Monday, April 4, 2011

JUnit testing your jBPM5 processes

Even though business processes aren't code (we even recommend you to make them as high-level as possible and to avoid adding implementation details), they also have a life cycle like other development artefacts. And since business processes can be updated dynamically, testing them (so that you don't break any use cases when doing a modification) is really important as well.

When unit testing your process, you test whether the process behaves as expected in specific use cases, for example test the output based on the existing input. To simplify unit testing, jBPM5 includes a helper class that you can use to greatly simplify your junit testing, by offering:
  • helper methods to create a new knowledge base and session for a given (set of) process(es)
    • you can select whether you want to use persistence or not
  • assert statements to check
    • the state of a process instance (active, completed, aborted)
    • which node instances are currently active
    • which nodes have been triggered (to check the path that has been followed)
    • get the value of variables
    • etc.
For example, conside the following hello world process containing a start event, a script task and an end event. The following junit test will create a new session, start the process and then verify whether the process instance completed successfully and whether these three nodes have been executed.

public class MyProcessTest extends JbpmJUnitTestCase {

public void testProcess() {
// create your session and load the given process(es)
StatefulKnowledgeSession ksession = createKnowledgeSession("sample.bpmn");
// start the process
ProcessInstance processInstance = ksession.startProcess("com.sample.bpmn.hello");
// check whether the process instance has completed successfully
assertProcessInstanceCompleted(processInstance.getId(), ksession);
// check whether the given nodes were executed during the process execution
assertNodeTriggered(processInstance.getId(), "StartProcess", "Hello", "EndProcess");

Testing processes that don't interact with the environment like this one are really easy to test but in general aren't that realistic ;) Real-life business processes typically include wait states, invocation of external services, etc. One of the advantages of our domain-specific process approach however is that you can easily specify different implementation of the node depending on the context. This means that, when you are unit testing your business process, you can register test handlers that can be used to verify whether specific services are requested correctly, and provide test responses for those services. For example, imagine you have an email node or a human task as part of your process. When unit testing, you don't want to send out an actual email but rather test whether the email that is requested contains the correct information (for example the right to email, a personalized body, etc.).

The following example describes how a process that sends out an email could be tested. This test case in particular will test whether an exception is raised when the email could not be sent (which is simulated by notifying the engine that the sending the email could not be completed). The test case uses a test handler that simply registers when an email was requested (and allows you to test the data related to the email like from, to, etc.). Once the engine has been notified the email could not be sent (using abortWorkItem(..)), the unit test verifies that the process handles this case successfully by logging this and generating an error, which aborts the process instance in this case.

public void testProcess2() {
// create your session and load the given process(es)
StatefulKnowledgeSession ksession = createKnowledgeSession("sample2.bpmn");
// register a test handler for "Email"
TestWorkItemHandler testHandler = new TestWorkItemHandler();
ksession.getWorkItemManager().registerWorkItemHandler("Email", testHandler);
// start the process
ProcessInstance processInstance = ksession.startProcess("com.sample.bpmn.hello2");
assertProcessInstanceActive(processInstance.getId(), ksession);
assertNodeTriggered(processInstance.getId(), "StartProcess", "Email");
// check whether the email has been requested
WorkItem workItem = testHandler.getWorkItem();
assertEquals("Email", workItem.getName());
assertEquals("", workItem.getParameter("From"));
assertEquals("", workItem.getParameter("To"));
// notify the engine the email has been sent
assertProcessInstanceAborted(processInstance.getId(), ksession);
assertNodeTriggered(processInstance.getId(), "Gateway", "Failed", "Error");

You can configure whether you want to execute the junit tests using persistence or not (by default using an in-memory H2 database which is started by the junit test itself and by using a history log), simply by passing a boolean whether you want to use persistence or not when calling the super constructor.

We will extend the set of out-of-the-box assert statements over time, but if you do need additional assertions for your use cases, you can already extend the set yourself by looking at the implemention of the existing ones and simply tweaking where necessary. And let us know if you create some reusable ones, we'll add them to the code base!

If you combine these test features with the advanced debugging capabilities, (as for example shown in this screencast) you can use this to walk through the process one step at a time and figure out what's happening internally. We're working on extending this even further to support full simulation and testing capabilities. This would allow you easily define and run various test scenarios, replay an execution log, etc. The foundation is already there (like a simulation clock and the definition of execution paths), but we're still working on the user interface that would make this useable by not just developers but also business users.


  1. Sweet! Nice to see testing out in front during the jBPM5 push as I am a big fan of it in BPM projects... ;-)

  2. Excellent post. I do have a question about the asserts assertProcessInstanceCompleted and assertProcessInstanceAborted.
    They seem to be identical. Is the state of a completed and aborted both null?
    // start java snippet
    public void assertProcessInstanceCompleted(long processInstanceId, StatefulKnowledgeSession ksession) {

    public void assertProcessInstanceAborted(long processInstanceId, StatefulKnowledgeSession ksession) {