How to write AdminCleint Mock test - junit

Question

I am using kafka and Spring and stuck to write one Junit Test case.
Following is piece of code that I want to test.
you it can be seen KafkaAdminClient.create( is static method and I am unable to mock this.
Could some suggest me how I can achieve mocking for this.
public
boolean isBrokerRunning() {
boolean isKafkaRunning = true;
try {
ListTopicsResult topics = createAdminClient().listTopics();
topics.names().get();
} catch (InterruptedException | ExecutionException e) {
isKafkaRunning = false;
}
return isKafkaRunning;
}
public AdminClient createAdminClient() {
Properties properties = new Properties();
properties.put("bootstrap.servers", bootstrapServers);
properties.put("connections.max.idle.ms", 10000);
properties.put("request.timeout.ms", 3000);
return KafkaAdminClient.create(properties);
}

Answer 1

I also faced this same issue. After spending around 2 hrs I managed to use MockAdminClient.
Just create a MockAdminClient with dummy nodes and controller.
Node controller = new Node(0, "localhost", 8121);
List<Node> brokers = Arrays.asList(
controller,
new Node(1, "localhost", 8122),
new Node(2, "localhost", 8123));
AdminClient mockAdminClient = new MockAdminClient(brokers, controller);
final NewTopic newTopic = new NewTopic("some_topic", 1, (short) 1);
mockAdminClient.createTopics(ImmutableList.of(newTopic));
assertTrue(testClass.topicExists("test_topic", mockAdminClient));

Answer 2

In case the AdminClient have to be initiated in the constructor, where AdminClient static methods have to be mocked. I did this using MockedStatic from Mockito-Inline and MockAdminClient
#BeforeEach
void setUp() {
// Creat mock Admin Client
final Node controller = new Node(0, "localhost", 8121);
final List<Node> brokers = Arrays.asList(
controller,
new Node(1, "localhost", 8122),
new Node(2, "localhost", 8123));
mockAdminClient = new MockAdminClient(brokers, controller);
try (MockedStatic<AdminClient> adminClientMockedStatic = Mockito.mockStatic(AdminClient.class)) {
adminClientMockedStatic.when(() -> AdminClient.create(anyMap())).thenReturn(mockAdminClient);
KafkaProperties kafkaProperties = new KafkaProperties();
kafkaProperties.setBootstrapServers(Arrays.asList("dummyBootstrapServer:0001"));
kafkaFacade = new KafkaFacade(kafkaProperties);
}
ReflectionTestUtils.setField(kafkaFacade, "numberOfPartition", NO_OF_PARTITIONS);
ReflectionTestUtils.setField(kafkaFacade, "retentionValue", 86400000);
ReflectionTestUtils.setField(kafkaFacade, "replicationFactor", NO_OF_REPLICAS);
ReflectionTestUtils.setField(kafkaFacade, "priority", PRIORITY);
ReflectionTestUtils.setField(kafkaFacade, "prefix", TOPIC_PREFIX);
}