The TestUtils class is mostly used for properties assertions in JUnit tests:

@Test
public void loadBalancerRef() {
    MessageChannel channel = channels.get("lbRefChannel");
    LoadBalancingStrategy lbStrategy = TestUtils.getPropertyValue(channel,
                 "dispatcher.loadBalancingStrategy", LoadBalancingStrategy.class);
    assertTrue(lbStrategy instanceof SampleLoadBalancingStrategy);
}

TestUtils.getPropertyValue() is based on Spring’s DirectFieldAccessor and provides the ability to get a value from the target private property. As you see by the example above it also supports nested properties access, using dotted notation.

The createTestApplicationContext() factory method produce a TestApplicationContext instance with the supplied Spring Integration environment.

See the JavaDocs of other TestUtils methods for more information about this class.

The SocketUtils provides several methods to select a random port(s) for exposing server-side components without conflicts:

<bean id="socketUtils" class="org.springframework.integration.test.util.SocketUtils" />

<int-syslog:inbound-channel-adapter id="syslog"
            channel="sysLogs"
            port="#{socketUtils.findAvailableUdpSocket(1514)}" />

<int:channel id="sysLogs">
    <int:queue/>
</int:channel>

Which is used from the unit test as:

@Autowired @Qualifier("syslog.adapter")
private UdpSyslogReceivingChannelAdapter adapter;

@Autowired
private PollableChannel sysLogs;
...
@Test
public void testSimplestUdp() throws Exception {
    int port = TestUtils.getPropertyValue(adapter1, "udpAdapter.port", Integer.class);
    byte[] buf = "<157>JUL 26 22:08:35 WEBERN TESTING[70729]: TEST SYSLOG MESSAGE".getBytes("UTF-8");
    DatagramPacket packet = new DatagramPacket(buf, buf.length,
                              new InetSocketAddress("localhost", port));
    DatagramSocket socket = new DatagramSocket();
    socket.send(packet);
    socket.close();
    Message<?> message = foo.receive(10000);
    assertNotNull(message);
}

	Note
	This tecnique is not foolproof; some other process could be allocated the "free" port before your test opens it. It is generally more preferable to use a server port 0 and let the operating system select the port for you, then discover the selected port in your test. We have converted most framework tests to use this preferred technique.

The OnlyOnceTrigger is useful for polling endpoints when it is good to produce only one test message and verify the behavior without impacting of unexpected other period messages:

<bean id="testTrigger" class="org.springframework.integration.test.util.OnlyOnceTrigger" />

<int:poller id="jpaPoller" trigger="testTrigger">
    <int:transactional transaction-manager="transactionManager" />
</int:poller>

@Autowired
@Qualifier("jpaPoller")
PollerMetadata poller;

@Autowired
OnlyOnceTrigger testTrigger;
...
@Test
@DirtiesContext
public void testWithEntityClass() throws Exception {
    this.testTrigger.reset();
    ...
    JpaPollingChannelAdapter jpaPollingChannelAdapter = new JpaPollingChannelAdapter(jpaExecutor);

    SourcePollingChannelAdapter adapter = JpaTestUtils.getSourcePollingChannelAdapter(
    		jpaPollingChannelAdapter, this.outputChannel, this.poller, this.context,
    		this.getClass().getClassLoader());
    adapter.start();
    ...
}

The org.springframework.integration.test.support package contains various abstract classes which should be implemented in target tests. See their JavaDocs for more information.

The org.springframework.integration.test.matcher package contains several Matcher implementations to assert Message and its properties in unit tests:

import static org.springframework.integration.test.matcher.PayloadMatcher.hasPayload;
...
@Test
public void transform_withFilePayload_convertedToByteArray() throws Exception {
    Message<?> result = this.transformer.transform(message);
    assertThat(result, is(notNullValue()));
    assertThat(result, hasPayload(is(instanceOf(byte[].class))));
    assertThat(result, hasPayload(SAMPLE_CONTENT.getBytes(DEFAULT_ENCODING)));
}

The MockitoMessageMatchers factory can be used for mocks stubbing and verifications:

static final Date SOME_PAYLOAD = new Date();

static final String SOME_HEADER_VALUE = "bar";

static final String SOME_HEADER_KEY = "test.foo";
...
Message<?> message = MessageBuilder.withPayload(SOME_PAYLOAD)
                .setHeader(SOME_HEADER_KEY, SOME_HEADER_VALUE)
                .build();
MessageHandler handler = mock(MessageHandler.class);
handler.handleMessage(message);
verify(handler).handleMessage(messageWithPayload(SOME_PAYLOAD));
verify(handler).handleMessage(messageWithPayload(is(instanceOf(Date.class))));
...
MessageChannel channel = mock(MessageChannel.class);
when(channel.send(messageWithHeaderEntry(SOME_HEADER_KEY, is(instanceOf(Short.class)))))
        .thenReturn(true);
assertThat(channel.send(message), is(false));

Additional utilities will eventually be added or migrated. For example RemoteFileTestSupport implementations for the (S)FTP tests can be moved from the test directory of those particular modules to this spring-integration-test-support artifact.

The MockIntegration factory provides an API to build mocks for Spring Integration beans which are parts of the integration flow - MessageSource, MessageProducer, MessageHandler, MessageChannel. The target mocks can be used during configuration phase:

<int:inbound-channel-adapter id="inboundChannelAdapter" channel="results">
    <bean class="org.springframework.integration.test.mock.MockIntegration" factory-method="mockMessageSource">
        <constructor-arg value="a"/>
        <constructor-arg>
            <array>
                <value>b</value>
                <value>c</value>
            </array>
        </constructor-arg>
    </bean>
</int:inbound-channel-adapter>

@InboundChannelAdapter(channel = "results")
@Bean
public MessageSource<Integer> testingMessageSource() {
    return MockIntegration.mockMessageSource(1, 2, 3);
}
...
StandardIntegrationFlow flow = IntegrationFlows
        .from(MockIntegration.mockMessageSource("foo", "bar", "baz"))
        .<String, String>transform(String::toUpperCase)
        .channel(out)
        .get();
IntegrationFlowRegistration registration = this.integrationFlowContext.registration(flow)
        .register();

as well as in the target test method to replace the real endpoints before performing verifications and assertions. For this purpose, the aforementioned MockIntegrationContext should be used from the test:

this.mockIntegrationContext.instead("mySourceEndpoint",
        MockIntegration.mockMessageSource("foo", "bar", "baz"));
Message<?> receive = this.results.receive(10_000);
assertNotNull(receive);
assertEquals("FOO", receive.getPayload());