Add "testdata from csv" example.

examples/testdata_from_csv.csv

@@ -0,0 +1,2 @@
+myuser1@example.com,password1
+myuser2@example.com,password2

examples/testdata_from_csv.py

@@ -0,0 +1,55 @@
+"""
+This shows an easy way to get testdata from a csv file into locust and use it for requests
+"""
+
+from locust import FastHttpUser, events, run_single_user, task
+
+import csv
+import os
+
+csvfile = open(os.path.join(os.path.dirname(__file__), "testdata_from_csv.csv"))
+iter = csv.reader(csvfile)
+
+
+class DemoUser(FastHttpUser):
+    @task
+    def t(self):
+        try:
+            username, password = next(iter)
+        except StopIteration:
+            # go back to start of the file once its been exhausted
+            csvfile.seek(0, 0)
+            username, password = next(iter)
+        with self.rest("POST", "/authenticate", json={"username": username, "password": password}) as resp:
+            if message := resp.js and resp.js.get("message"):
+                if not "Welcome" in message:
+                    resp.failure(f"bad response: {message}")
+
+
+# We'll now add endpoints to Locust's own WebUI to use as a target for the test.
+# This means so you can't use headless or run_single_user, unless you also start a "headful" Locust instance.
+#
+# It is not very relevant to what this example is explaining, so feel free to ignore it.
+
+FastHttpUser.host = "http://127.0.0.1:8089"
+
+from flask import request
+
+
+@events.init.add_listener
+def locust_init(environment, **kwargs):
+    if environment.web_ui:
+
+        @environment.web_ui.app.route("/authenticate", methods=["POST"])
+        def authenticate():
+            username = request.get_json()["username"]
+            return {"message": f"Welcome {username}!"}
+
+        @environment.web_ui.app.route("/checkout/confirm", methods=["POST"])
+        def checkout_confirm():
+            foo = request.get_json()["foo"]
+            return {"orderId": 42}
+
+
+if __name__ == "__main__":
+    run_single_user(DemoUser)