Using Mocked Service Integrations - Amazon Step Functions
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Using Mocked Service Integrations

In Step Functions Local, you can test the execution paths of your state machines without actually calling integrated services by using mocked service integrations. To configure your state machines to use mocked service integrations, you create a mock configuration file. In this file, you define the desired output of your service integrations as mocked responses and the executions which use your mocked responses to simulate an execution path as test cases.

By providing the mock configuration file to Step Functions Local, you can test service integration calls by running state machines that use the mocked responses specified in the test cases instead of making actual service integration calls.

Note

If you don't specify mocked service integration responses in the mock configuration file, Step Functions Local will invoke the Amazon service integration using the endpoint you configured while setting up Step Functions Local. For information about configuring endpoints for Step Functions Local, see Setting Configuration Options for Step Functions Local.

Key concepts in this topic

This topic uses several concepts which are defined in the following list:

  • Mocked Service Integrations - Refers to Task states configured to use mocked responses instead of performing actual service calls.

  • Mocked Responses - Refers to mock data that Task states can be configured to use.

  • Test Cases - Refers to state machine executions configured to use mocked service integrations.

  • Mock Configuration File - Refers to mock configuration file that contains JSON, which defines mocked service integrations, mocked responses, and test cases.

Step 1: Specify Mocked Service Integrations in a Mock Configuration File

You can test Step Functions Amazon SDK and optimized service integrations using Step Functions Local. The following image shows the state machine defined in the State machine definition tab:


        Mocked service integration example.

To do this, you must create a mock configuration file containing sections as defined in Introducing structure of mock configuration.

  1. Create a file named MockConfigFile.json to configure tests with mocked service integrations.

    The following example shows a mock configuration file referencing a state machine with two defined states named LambdaState and SQSState.

    Mock configuration file example

    The following is an example of a mock configuration file which demonstrates how to mock responses from invoking a Lambda function and sending a message to Amazon SQS. In this example, the LambdaSQSIntegration state machine contains three test cases named HappyPath, RetryPath, and HybridPath which mock the Task states named LambdaState and SQSState. These states use the MockedLambdaSuccess, MockedSQSSuccess, and MockedLambdaRetry mocked service responses. These mocked service responses are defined in the MockedResponses section of the file.

    { "StateMachines":{ "LambdaSQSIntegration":{ "TestCases":{ "HappyPath":{ "LambdaState":"MockedLambdaSuccess", "SQSState":"MockedSQSSuccess" }, "RetryPath":{ "LambdaState":"MockedLambdaRetry", "SQSState":"MockedSQSSuccess" }, "HybridPath":{ "LambdaState":"MockedLambdaSuccess" } } } }, "MockedResponses":{ "MockedLambdaSuccess":{ "0":{ "Return":{ "StatusCode":200, "Payload":{ "StatusCode":200, "body":"Hello from Lambda!" } } } }, "LambdaMockedResourceNotReady":{ "0":{ "Throw":{ "Error":"Lambda.ResourceNotReadyException", "Cause":"Lambda resource is not ready." } } }, "MockedSQSSuccess":{ "0":{ "Return":{ "MD5OfMessageBody":"3bcb6e8e-7h85-4375-b0bc-1a59812c6e51", "MessageId":"3bcb6e8e-8b51-4375-b0bc-1a59812c6e51" } } }, "MockedLambdaRetry":{ "0":{ "Throw":{ "Error":"Lambda.ResourceNotReadyException", "Cause":"Lambda resource is not ready." } }, "1-2":{ "Throw":{ "Error":"Lambda.TimeoutException", "Cause":"Lambda timed out." } }, "3":{ "Return":{ "StatusCode":200, "Payload":{ "StatusCode":200, "body":"Hello from Lambda!" } } } } } }
    State machine definition

    The following is an example of a state machine definition called LambdaSQSIntegration, which defines two service integration task states named LambdaState and SQSState. LambdaState contains a retry policy based on States.ALL.

    { "Comment":"This state machine is called: LambdaSQSIntegration", "StartAt":"LambdaState", "States":{ "LambdaState":{ "Type":"Task", "Resource":"arn:aws:states:::lambda:invoke", "Parameters":{ "Payload.$":"$", "FunctionName":"HelloWorldFunction" }, "Retry":[ { "ErrorEquals":[ "States.ALL" ], "IntervalSeconds":2, "MaxAttempts":3, "BackoffRate":2 } ], "Next":"SQSState" }, "SQSState":{ "Type":"Task", "Resource":"arn:aws:states:::sqs:sendMessage", "Parameters":{ "QueueUrl":"https://sqs.us-east-1.amazonaws.com/123456789012/myQueue", "MessageBody.$":"$" }, "End": true } } }

    You can run the LambdaSQSIntegration state machine definition referenced in the mock configuration file using one of the following test cases:

    • HappyPath - This test mocks the output of LambdaState and SQSState using MockedLambdaSuccess and MockedSQSSuccess respectively.

      • The LambdaState will return the following value:

        "0":{ "Return":{ "StatusCode":200, "Payload":{ "StatusCode":200, "body":"Hello from Lambda!" } } }
      • The SQSState will return the following value:

        "0":{ "Return":{ "MD5OfMessageBody":"3bcb6e8e-7h85-4375-b0bc-1a59812c6e51", "MessageId":"3bcb6e8e-8b51-4375-b0bc-1a59812c6e51" } }
    • RetryPath - This test mocks the output of LambdaState and SQSState using MockedLambdaRetry and MockedSQSSuccess respectively. In addition, LambdaState is configured to perform four retry attempts. The mocked responses for these attempts are defined and indexed in the MockedLambdaRetry state.

      • The initial attempt ends with a task failure containing a cause and error message as shown in the following example:

        "0":{ "Throw": { "Error": "Lambda.ResourceNotReadyException", "Cause": "Lambda resource is not ready." } }
      • The first and second retry attempts end with a task failure containing a cause and error message as shown in the following example:

        "1-2":{ "Throw": { "Error": "Lambda.TimeoutException", "Cause": "Lambda timed out." } }
      • The third retry attempt ends with a task success containing state result from Payload section in the mocked Lambda response.

        "3":{ "Return": { "StatusCode": 200, "Payload": { "StatusCode": 200, "body": "Hello from Lambda!" } } }
        Note
        • For states with a retry policy, Step Functions Local will exhaust the retry attempts set in the policy until it receives a success response. This means that you must denote mocks for retries with consecutive attempt numbers and should cover all the retry attempts before returning a success response.

        • If you do not specify a mocked response for a specific retry attempt, for example, retry "3", the state machine execution will fail.

    • HybridPath - This test mocks the output of LambdaState. After LambdaState runs successfully and receives mocked data as a response, SQSState performs an actual service call to the resource specified in production.

    For information about how to start test executions with mocked service integrations, see Step 3: Run Mocked Service Integration Tests.

  2. Make sure that the mocked responses' structure conforms to the structure of actual service responses you receive when you make integrated service calls. For information about the structural requirements for mocked responses, see Configuring mocked service integrations.

    In the previous example mock configuration file, the mocked responses defined in MockedLambdaSuccess and MockedLambdaRetry conform to the structure of actual responses that are returned from calling HelloFromLambda.

    Important

    Amazon service responses can vary in structure between different services. Step Functions Local doesn't validate if mocked response structures conform to actual service response structures. You must ensure that your mocked responses conform to actual responses before testing. To review the structure of service responses, you can either perform the actual service calls using Step Functions or view the documentation for those services.

Step 2: Provide the Mock Configuration File to Step Functions Local

You can provide the mock configuration file to Step Functions Local in one of the following ways:

Docker
Note

If you're using the Docker version of Step Functions Local, you can provide the mock configuration file using an environment variable only. In addition, you must mount the mock configuration file onto the Step Functions Local container at the initial server boot-up.

Mount the mock configuration file onto any directory within the Step Functions Local container. Then, set an environment variable named SFN_MOCK_CONFIG that contains the path to the mock configuration file in the container. This method enables the mock configuration file to be named anything as long as the environment variable contains the file path and name.

The following command shows the format to start the Docker image.

docker run -p 8083:8083 --mount type=bind,readonly,source={absolute path to mock config file},destination=/home/StepFunctionsLocal/MockConfigFile.json -e SFN_MOCK_CONFIG="/home/StepFunctionsLocal/MockConfigFile.json" amazon/aws-stepfunctions-local

The following example uses the command to start the Docker image.

docker run -p 8083:8083 --mount type=bind,readonly,source=/Users/admin/Desktop/workplace/MockConfigFile.json,destination=/home/StepFunctionsLocal/MockConfigFile.json -e SFN_MOCK_CONFIG="/home/StepFunctionsLocal/MockConfigFile.json" amazon/aws-stepfunctions-local
JAR File

Use one of the following ways to provide the mock configuration file to Step Functions Local:

  • Place the mock configuration file in the same directory as Step FunctionsLocal.jar. When using this method, you must name the mock configuration file MockConfigFile.json.

  • In the session running Step Functions Local, set an environment variable named SFN_MOCK_CONFIG, to the full path of the mock configuration file. This method enables the mock configuration file to be named anything as long as the environment variable contains its file path and name. In the following example, the SFN_MOCK_CONFIG variable is set to point at a mock configuration file named EnvSpecifiedMockConfig.json, located in the /home/workspace directory.

    export SFN_MOCK_CONFIG="/home/workspace/EnvSpecifiedMockConfig.json"
Note
  • If you do not provide the environment variable SFN_MOCK_CONFIG to Step Functions Local, by default, it will attempt to read a mock configuration file named MockConfigFile.json in the directory from which you launched Step Functions Local.

  • If you place the mock configuration file in the same directory as Step FunctionsLocal.jar and set the environment variable SFN_MOCK_CONFIG, Step Functions Local will read the file specified by the environment variable.

Step 3: Run Mocked Service Integration Tests

After you create and provide a mock configuration file to Step Functions Local, run the state machine configured in the mock configuration file using mocked service integrations. Then check the execution results using an API action.

  1. Create a state machine based on the previously mentioned definition in the mock configuration file.

    aws stepfunctions create-state-machine \ --endpoint http://localhost:8083 \ --definition "{\"Comment\":\"Thisstatemachineiscalled:LambdaSQSIntegration\",\"StartAt\":\"LambdaState\",\"States\":{\"LambdaState\":{\"Type\":\"Task\",\"Resource\":\"arn:aws:states:::lambda:invoke\",\"Parameters\":{\"Payload.$\":\"$\",\"FunctionName\":\"arn:aws:lambda:us-east-1:123456789012:function:HelloWorldFunction\"},\"Retry\":[{\"ErrorEquals\":[\"States.ALL\"],\"IntervalSeconds\":2,\"MaxAttempts\":3,\"BackoffRate\":2}],\"Next\":\"SQSState\"},\"SQSState\":{\"Type\":\"Task\",\"Resource\":\"arn:aws:states:::sqs:sendMessage\",\"Parameters\":{\"QueueUrl\":\"https://sqs.us-east-1.amazonaws.com/123456789012/myQueue\",\"MessageBody.$\":\"$\"},\"End\":true}}}" \ --name "LambdaSQSIntegration" --role-arn "arn:aws:iam::123456789012:role/service-role/LambdaSQSIntegration"
  2. Run the state machine using mocked service integrations.

    To use the mock configuration file, make a StartExecution API call on a state machine configured in the mock configuration file. To do this, append the suffix, #test_name, to the state machine ARN used by StartExecution. test_name is a test case, which is configured for the state machine in the same mock configuration file.

    The following command is an example that uses the LambdaSQSIntegration state machine and mock configuration. In this example, the LambdaSQSIntegration state machine is executed using the HappyPath test defined in Step 1: Specify Mocked Service Integrations in a Mock Configuration File. The HappyPath test contains the configuration for the execution to handle mock service integration calls that LambdaState and SQSState states make using the MockedLambdaSuccess and MockedSQSSuccess mocked service responses.

    aws stepfunctions start-execution \ --endpoint http://localhost:8083 \ --name executionWithHappyPathMockedServices \ --state-machine arn:aws:states:us-east-1:123456789012:stateMachine:LambdaSQSIntegration#HappyPath
  3. View the state machine execution response.

    The response to calling StartExecution using a mocked service integration test is same as the response to calling StartExecution normally, which returns the execution ARN and start date.

    The following is an example response to calling StartExecution using the mocked service integration test:

    { "startDate":"2022-01-28T15:03:16.981000-05:00", "executionArn":"arn:aws:states:us-east-1:123456789012:execution:LambdaSQSIntegration:executionWithHappyPathMockedServices" }
  4. Check the execution's results by making a ListExecutions, DescribeExecution, or GetExecutionHistory API call.

    aws stepfunctions get-execution-history \ --endpoint http://localhost:8083 \ --execution-arn arn:aws:states:us-east-1:123456789012:execution:LambdaSQSIntegration:executionWithHappyPathMockedServices

    The following example demonstrates parts of a response to calling GetExecutionHistory using the execution ARN from the example response shown in step 2. In this example, the output of LambdaState and SQSState is the mock data defined in MockedLambdaSuccess and MockedSQSSuccess in the mock configuration file. In addition, the mocked data is used the same way that data returned by performing actual service integration calls would be used. Also, in this example, the output from LambdaState is passed onto SQSState as input.

    { "events": [ ... { "timestamp": "2021-12-02T19:39:48.988000+00:00", "type": "TaskStateEntered", "id": 2, "previousEventId": 0, "stateEnteredEventDetails": { "name": "LambdaState", "input": "{}", "inputDetails": { "truncated": false } } }, ... { "timestamp": "2021-11-25T23:39:10.587000+00:00", "type": "LambdaFunctionSucceeded", "id": 5, "previousEventId": 4, "lambdaFunctionSucceededEventDetails": { "output": "{\"statusCode\":200,\"body\":\"\\\"Hello from Lambda!\\\"\"}", "outputDetails": { "truncated": false } } }, ... "timestamp": "2021-12-02T19:39:49.464000+00:00", "type": "TaskStateEntered", "id": 7, "previousEventId": 6, "stateEnteredEventDetails": { "name": "SQSState", "input": "{\"statusCode\":200,\"body\":\"\\\"Hello from Lambda!\\\"\"}", "inputDetails": { "truncated": false } } }, ... { "timestamp": "2021-11-25T23:39:10.652000+00:00", "type": "TaskSucceeded", "id": 10, "previousEventId": 9, "taskSucceededEventDetails": { "resourceType": "sqs", "resource": "sendMessage", "output": "{\"MD5OfMessageBody\":\"3bcb6e8e-7h85-4375-b0bc-1a59812c6e51\",\"MessageId\":\"3bcb6e8e-8b51-4375-b0bc-1a59812c6e51\"}", "outputDetails": { "truncated": false } } }, ... ] }