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# Tests

There are two approaches for testing: Unit tests and integration tests.

Integration tests start up parts of the openHAB framework and the test is performed with real OSGi services. Tests of this kind should be used rarely as they increase the overall test runtime considerably. But it usually makes sense to have at least one integration test for a complex extension, to make sure everything (all your OSGi services) start up correctly.

# Unit tests

Each class inside the src/test folder will have all public methods with a @Test annotation automatically executed as a test. Inside the class one can refer to all classes from the host bundle and all imported classes.

The following code snippet shows a simple JUnit test which tests the toString conversation of a PercentType.

public class PercentTypeTest {
    public void DoubleValue() {
        PercentType pt = new PercentType("0.0001");
        assertEquals("0.0001", pt.toString());

Using the hamcrest matcher library (opens new window) is a good way to write expressive assertions. In contrast to the original assertion statements from JUnit the hamcrest matcher library allows to define the assertion in a more natural order:

PercentType pt = new PercentType("0.0001");
assertThat(pt.toString(), is(equalTo("0.0001")));

# Mockito

In order to keep tests as focused as possible we use the mocking framework [ (opens new window) Mockito]. Mockito lets us verify interactions between supporting classes and the unit under test and additionally supports stubbing of method calls for these classes. Please read the very short but expressive introduction on the [ (opens new window) Mockito homepage] in addition to this small example:

public class MyBindingHandlerTest {

    private ThingHandler handler;

    private @Mock ThingHandlerCallback callbackMock;
    private @Mock Thing thingMock;

    public void setUp() {
        handler = new MyBindingHandler(thingMock);

    public void tearDown() {
        // Free any resources, like open database connections, files etc.

    public void initializeShouldCallTheCallback() {
        // we expect the handler#initialize method to call the callbackMock during execution and
        // pass it the thingMock and a ThingStatusInfo object containing the ThingStatus of the thingMock.

        // verify the interaction with the callbackMock.
        // Check that the ThingStatusInfo given as second parameter to the callbackMock was build with the ONLINE status:
        verify(callbackMock).statusUpdated(eq(thingMock), argThat(arg -> arg.getStatus().equals(ThingStatus.ONLINE)));


# Assertions

Here is small example on when to use Hamcrest or JUnit assertions. In general Hamcrest should be favoured over JUnit as for the more advanced and detailed error output:

import static org.hamcrest.CoreMatchers.*;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
import static org.junit.jupiter.api.Assertions.*;

import java.util.List;

import org.junit.jupiter.api.Test;


public void assertionsToBeUsed() {
    // use JUnit assertions for very basic checks:
    assertNotNull(new Object());

    boolean booleanValue = true;
    assertTrue(booleanValue); // test boolean values only, no conditions or constraints

    // use Hamcrest assertions for everything else:
    assertThat("myString", is("myString"));
    assertThat("myString", is(instanceOf(String.class)));
    assertThat("myString", containsString("yS"));
    assertThat(List.of("one", "two"), hasItem("two"));
    assertThat(List.of("one", "two"), hasSize(2));

    // also valuable for null/boolean checks as the error output is advanced:
    assertThat(null, is(nullValue()));
    assertThat(new Object(), is(not(nullValue())));
    assertThat(true, is(not(false)));

# Integration tests

Some components of openHAB are heavily bound to the OSGi runtime, because they use OSGi core services like the EventAdmin or the ConfigurationAdmin or the ItemRegistry That makes it hard to test those components outside of the OSGi container.

Integration tests allow to run test classes that extend JavaOSGiTest inside an OSGi runtime. They reside as separate bundles in the itests/ directory. A .bndrun file must be provided with your integration test to configure the runtime.

Those kind of tests should be used sparingly as the setup is more complex and introduces execution overhead. Most situations can be tested using mocks (see Mockito) and unit tests.

From Maven one can execute the test with mvn install command from the folder of the test fragment bundle.

# Example

The base class JavaOSGiTest sets up a bundle context and has convenience methods for registering mocks as OSGi services and the retrieval of registered OSGi services. Public methods with a @Test annotation will automatically be executed as OSGi tests, as long as the class-name ends with Test. The following JUnit/Mockito test class shows how to test the ItemRegistry by providing a mocked ItemProvider.

import static org.hamcrest.CoreMatchers.*;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.collection.IsCollectionWithSize.hasSize;
import static org.mockito.Mockito.when;

import java.util.List;

import org.eclipse.jdt.annotation.NonNullByDefault;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;
import org.openhab.core.items.Item;
import org.openhab.core.items.ItemProvider;
import org.openhab.core.items.ItemRegistry;
import org.openhab.core.library.items.SwitchItem;

public class JavaItemRegistryOSGiTest extends JavaOSGiTest {

    private static final String ITEM_NAME = "switchItem";

    private @Mock @NonNullByDefault({}) ItemProvider itemProviderMock;

    private @NonNullByDefault({}) ItemRegistry itemRegistry;

    public void setUp() {
        itemRegistry = getService(ItemRegistry.class);
        when(itemProviderMock.getAll()).thenReturn(List.of(new SwitchItem(ITEM_NAME)));

    public void getItemsShouldReturnItemsFromRegisteredItemProvider() {
        assertThat(itemRegistry.getItems(), hasSize(0));


        List<Item> items = List.copyOf(itemRegistry.getItems());
        assertThat(items, hasSize(1));
        assertThat(items.get(0).getName(), is(equalTo(ITEM_NAME)));


        assertThat(itemRegistry.getItems(), hasSize(0));

Mocks annotated with @Mock are automatically created and injected into the class when annotating a class with @ExtendWith(MockitoExtension.class). In the setUp method the ItemRegistry OSGi service is retrieved through the method getService from the base class OSGiTest and assigned to a private variable. Then the ItemProvider mock is configured to return a list with one SwitchItem when itemProviderMock.getAll gets called. The test method first checks that the registry delivers no items by default. Afterwards it registers the mocked ItemProvider as OSGi service with the method registerService and checks if the ItemRegistry returns one item now. At the end the mock is unregistered again.

# Common errors

# Failed to execute goal org.eclipse.tycho:tycho-surefire-plugin:XXX:test (default-test) on project XXX: No tests found

Maven might report this error when building your project, it means that the Maven surefire plugin cannot find any tests to execute, please check the following details:

  • Did you add any test classes with a class-name which ends with Test (singular)
  • Did you annotate any methods with @Test