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.Â
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:Â
Python3
from locust import HttpUser, TaskSet, taskfrom locust import ResponseErrorimport jsonÂ
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class UserBehavior(TaskSet):Â
    def __init__(self, parent):        super(UserBehavior, self).__init__(parent)        self.token = "        "        self.headers = {}Â
    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()Â
    def login(self):        # admin login and retrieving it's access token        response = self.client.post( & quot                                    / login/"                                    ,                                    data={'username': 'admin',                                           'password': 'ZYT5nsg3565!'})Â
        return json.loads(response._content)['access']Â
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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: 
