This section of the tutorial walks through the process of setting up Clover Test Optimization, which efficiently runs only the tests for code which has changed since the last build.
On this page:
- Adding Test Optimization tasks to build.xml
- Demonstrating that test optimization is working
- Related Links
This tutorial assumes you have completed the other Clover Tutorial steps and have fully set up Ant in
those steps to build and test the MoneyBag Java project, with Clover testing the JUnit code coverage. We
will make use of the Ant tasks set up in
build.xml from the previous tutorial chapters,
here. Knowing that, read on.
The process described here will change your build file to always run in Test Optimization mode.
Adding Test Optimization tasks to build.xml
1. Adding paths to resources
build.xml file. You should already have this line included:
from the earlier Clover-for-Ant tutorial steps. Edit around this line to add in one additional line of code, as shown below:
2. Choosing a location for the snapshot file
Test Optimization uses the concept of a 'snapshot' file. This is a file that records information about the previous build, as a point of comparison. This is what allows Clover to run Optimized tests, by comparing the data in the snapshot file with the current build that you are intending to launch.
For the purposes of this tutorial, leave the snapshot file in its default location, (next to the
clover.db ) here:
3. Adding a new Ant target to generate the optimized test 'snapshot'
Now' we'll and a new Ant target to generate the test snapshot:
4. Editing the JUnit task to add the 'clover-optimized-testset' element
build.xml file, edit the
test target ,specifically the
junit portion and its sub-element,
batchtest. Your code inside
batchtest will look like so:
To add Test Optimization to the build: add a new element,
clover-optimized-testset, move the
fileset element inside the new
clover-optimized-testset element. Edit your
batchtest code block until it is the same as
Your Test Optimization configuration is now complete.
Demonstrating that test optimization is working
Finally, we will build our project, creating the essential Clover 'snapshot' file. Next, we will edit one of the Java files in the 'Money' project, commenting out one of the unit tests. When we run the Test Optimized build a second time, Clover will compare the snapshot file against the new coverage database and then run targeted tests which incorporate only those files which have changed, (which in this case will be only one, the Java file that we edited). This saves valuable time, which is the key advantage of Test Optimization.
5. Running the test optimized build
Run your build with the following command:
clover.snapshot target here will create the additional snapshot database,
which is used as a point of comparison for the Test Optimization. This is essential for enabling Test
Optimization of future builds.
Clover will output this text to the console, showing that it has created the all-important snapshot file:
6. Running an 'empty' optimized build
If we re-run the same Ant build, Clover will detect that none of the source files have changed. Because we are running a Test Optimized build, Clover won't build or test anything, the result is zero tests.
With a Test-Optimized build, Clover will output the following if no files have changed since the last build:
This is desired behavior, especially in a continuous integration environment where builds are automated and run regularly.
7. Editing a file in the project
To show how Test Optimization works, we'll change one of the files in the project. When we run the Test Optimized build, Clover will detect that this file has changed and build it exclusively (rather than rebuilding everything).
Edit the file
MoneyBag.java from the tutorial project. For the purposes of this
demonstration, add a
System.out.println() in the
add method on line #27:
Now save the file.
8. Rebuilding the project with test optimization
Now having changed a file in the project, we will run the same Ant tasks again.
Clover will detect that the source file has changed, rebuilding and only running the tests for that file specifically. We can see this illustrated in the console output:
This Clover output shows that only one of two test classes was included. Note that all the test methods in this one test class were run, since Clover currently optimizes to the class level only. Clover also estimates the time saved in this particular build and test run. In this case the saving is only seconds, but in more complex projects it could well be multiple minutes or hours.
That concludes the Clover-for-Ant Test Optimization tutorial. For more information on integrating Test Optimization, see the related links below.