and updated this approach to force the GVM install command to return success instead of the workaround given there. The env block in the .travis.yml specifies the different environment parameters which will be passed to each test run to create the build matrix:

language: groovy

jdk:
- oraclejdk6

env:
  - GRAILS_VERSION=2.2.4
  - GRAILS_VERSION=2.2.3
  - GRAILS_VERSION=2.2.2
  - GRAILS_VERSION=2.2.1
  - GRAILS_VERSION=2.2.0

before_install:
- rm -rf ~/.gvm
- curl -s get.gvmtool.net > ~/install_gvm.sh
- chmod 775 ~/install_gvm.sh
- ~/install_gvm.sh
- echo "gvm_auto_answer=true" > ~/.gvm/etc/config
- source ~/.gvm/bin/gvm-init.sh
- gvm install grails $GRAILS_VERSION || true

branches:
  only:
    - master

script: grails clean && grails upgrade --non-interactive && grails test-app --non-interactive --stacktrace

The example build result below shows the different Grails version on the right used for each build. The source code for this example project can be found on Github.

More information about configuring a build matrix for Travis can be found in the Travis CI documentation.