Bots simulate participants playing your app. They click through each page, fill out forms, and make sure that everything works properly.
This feature is designed for lazy people who would prefer for oTree to automatically test their apps for them. And oTree Studio can even design your bot code for you, so the whole process (writing and running bots) involves barely any effort.
- Add bots to your app (see instructions below)
- In your session config, set
- Run your server and create a session. The pages will auto-play with browser bots, once the start links are opened.
- If using Heroku, make sure the second dyno is enabled.
In oTree Studio, go to the “Tests” section of your app.
Click the button to auto-write bots code.
If you want to refine the code that was generated
(such as adding
read the below sections.
If you are using a text editor, go to
You should make one
yield per page submission. For example:
yield pages.Start yield pages.Survey, dict(name="Bob", age=20)
Here, we first submit the
Start page, which does not contain a form.
The following page has 2 form fields, so we submit a dict.
The test system will raise an error if the bot submits invalid input for a page, or if it submits pages in the wrong order.
if statements to play any player or round number. For example:
if self.round_number == 1: yield pages.Introduction if self.player.id_in_group == 1: yield pages.Offer, dict(offer=30) else: yield pages.Accept, dict(offer_accepted=True)
if statements can depend on
Ignore wait pages when writing bots.
Your bot code should just play 1 round at a time.
oTree will automatically execute it
expect() function was introduced in September 2019.
Previously we recommended using
assert statements, which are still OK
expect() can report errors more clearly.
You can use
expect statements to ensure that your code is working as you expect.
from otree.api import expect expect(self.player.num_apples, 100) yield pages.Eat, dict(apples_eaten=1) expect(self.player.num_apples, 99) yield pages.SomeOtherPage
self.player.num_apples is not 99, then you will be alerted with an error.
You can also use expect with 3 arguments, like
expect(self.player.budget, '<', 100).
This will verify that
self.player.budget is less than 100.
You can use the following operators:
Testing form validation¶
If you use form validation,
you should test that your app is correctly rejecting invalid input from the user,
For example, let’s say you have this page:
class MyPage(Page): form_model = 'player' form_fields = ['int1', 'int2'] @staticmethod def error_message(player, values): if values["int1"] + values["int2"] != 100: return 'The numbers must add up to 100'
Here is how to test that it is working properly:
from otree.api import SubmissionMustFail yield SubmissionMustFail(pages.MyPage, dict(int1=99, int2=0)) yield pages.MyPage, dict(int1=99, int2=1)
The bot will submit
MyPage twice. If the first submission succeeds,
an error will be raised, because it is not supposed to succeed.
Checking the HTML¶
self.html contains the HTML of the page you are about to submit.
You can use this together with
from otree.api import expect if self.player.id_in_group == 1: expect(self.player.is_winner, True) print(self.html) expect('you won the game', 'in', self.html) else: expect(self.player.is_winner, False) expect('you did not win', 'in', self.html) yield pages.Results # etc...
self.html is updated with the next page’s HTML, after every
Linebreaks and extra spaces are ignored.
Automatic HTML checks¶
An error will be raised if the bot is trying to submit form fields that are not actually found in the page’s HTML, or if the page’s HTML is missing a submit button.
In these cases, you should disable the HTML check by using
check_html=False. For example, change this:
yield pages.MyPage, dict(foo=99)
from otree.api import Submission yield Submission(pages.MyPage, dict(foo=99), check_html=False)
(If you used
the two code samples would be equivalent.)
Simulate a page timeout¶
You can use
from otree.api import Submission yield Submission(pages.MyPage, dict(foo=99), timeout_happened=True)