Zeebe Process Test

This project allows you to unit test your Camunda Platform 8 BPMN processes. It will start a Zeebe test engine and provide you with a set of assertions you can use to verify your process behaves as expected.

Prerequisites

• Java 17+ when running with an embedded engine (zeebe-process-test-extension)
• Java 8+ and Docker when running using testcontainers (zeebe-process-test-extension-testcontainer)
• JUnit 5

NOTE: If you use Spring and want to write tests, please use spring-zeebe-test as a wrapper around Zeebe Process Test to hook everything into the Spring lifecycle. See Spring Zeebe: Writing test cases for details.

Getting Started

Dependency

Zeepe Process Test provides you with two dependencies. Which one you need to use is dependent on the Java version you are using.

Embedded (JDK 17+)

If you are building your project with JDK 17+ you can make use of an embedded Zeebe test engine. The advantage of using this instead of the testcontainer version is that this is the faster solution. This also does not require Docker to be running. There is also a downside to this solution. The JDK requirement is bound to the Java version of the Zeebe engine. Whenever this Java version changes, you'd either have to switch to the testcontainer version, or upgrade your own JDK to match Zeebe engine.

<dependency>
  <groupId>io.camunda</groupId>
  <artifactId>zeebe-process-test-extension</artifactId>
  <version>X.Y.Z</version>
  <scope>test</scope>
</dependency>

Testcontainers (JDK 8+)

If you are building your project with a JDK that's lower than 17 you need to use this dependency. It starts a testcontainer in which a Zeebe test engine is running. The advantage of using this version instead of the embedded version is that your code can be implemented independently of the Java version that is used by the Zeebe engine. This has some downsides: Testcontainers provide some overhead, which means tests will be slower. There is also the extra requirement that Docker must be running to execute the tests.

<dependency>
  <groupId>io.camunda</groupId>
  <artifactId>zeebe-process-test-extension-testcontainer</artifactId>
  <version>X.Y.Z</version>
  <scope>test</scope>
</dependency>

Using Maven profiles you can also switch the test dependencies based on the available Java version.

Spring support

If you use the Spring framework or Spring Boot and you want to write tests, please use spring-zeebe-test as a wrapper around this library. This will hook everything into the Spring lifecycle. See Spring Zeebe: Writing test cases for details.

Annotation

Annotate your test class with the @ZeebeProcessTest annotation. This annotation will do a couple of things:

1. It will manage the lifecycle of the testcontainer / embedded test engine
2. It will create a client which can be used to interact with the engine.
3. It will (optionally) inject 3 fields in your test class:
   1. ZeebeTestEngine - This is the engine that will run your process. It will provide some basic functionality to help you write your tests, such as waiting for an idle state and increasing the time.
   2. ZeebeClient - This is the client that allows you to send commands to the engine, such as starting a process instance. The interface of this client is identical to the interface you use to connect to a real Zeebe engine.
   3. RecordStream - This gives you access to all the records that are processed by the engine. Assertions use the records for verifying expectations. This grants you the freedom to create your own assertions.

Example:

// When using the embedded test engine (Java 17+)
import io.camunda.zeebe.process.test.extension.ZeebeProcessTest;

// When using testcontainers (Java 8+)
import io.camunda.zeebe.process.test.extension.testcontainer.ZeebeProcessTest;

@ZeebeProcessTest
class DeploymentAssertTest {
  private ZeebeTestEngine engine;
  private ZeebeClient client;
  private RecordStream recordStream;
}

Switching between testcontainers and embedded

Switching between testcontainers and embedded is very easy to do. You'll have to take two steps:

1. Switch to the relevant dependency

• Testcontainers: zeebe-process-test-extension-testcontainer
• Embedded: zeebe-process-test-extension

2. Change the import of @ZeebeProcessTest

• Testcontainers: import io.camunda.zeebe.process.test.extension.testcontainer.ZeebeProcessTest;
• Embedded: import io.camunda.zeebe.process.test.extension.ZeebeProcessTest;

Assertions

There are multiple entrypoints for starting assertions:

Deployment Assertions

DeploymentEvent event = client.newDeployCommand()
  .addResourceFromClasspath("my-process.bpmn")
  .send()
  .join();
DeploymentAssert assertions = BpmnAssert.assertThat(event);

Process Instance Assertions

Started by manually sending an event:

ProcessInstanceEvent event = client.newCreateInstanceCommand()
  .bpmnProcessId("<processId>")
  .latestVersion()
  .send()
  .join();
ProcessInstanceAssert assertions = BpmnAssert.assertThat(event);

ProcessInstanceResult event = client.newCreateInstanceCommand()
  .bpmnProcessId("<processId>")
  .latestVersion()
  .withResult()
  .send()
  .join();
  ProcessInstanceAssert assertions = BpmnAssert.assertThat(event);

Started by a timer:

Optional<InspectedProcessInstance> firstProcessInstance = InspectionUtility.findProcessEvents()
  .triggeredByTimer(ProcessPackTimerStartEvent.TIMER_ID)
  .findFirstProcessInstance();
ProcessInstanceAssert assertions = BpmnAssert.assertThat(firstProcessInstance.get());

Started by a call activity:

Optional<InspectedProcessInstance> firstProcessInstance = InspectionUtility.findProcessInstances()
  .withParentProcessInstanceKey(<key>)
  .withBpmnProcessId("<called process id>")
  .findFirstProcessInstance();
ProcessInstanceAssert assertions = BpmnAssert.assertThat(firstProcessInstance.get());

Job Assertions

ActivateJobsResponse response = client.newActivateJobsCommand()
  .jobType("<jobType>")
  .maxJobsToActivate(1)
  .send()
  .join();
ActivatedJob activatedJob = response.getJobs().get(0);
JobAssert assertions = BpmnAssert.assertThat(activatedJob);

Message Assertions

PublishMessageResponse response = client
  .newPublishMessageCommand()
  .messageName("<messageName>")
  .correlationKey("<correlationKey>")
  .send()
  .join();
MessageAssert assertions = BpmnAssert.assertThat(response);

Incident Assertions

Via a process instance

ProcessInstanceEvent event = client.newCreateInstanceCommand()
  .bpmnProcessId("<processId>")
  .latestVersion()
  .send()
  .join();
IncidentAssert assertions = BpmnAssert.assertThat(event)
  .extractingLatestIncident();

Via a job:

ActivateJobsResponse response = client.newActivateJobsCommand()
  .jobType("<jobType>")
  .maxJobsToActivate(1)
  .send()
  .join();
ActivatedJob activatedJob = response.getJobs().get(0);
IncidentAssert assertions = BpmnAssert.assertThat(activatedJob)
  .extractingLatestIncident();

Waiting for idle and busy state

Wait for idle state

Warning! Waiting for idle state is a new feature. When the engine is detected to be idle it will wait 30ms before checking again. If it is still idle at that stage it is considered to be in an idle state.

We do not know if the 30ms delay is sufficient. Using it could result in flaky tests!

Any feedback about the wait for idle state is highly appreciated! Please let us know if the delay should be higher, or configurable.

engine.waitForIdleState(timeout) will cause your test to stop executing until the engine has reached an idle state. If the engine does not reach an idle state within the specified timeout a TimeoutException will be thrown.

We have defined an idle state as a state in which the engine makes no progress and is waiting for new commands or events to trigger. Once the engine has detected it has become idle it will wait for a delay (30ms) and check if it is still idle. If this is the case it is considered to be in idle state and continue your test.

Wait for busy state

engine.waitForBusyState(timeout) will cause your test to stop executing until the engine has reached a busy state. If the engine does not reach a busy state within the specified timeout a TimeoutException will be thrown.

We consider the engine to have reached a busy state when any new record / command is processed since we've started waiting.

Waiting for a busy state is useful in scenarios where you're expecting the engine to start doing something, without explicitly triggering it yourself. An example of this would be a process with a timer event. We can increase the time of the engine, but we cannot trigger the timer explicitly. Because of this we should wait for a busy state after increasing the engine time.

Examples

Examples

Engine lifecycle

The lifecycle of the engine will be fully managed by the extension. The lifecycle for both extensions differs slightly.

Testcontainers

1. Before the test suite start the testcontainer
2. Before each test stop the current Zeebe test engine (if applicable) and create a new Zeebe test engine for the next test
3. Run the test
4. After the test suite stop the testcontainer

Embedded

1. Before each test create a new Zeebe test engine
2. Run the test
3. After each test stop the Zeebe test engine

Project Structure

The project consists of 5 different modules:

1. Api (api)

• This module contains public interfaces. It should always be Java 8 compatible.

2. Assertions (assertions)

• This module contains all the assertions. It should always be Java 8 compatible.

3. Engine (engine)

• This module contains the in memory engine. It is not bound to a specific Java version. Therefore, it is not recommended to depend on this module.

4. Engine agent (engine-agent)

• This module is a wrapper around the engine. It enables running the engine in a docker container.

5. Engine protocol (engine-protocol)

• This module defines the gRPC protocol used for communicating with the engine agent.

6. Extension (extension)

• This module contains the extension for using the embedded test engine.

7. Extension testcontainer (extension-testcontainer)

• This module contains the extension for using the test engine in a testcontainer.

8. Filters (filters)

• This module contains filters that can be used to filter a list of Zeebe records.

9. QA (qa)

• This module contains our QA tests. There is no reason to depend on this module. It is not bound to a specific Java version.

Backwards compatibility

Starting from release 1.4.0 we will ensure backwards compatibility in this project. This will be limited to the extension, the assertions and the public interfaces. We will aim to be backwards compatible on other modules, however this is not guaranteed. Using / extending these are at your own risk.

Contributing

Please refer to the Contributions Guide.

Credits

Special thanks to the creators of the Embedded Zeebe Engine and Camunda BPMN Assert. This project was heavily inspired by these solutions.

License

Zeebe Process Test source files are made available under the Apache License, Version 2.0 except for the parts listed below, which are made available under the Zeebe Community License, Version 1.1.

Available under the Zeebe Community License, Version 1.1:

• Engine (engine)
• Engine Agent (engine-agent)
• Extension (extension)