Random Utils Seeding Rule

RandomUtilsSeedingRule is JUnit @Rule that allows better control of RandomUtils’ random see in unit test environments.

Note:
RandomUtilsSeedingRule supports JUnit 4 and JUnit 5 Legacy Engine. For JUnit Jupiter, use RandomUtilsSeedingExtension instead.

Creating the Rule

Like with any @Rule, the only thing you need to do in order to incorporate it in your test class is to declare a public member annotated with @Rule:

@Rule
public RandomUtilsSeedingRule rusr = new RandomUtilsSeedingRule();

Logging the Random Seed

Now that you have the RandomUtilsSeedingRule defined, your test will automagically log the random seed it uses, e.g.:

11:02:24,643 INFO  [RandomUtilsSeedingRule] Property "test.random.seed" was not set, using System.currentTimeMillis() as a seed.
11:02:24,644 INFO  [RandomUtilsSeedingRule] Running test with random seed: 1337155344644

Note that this is done using oVirt’s standard LogFactory and Log, so make sure you configure the logging in your project.

Injecting a Random Seed

Once you have a failed test due to a specific random input, you would probably want to reproduce it. This can be done by specifying the environment variable test.random.seed.

You can make sure the injection worked properly by examining the log. If, for example, you set test.random.seed=123, your output should look like this:

11:11:53,159 INFO  [RandomUtilsSeedingRule] Running test with random seed: 123