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Writing Tests for a Kafka Consumer

You can accomplish a great deal by implementing your own Kafka consumers. Like almost any source code, it is a good idea to build unit tests to verify the functionality of your consumer code. Kafka's `MockConsumer` test fixture simplifies the process of building unit tests for producer code. In this lab, we will work with consumer test fixtures by writing a few unit tests for an existing consumer.

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Labs

Path Info

Level
Clock icon Intermediate
Duration
Clock icon 45m
Published
Clock icon Oct 18, 2019

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Table of Contents

  1. Challenge

    Clone the Starter Project from GitHub and Perform a Test Run

    1. Clone the starter project from GitHub:

      cd ~/
      git clone https://github.com/linuxacademy/content-ccdak-consumer-tests-lab.git
      
    2. Perform a test run to make sure the code is able to compile and run:

      cd content-ccdak-consumer-tests-lab
      ./gradlew test
      

      The code should compile, but the tests should fail since they are not implemented yet.

  2. Challenge

    Implement the Unit Tests for the `MemberSignupsConsumer`

    1. Edit the test class for MemberSignupsConsumer:

      vi src/test/java/com/linuxacademy/ccdak/consumer/MemberSignupsConsumerTest.java
      
    2. Implement the testHandleRecords_output test:

      @Test
      public void testHandleRecords_output() {
          // Verify that the testHandleRecords writes the correct data to System.out
          // A text fixture called systemOutContent has already been set up in this class to capture System.out data.
          String topic = "member_signups";
          ConsumerRecord<Integer, String> record = new ConsumerRecord<>(topic, 0, 1, 2, "ROSENBERG, WILLOW");
          Map<TopicPartition, List<ConsumerRecord<Integer, String>>> records = new LinkedHashMap<>();
          records.put(new TopicPartition(topic, 0), Arrays.asList(record));
          ConsumerRecords<Integer, String> consumerRecords = new ConsumerRecords<>(records);
      
          memberSignupsConsumer.handleRecords(consumerRecords);
          Assert.assertEquals("key=2, value=ROSENBERG, WILLOW, topic=member_signups, partition=0, offset=1\n", systemOutContent.toString());
      }
      
    3. Implement the testHandleRecords_none test:

      @Test
      public void testHandleRecords_none() {
          // Verify that testHandleRecords behaves correctly when processing no records.
          // A text fixture called systemOutContent has already been set up in this class to capture System.out data.
          String topic = "member_signups";
          Map<TopicPartition, List<ConsumerRecord<Integer, String>>> records = new LinkedHashMap<>();
          records.put(new TopicPartition(topic, 0), Arrays.asList());
          ConsumerRecords<Integer, String> consumerRecords = new ConsumerRecords<>(records);
      
          memberSignupsConsumer.handleRecords(consumerRecords);
          Assert.assertEquals("", systemOutContent.toString());
      }
      
    4. Implement the testHandleRecords_multiple test:

      @Test
      public void testHandleRecords_multiple() {
          // Verify that testHandleRecords behaves correctly when processing multiple records.
          // A text fixture called systemOutContent has already been set up in this class to capture System.out data.
          String topic = "member_signups";
          ConsumerRecord<Integer, String> record1 = new ConsumerRecord<>(topic, 0, 1, 2, "ROSENBERG, WILLOW");
          ConsumerRecord<Integer, String> record2 = new ConsumerRecord<>(topic, 3, 4, 5, "HARRIS, ALEXANDER");
          Map<TopicPartition, List<ConsumerRecord<Integer, String>>> records = new LinkedHashMap<>();
          records.put(new TopicPartition(topic, 0), Arrays.asList(record1, record2));
          ConsumerRecords<Integer, String> consumerRecords = new ConsumerRecords<>(records);
      
          memberSignupsConsumer.handleRecords(consumerRecords);
          Assert.assertEquals("key=2, value=ROSENBERG, WILLOW, topic=member_signups, partition=0, offset=1\nkey=5, value=HARRIS, ALEXANDER, topic=member_signups, partition=3, offset=4\n", systemOutContent.toString());
      }
      
    5. Run your tests and make sure they pass:

      ./gradlew test
      

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