Locust: Users, Tasks & wait_time

Locust is an open-source load-testing tool where test scenarios are written as plain Python code -- not a proprietary DSL or record-and-replay script -- letting developers use familiar language constructs and existing libraries directly in their test logic.

Defining a User

from locust import HttpUser, task, between

class WebsiteUser(HttpUser):
    wait_time = between(1, 5)  # think time between tasks

    @task(3)
    def browse_home(self):
        self.client.get("/")

    @task(1)
    def checkout(self):
        self.client.post("/checkout", json={"item": "widget"})

Task Weights

@task(3) is chosen 3x as often as a default-weight task -- letting a scenario model realistic action frequency, like browsing happening far more often than checking out.

wait_time: Realistic Think Time

wait_time simulates the pause a real user takes between actions -- producing more realistic load patterns than tasks executing back-to-back with zero delay.

Handling Authentication

class AuthenticatedUser(HttpUser):
    def on_start(self):
        # runs once per simulated user before its tasks begin
        response = self.client.post("/login", json={"user": "test"})
        self.token = response.json()["token"]

    @task
    def view_dashboard(self):
        self.client.get("/dashboard", headers={"Authorization": self.token})