Hermes Mock

A thin library designed to mocking Hermes Frontend in tests.

Overview

Mocking is provided by HermesMock class, which consists of 3 parts: - HermesMockDefine - HermesMockExpect - HermesMockQuery

HermesMock

<T> void resetReceivedAvroRequests(String topicName, Schema schema, Class<T> clazz, Predicate<T> predicate) - resets requests received by Avro topic matching given predicate
<T> void resetReceivedJsonRequests(String topicName, Class<T> clazz, Predicate<T> predicate) - resets requests received by Json topic matching given predicate

HermesMockDefine

Is responsible for defining new topics on Hermes, provides the following methods. Both jsonTopic and avroTopic methods return an StubMapping object:

jsonTopic(String topicName) - defines a JSON topic.
avroTopic(String topicName) - defines an Avro topic.
jsonTopic(String topicName, int statusCode) - defines a JSON topic that when published on responds with a given response code.
avroTopic(String topicName, int statusCode) - defines an Avro topic that when published on responds with a given response code.
jsonTopic(String topicName, Response response) - defines a JSON topic that when published on responds with a given response.
avroTopic(String topicName, Response response) - defines an Avro topic that when published on responds with a given response.
avroTopic(String topicName, Response response, Schema schema, Class<T> clazz, Predicate<T> predicate) - defines an Avro topic with predicate to match request by field in schema
jsonTopic(String topicName, Response response, Class<T> clazz, Predicate<T> predicate) - defines a Json topic with predicate to match request by field
removeStubMapping(StubMapping stubMapping) - removes defined stub mapping

Response allows to define the following elements: - statusCode - a HTTP response code - fixedDelay - a response will be returned after the given time

HermesMockExpect

Is responsible for expectation of message on Hermes side, provides the following methods:

void singleMessageOnTopic(String topicName) - expects 1 and only 1 message on topic.
<T> void singleJsonMessageOnTopicAs(String topicName, Class<T> clazz) - expects 1 and only 1 JSON message on a topic of a specific type.
<T> void singleAvroMessageOnTopic(String topicName, Schema schema) - expects 1 and only 1 Avro message on a topic of a specific type.
void messagesOnTopic(String topicName, int count) - expects particular number of messages on a given topic.
<T> void jsonMessagesOnTopicAs(String topicName, int count, Class<T> clazz) - expects particular number of JSON messages on a given topic.
<T> void jsonMessagesOnTopicAs(String topicName, int count, Class<T> clazz, Predicate<T> predicate) - expects particular number of JSON messages on a given topic and matching given predicate.
<T> void avroMessagesOnTopic(String topicName, int count, Schema schema) - expects particular number of Avro messages on a given topic.
<T> void avroMessagesOnTopic(String topicName, int count, Schema schema, Class<T> clazz, Predicate<T> predicate) - expects particular number of Avro messages on a given topic and matching given predicate.

HermesMockQuery

Is responsible for querying Hermes for a received messages, provides the following methods:

List<Request> allRequests() - get all the received messages.
List<Request> allRequestsOnTopic(String topicName) - get all the received messages on a given topic.
<T> List<T> allJsonMessagesAs(String topicName, Class<T> clazz) - get all the received messages on a given topic.
List<byte[]> allAvroRawMessages(String topicName) - get all the received raw Avro messages on a given topic.
<T> List<T> allAvroMessagesAs(String topicName, Schema schema, Class<T> clazz) - get all the received Avro messages on a given topic as a specific type.
Optional<Request> lastRequest(String topicName) - get last received request on topic.
<T> Optional<T> lastJsonMessageAs(String topicName, Class<T> clazz) - get last received JSON message on topic as a specific type.
<T> Optional<byte[]> lastAvroRawMessage(String topicName) - get last received raw Avro message on topic.
<T> Optional<T> lastAvroMessageAs(String topicName, Schema schema, Class<T> clazz) - get last received Avro message on topic as a specific type.

Creating

To start using Hermes mock, add it as a dependency:

testImplementation group: 'pl.allegro.tech.hermes', name: 'hermes-mock', version: versions.hermes

Example

class MyServiceTest {

    @Rule
    HermesMockRule hermesMock = new HermesMockRule(8090);

    @Test
    public void exampleTest() {
        // given
        MyMessage myMessage = new MyMessage("id123", "content");
        String topicName = "myTopic";

        hermesMock.define().jsonTopic(topicName);

        // when
        myService.publishHermesMessage(myMessage);

        // then
        hermesMock.expect().singleJsonMessageOnTopicAs(topicName, MyMessage.class);

        // and
        List<MyMessage> all = hermesMock.query().allJsonMessagesAs(topicName, MyMessage.class);

        // and verify that `all` contains what we're expecting 
    }
}

JUnit5 / Spock2 automatic startup issues

If you're using JUnit5 or Spock2 HermesMockRule won't start automatically in your tests. In order to make it work you can:

Start and stop Hermes mock manually using HermesMock:

class Junit5Test {

    private HermesMock hermesMock = new HermesMock.Builder().withPort(8090).build();

    @BeforeAll
    static void setup() {
        hermesMock.start();
    }

    @AfterAll
    static void cleanup() {
        hermesMock.stop();
    }

    @Test
    public void exampleTest() {
        // you can now use Hermes mock as in previous example
    }
}

(Only for Spock2) add spock-junit4 dependency which allows usage of JUnit4 annotations in Spock2, so you can use HermesMockRule as shown earlier.

testImplementation group: 'org.spockframework', name: 'spock-junit4', version: versions.spock