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

HermesMockDefine

Is responsible for defining new topics on Hermes, provides the following methods:

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

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 avroMessagesOnTopic(String topicName, int count, Schema schema) - expects particular number of Avro messages on a given topic.

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