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 websites and checking the 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.
Specialty of locust:
- Test scenarios can be written in Python
- Distributed and scalable
- Web-based UI
- Any system can be tested using this tool
Installation: 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 HttpUser, 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)}
self.login()
def login(self):
# admin login and retrieving it's access token
response = self.client.post( & quot
/ login/"
,
data={'username': 'admin',
'password': 'ZYT5nsg3565!'})
return json.loads(response._content)['access']
class WebsiteUser(HttpUser):
# 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 locustfile.py, and open the terminal in the directory of the above created file. Then write the following command in the terminal.
locust
Note: By default locust searches for locustfile.py. After the successful execution of the above command, you should open a browser and hit http://127.0.0.1:8089 The Locust UI will appear like below: 
