Using Locust to Run Tests in Power Platform

This document determines the approach for writing automated tests for Power Platform, Power Automate and Dataverse.

Challenges

Testing Power Apps and Power Automate flows can be as simple as running the test from the User Interface (UI). But for a more robust test, when there are different parts of the application running in different services there is a need to add some tooling that is able to handle that.

Overcoming the challenges

The tool used in this case was Locust. Because it would allow different tests to run with few changes to the tests cases created to test a part of the application.

Considering there is an entry point ready to receive REST calls that will trigger the Power Automate flows it is possible to insert data into Dataverse and confirm the data is there.

It is also possible to make changes to Dataverse that would trigger Power Automate flows to update data in a data set (Azure Tables, Database, Files) outside Dataverse.

Tests in Power Platform and Dataverse

The diagram below demonstrates in high level how tests can be executed for Power Platform and Dataverse:

In the next sections it will be described the overall process as shown in the diagram:

• Message to Open
• Message to Close

A more detailed guide is available as a recipe, where a sample source code is published.

Message to Open

Locust starts the process by sending a request to Service Bus (in this case Service Bus was available in the solution, but any other tool to call the API can be used, even a REST call to the API directly).

This message is routed to the Connector API developed in Power Platform. This connector will traffic the message between the customer tenant and the Microsoft Platform. So it will call the Power Automate flow, that has the logic to send the message to be stored in Dataverse.

Notice that neither the connector API nor the flows are highlighted. This means that these services do not provide messages to the testing tool. The flow is an asynchronous and the HTTP reply will be, for example, 202 meaning it was accepted for processing.

Locust will then look for the message in Dataverse. If the message arrive there it is assumed that the process was successful.

Message to Close

In the current scenario, changing the status in Dataverse to closed using the Dataverse API will trigger a flow that will send this message back to the customer tenant.

As this is an update operation in Dataverse, a PATCH request is sent to the API to change the value in there. This change will trigger the Power Automate flow that will process the message, doing any transformation needed, to the Connector API.

The connector API will send this message to the Service Bus, that will route it to a Database or other data storage the customer considers in the solution.

The case could potentially be checked in the Service Bus, but its architecture does not allow the test service to retrieve a specific message so three scenarios could happen if the test is done like this:

1. The test service would retrieve the message in the first call and the case could be considered successful;
2. The test service would retrieve several messages before finding the message for for the registry closed in Dataverse. In this case the test will also be considered successful;
3. The test service would retrieve several messages and the close registry could not be found because the Service Bus already processed the message and sent it to the database. In this case it would be a false-negative test, as the message was successfully processed.

So the test will not check the Service Bus for the message and will go checking the database directly if the registry was updated there.

Prerequisites

• Docker
• Locust

Using Locust

Locust in Docker

In this case, Docker needs to be installed. In this document a docker-compose version of this solution will be presented.

Configuring Docker and docker-compose

Locust is well documented regarding the installation and usage with Docker, so that part will not be covered in this document.

Alternative: run Locust locally

Locust is written in Python, so if one prefers to run it locally, without Docker, a call in the command line would work:

locust -f locustfile.py --host http://127.0.0.1:8089 --headless -u 10 -t 120s Test

This will run Test for 120 seconds, using 10 users, without an User Interface. When the time is up, the process will kill itself and returns to the command prompt.

Be aware that this process will not generate a report other the what is displayed in the screen.

Other options can be found in the Locust documentation

Writing the locust test file for reuse

Considering that multiple tests are run in a project, it is smart to have as many tests as possible. At the same time, it is also smart to have as few places to update the tests as possible.

Therefore, Locust is a tool to write not only Load Tests, but also other types of tests, like End-to-End and Integration tests.

Here is an example:

def function1(self):
    // do something

def function2(self):
    // do something

def function3(self):
    // do something

class e2e_test(SequentialTaskSet):
    @task
    function1()
    function2()
    function3()

class integration_test1(SequentialTaskSet):
    @task
    function1()
    function2()

class integration_test2(SequentialTaskSet):
    @task
    function2()
    function3()

class load_test(SequentialTaskSet):
    @task
    function1()
    function3()

class ExecuteE2ETest(HttpUser):
    """Start test of the classes."""
    tasks = [e2e_test]
    wait_time = constant(30.0)

class ExecuteIntegrationTest1(HttpUser):
    """Start test of the classes."""
    tasks = [integration_test1]
    wait_time = constant(30.0)

class ExecuteIntegrationTest2(HttpUser):
    """Start test of the classes."""
    tasks = [integration_test2]
    wait_time = constant(30.0)

class ExecuteLoadTest(HttpUser):
    """Start test of the classes."""
    tasks = [load_test]
    wait_time = between(3.0, 9.0)

Then the tests can be called as ExecuteE2ETest, ExecuteIntegrationTest, or ExecuteLoadTest, depending on what test is supposed to run.

The following will work for end-to-end tests in docker-compose:

version: '3'

services:
  master:
    image: locustio/locust
    ports:
     - "8089:8089"
    volumes:
      - ./:/mnt/locust
    environment:
        LOCUST_USERS: 1
        LOCUST_EXPECT_WORKERS: 1
        LOCUST_SPAWN_RATE: 1
        LOCUST_RUN_TIME: 120s
    command: -f /mnt/locust/locustfile.py --master -H http://master:8089 ExecuteE2ETest

  worker:
    image: locustio/locust
    volumes:
      - ./:/mnt/locust
    command: -f /mnt/locust/locustfile.py --worker --master-host master ExecuteE2ETest

This will run the integration test:

version: '3'

services:
  master:
    image: locustio/locust
    ports:
     - "8089:8089"
    volumes:
      - ./:/mnt/locust
    environment:
        LOCUST_USERS: 1
        LOCUST_EXPECT_WORKERS: 1
        LOCUST_SPAWN_RATE: 1
        LOCUST_RUN_TIME: 20s
    command: -f /mnt/locust/locustfile.py --master -H http://master:8089 ExecuteIntegrationTest1

  worker:
    image: locustio/locust
    volumes:
      - ./:/mnt/locust
    command: -f /mnt/locust/locustfile.py --worker --master-host master ExecuteIntegrationTest1

And the below will execute the load test:

version: '3'

services:
  master:
    image: locustio/locust
    ports:
     - "8089:8089"
    volumes:
      - ./:/mnt/locust
    environment:
        LOCUST_USERS: 10
        LOCUST_EXPECT_WORKERS: 1
        LOCUST_SPAWN_RATE: 10
        LOCUST_RUN_TIME: 300s
    command: -f /mnt/locust/locustfile.py --master -H http://master:8089 ExecuteLoadTest

  worker:
    image: locustio/locust
    volumes:
      - ./:/mnt/locust
    command: -f /mnt/locust/locustfile.py --worker --master-host master ExecuteLoadTest

All the 3 scripts are practically doing the same thing. There are two places to be updated:

1. The environment section handles the load of the test: - How many users and workers should be used? - What is the spawn rate? Should the test run will many users at the same time? - For how long should the test run?
2. The command line handles the command to run locust and which test should it run. If command is specified, only one test will be executed, not the whole script.

By changing this values alone it is possible to reuse the test cases to cover different test strategies.

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Last update: January 31, 2022