Simulating Consumers

Applies to ReadyAPI 3.9, last modified on July 29, 2021

Consuming events is one part of message exchange in Kafka, the other being producing events. You can use ReadyAPI to simulate an event consumer and read events from topics on your Kafka broker.

Use case

Let's consider an example where you want to check that your payment system works correctly. The system reads events from the payments topic and, if the payment is successful, publishes events to the payment-confirmation topic.

So, to make sure the system works, you can use ReadyAPI to simulate a consumer. You can subscribe to the payment-confirmation topic and assert that events are published to it.

Tip: If you want to simulate a complex scenario, you can also use ReadyAPI to simulate an event producer and publish payment events to the system.

Consume events

1. Add a Kafka API to the project

To start testing Kafka APIs, you should first add one to the project. To learn how to do it, see Adding a Kafka API to the Project.

2. Create a test step

To produce a Kafka event in ReadyAPI, you use the API Connection test step based on a Subscribe operation:

  1. Open a test case and add API Connection Test Step.

  2. In the dialog that appears, select a Subscribe operation and click Add Test Step:


– or –

  1. Right-click a Subscribe operation in the APIs node in the Navigator and select Add to Test Case.

  2. In the dialog that appears, select a test case and click Add Test Step:


3. Subscribe to the topic

To consume events from the topic, select Connect. ReadyAPI will connect to the topic and consume events that come to the topic. The test step will stay connected to the topic until its disconnect criteria are met.

Simulating Kafka consumer: Subscribe to the topic

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In the sections below, you can read more about connection settings and the message editor. Kafka authentication settings are covered here: Authentication in Kafka.

4. Add assertions

To validate messages in the topic, add assertions to the test step. Assertions will be applied to every message that the Subscribe test step consumes from the topic.

Simulating Kafka consumer: Add an assertion

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Tip: Assertion groups are particularly useful for the API Connection test step because one test step receives multiple messages. For example, you can add two JSONPath Match assertions to an assertion group and configure it so that the test step passes if either of those assertions passes.

To learn more about the Assertions panel and assertions available in the API Connection test step, see API Connection Test Step.

Test step settings

Test step toolbar

The test step toolbar contains settings that allow you to modify the connection and authorization settings for the test step:

API Connection test step: Subscribe toolbar

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Connection settings

To open the connection settings, select Connection Settings in the test step toolbar.

Option Description
Confluent Settings

Used to connect to the Confluent schema registry. Only available when the JSON via Avro message format is selected.

  • Schema Registry URL – The URL of the schema registry.
  • Registry Authorization – The authorization profile that will be used to authenticate to the schema registry. To learn more about registry schema authentication, see Authentication in Kafka.
Subscribe Settings

Other parameters that your Kafka provider might require.

Close Subscription When

Settings that dictate when the subscription to the topic will be closed. Based on the mode chosen, the connection will close when either one of these conditions is met or when all of them are.

  • Idle Time – The time during which no new events are published to the topic.
  • Messages Received – The number of messages that the test step will receive before closing the connection. (Maximum: 500)
  • Run Time – The time elapsed after connecting to the topic.
Reset to Default

Resets connection settings to default. Default settings depend on the environment selected:

  • If no environment is selected, default settings are Idle Time = 60, Messages Received = 50, and Run Time = 60. Confluent Settings and Subscribe Settings are cleared.

  • If an environment is selected, default settings will be taken from the environment settings.

Property list

You can also change the test step behavior by using the step properties on the API Connection Test Step Properties panel in the Navigator.

Property Description

The test step’s name.


Text that describes the test step.

Idle Time

Duplicates the Idle Time setting in the Connection Settings.

Messages Received

Duplicates the Messages Received setting in the Connection Settings.

Run Time

Duplicates the Run Time setting in the Connection Settings.

Received data

The Received Data window is where you will see the messages that the test step consumes from the topic.

API Connection test step: Received Data window

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  • Message format – The format of messages in the topic. Currently, two formats are supported:

    • JSON – Messages in the topic are regular JSONs. In this case, ReadyAPI will simply retrieve the messages without processing them.

    • JSON via Avro (Confluent) – Messages in the topic have been serialized using a Confluent schema registry. In this case, ReadyAPI will deserialize them using the schema registry. To set up a connection to the schema registry, go to Connection Settings.

  • Metadata – Parameters that were passed with the message.

    There are two types of parameters:

    • Header – Kafka headers that will be sent with the message.

    • Kafka – Two parameters, Key and Partition, that each Kafka message has.

  • Data – The message itself.

Next Steps

See Also

Kafka Testing
API Connection Test Step

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