Log in to Drupal 8 with locust.io

locustfile.py

from locust import HttpLocust, TaskSet, task
from bs4 import BeautifulSoup

class WebsiteTasks(TaskSet):
    def on_start(self):
        """
        on_start is called when a Locust start before,
        any task is scheduled
        """
        self.login()

    def login(self):
        # Get form build ID to pass back to Drupal on login.
        resp = self.client.get("/user")
        parsed_html = BeautifulSoup(resp.content)
        form_build_id = parsed_html.body.find('input', {'name': 'form_build_id'})['value']

        self.client.post("/user/login", {
            "name": "LoadTester",
            "pass": "test",
            "form_id": "user_login_form",
            "form_build_id": form_build_id,
            "op": "Log in"
        })


    # Add some pages to load.
    @task
    def index(self):
        self.client.get("/")

    @task
    def search(self):
        self.client.get("/another/page")

I needed to add this at the bottom for it to work

class WebsiteUser(HttpUser):
    tasks = [WebsiteTasks]
    wait_time = between(5, 10)