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Writing Tests for a Kafka Producer

Unit testing is an important part of developing software with good practices, and this even applies to your custom Kafka producer code. Luckily, Kafka offers test fixtures that can help you easily write such tests for your Kafka producers. In this lab, we will work with Kafka's producer test fixtures by building a few unit tests for some existing producer code.

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Path Info

Clock icon Intermediate
Clock icon 45m
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
    2. Perform a test run to make sure the code is able to compile and run:

      cd content-ccdak-producer-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 `MemberSignupsProducer`

    1. Edit the test class for MemberSignupsProducer:

      vi src/test/java/com/linuxacademy/ccdak/producer/
    2. Implement the testHandleMemberSignup_sent_data test:

      public void testHandleMemberSignup_sent_data() {
          // Perform a simple test to verify that the producer sends the correct data to the correct topic when handleMemberSignup is called.
          // Verify that the published record has the memberId as the key and the uppercased name as the value.
          // Verify that the records is sent to the member_signups topic.
          memberSignupsProducer.handleMemberSignup(1, "Summers, Buffy");
          List<ProducerRecord<Integer, String>> records = mockProducer.history();
          Assert.assertEquals(1, records.size());
          ProducerRecord<Integer, String> record = records.get(0);
          Assert.assertEquals(Integer.valueOf(1), record.key());
          Assert.assertEquals("SUMMERS, BUFFY", record.value());
          Assert.assertEquals("member_signups", record.topic());    
    3. Implement the testHandleMemberSignup_partitioning test:

      public void testHandleMemberSignup_partitioning() {
          // Verify that records with a value starting with A-M are assigned to partition 0, and that others are assigned to partition 1.
          // You can send two records in this test, one with a value that begins with A-M and the other that begins with N-Z.
          memberSignupsProducer.handleMemberSignup(1, "M");
          memberSignupsProducer.handleMemberSignup(1, "N");
          List<ProducerRecord<Integer, String>> records = mockProducer.history();
          Assert.assertEquals(2, records.size());
          ProducerRecord<Integer, String> record1 = records.get(0);
          Assert.assertEquals(Integer.valueOf(0), record1.partition());
          ProducerRecord<Integer, String> record2 = records.get(1);
          Assert.assertEquals(Integer.valueOf(1), record2.partition());
    4. Implement the testHandleMemberSignup_output test:

      public void testHandleMemberSignup_output() {
          // Verify that the producer logs the record data to System.out.
          // A text fixture called systemOutContent has already been set up in this class to capture System.out data.
          memberSignupsProducer.handleMemberSignup(1, "Summers, Buffy");
          Assert.assertEquals("key=1, value=SUMMERS, BUFFY\n", systemOutContent.toString());
    5. Implement the testHandleMemberSignup_error test:

      public void testHandleMemberSignup_error() {
          // Verify that the producer logs the error message to System.err if an error occurs when seding a record.
          // A text fixture called systemErrContent has already been set up in this class to capture System.err data.
          memberSignupsProducer.handleMemberSignup(1, "Summers, Buffy");
          mockProducer.errorNext(new RuntimeException("test error"));
          Assert.assertEquals("test error\n", systemErrContent.toString());
    6. Run your tests and make sure they pass:

      ./gradlew test

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