Scenarios

In Cicada, tests are organized into Scenarios to describe how they are run. A scenario's Load Model is responsible for managing Users and administering work to users if necessary. Effectively, a single test is a Scenario with one or more Users

Load Model

Let's take a look at the example test:

@scenario(engine)
def my_first_test(context):
    assert 2 + 2 == 4

    return "Passed!"

By default the scenario when run will start 1 user and have it run 1 time. Here is the pseudocode for how that basic load model would work:

def run_once(scenario_commands: ScenarioCommands, context: dict):
    scenario_commands.scale_users(1)
    scenario_commands.add_work(1)

    latest_results = []

    while latest_results == []:
        latest_results = scenario_commands.get_latest_results()

        time.sleep(1)

    scenario_commands.aggregate_results(latest_results)
    scenario_commands.verify_results(latest_results)

    scenario_commands.scale_users(0)

We can override that by specifying a different load model:

from cicadad.core.decorators import load_model
...

def n_iterations(iterations: int, users: int):
    def closure(scenario_commands: ScenarioCommands, context: dict):
        scenario_commands.scale_users(users)
        scenario_commands.add_work(iterations)

        results = []

        while len(results) < iterations:
            latest_results = scenario_commands.get_latest_results()

            scenario_commands.aggregate_results(latest_results)
            scenario_commands.verify_results(latest_results)

            results.extend(latest_results)
            time.sleep(1)

        scenario_commands.scale_users(0)

    return closure

@scenario(engine)
@load_model(n_iterations(100, 10))
def my_first_test(context):
    assert 2 + 2 == 4

    return "Passed!"

This creates a load model to run 10 users a shared total of 100 times until completion.

tip

This type of load model is built-in at cicadad.core.scenario.n_iterations. Don't write your own version of this!

Scenario Commands

You may have noticed the argument for ScenarioCommands passed to the load model. This class is used to provide an interface for managing users during a scenario. It has the following features:

• Scale Users - Change the number of running users.
• Start Users - Increase the number of running users.
• Stop Users - Decrease the number of running users.
• Add Work - Increase the number of iterations for the user pool to run.
• Get Latest Results - Retrieve the latest results posted by the user pool.
• Aggregate Results - Save an aggregated result based on the current aggregate and latest results to the scenario.
• Verify Results - Check the latest results and return error strings if errors among them are found.