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Load testing using LOCUST

  • Difficulty Level : Easy
  • Last Updated : 19 Feb, 2020

Locust is an open source load testing tool. Load testing is a type of software testing that is conducted to check the tolerance/behavior of the system under a specific expected load. The target of locust is load-testing web sites and checking number of concurrent users a system can handle.
During a locust test, a swarm of locusts will attack the target i.e website. The behavior of each locust is configurable and the swarming process is monitored from a web UI in real-time.

Speciality of locust:

  • Test scenarios can be written in Python
  • Distributed and scalable
  • Web-based UI
  • Any system can be tested using this tool


Locust can be installed with pip.

pip install locust

Once the locust is successfully installed, a locust command should be available in your shell.
To see more available options:

locust --help

Getting started:

from locust import HttpLocust, TaskSet, task
from locust import ResponseError
import json
class UserBehavior(TaskSet):
    def __init__(self, parent):
        super(UserBehavior, self).__init__(parent)
        self.token = ""
        self.headers = {}
    def on_start(self):
        # The on_start method is called 
        # when a simulated user starts 
        # executing that TaskSet class
        self.token = self.login()
        self.headers = {'Authorization': 'Bearer {}'.format(self.token)}
    def login(self):
        # admin login  and retrieving it's access token
        response ="/login/",
                                    data = {'username': 'admin',
                                          'password': 'ZYT5nsg3565!'})
        return json.loads(response._content)['access']
class WebsiteUser(HttpLocust):
    # The task_set attribute should point
    # to a TaskSet class which defines 
    # the behaviour of the user
    task_set = UserBehavior
    min_wait = 5000
    max_wait = 9000

Start locust:
To run the above code, create a Python file named, and open the terminal in the directory of the above created file. Then write the following command in the terminal.


Note: By default locust searches for

After the successful execution of the above command, you should open a browser and hit

The Locust UI will appear like below:

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