Unittesting for Kivy framework

unittest, testing, debug, kivy, python, tutorial, unit-testing
pip install kivyunittest==0.1.8



Test more, cry less!

This script is meant to launch a folder of your tests which will behave as one big test suite. It's done this way because of necessity having a fresh python interpreter for each Kivy application test to run without mistakes (otherwise mess from previous App().run() interferes).

Each unittest file in a folder consisting of tests must start with test_ prefix and end with .py

Run from console:

python -m kivyunittest --folder "FOLDER" --pythonpath "FOLDER"

Without --folder flag the file assumes it's placed into a folder full of tests presumably as __init__.py. It makes a list of files, filters everything not starting with test_ and ending with .py and runs each test.

Flag --pythonpath appends a folder to the sys.path automatically, therefore it's not necessary to include it in each test manually.


If there is an error of whatever kind that unittest recognizes as failure, KivyUnitTest will save the name of the test and its log. When the testing ends all error logs are put together into console divided by pretty headers with test's name.

Writing Unit Test for Kivy application

Basic tests

When the Kivy application starts, it creates a loop and until the loop is there, nothing will execute after App().run() line. That's why we need to probe the loop.

This can be achieved by a simple time.sleep() as you've surely noticed sooner when trying to pause the app for a while. That's exactly what a custom unittest for Kivy does - pauses the main loop as much as possible as a scheduled interval and executes the testing run_test function.


import unittest

import os
import sys
import time
import os.path as op
from functools import partial
from kivy.clock import Clock

First we need to set up importing of the application set main_path to be the folder of main.py e.g. when you have tests in <app dir>/tests/test_example.py. Or choose the folder with the --pythonpath flag.

main_path = op.dirname(op.dirname(op.abspath(__file__)))

Import your main class that inherits from App (class My(App):) or even additional stuff that's not connected with App class or its children.

from main import My

class Test(unittest.TestCase):
    # sleep function that catches ``dt`` from Clock
    def pause(*args):

    # main test function
    def run_test(self, app, *args):
        Clock.schedule_interval(self.pause, 0.000001)

        # Do something

        # Comment out if you are editing the test, it'll leave the
        # Window opened.

Create an instance of your application, put it as a parameter into partial (so that you could access it later), schedule main function with Clock and launch the application (working Window will appear).

    # same named function as the filename(!)
    def test_example(self):
        app = My()
        p = partial(self.run_test, app)
        Clock.schedule_once(p, 0.000001)

if __name__ == '__main__':

Intermediate tests

This kind of tests is used directly for testing in the Kivy core and might not be easy and/or suitable enough for your needs, however it brings a way extended control over the testing environment. In this test you can render each frame manually, move Clock each tick on your own and dispatch raw input from (mocked) providers through MotionEvent.

There is a class with all necessary stuff prepared in the background, so that it launches a Kivy window, but waits for you to move it further e.g. if you decide to render() a widget.

from kivy.tests.common import GraphicUnitTest

from kivy.input.motionevent import MotionEvent
from kivy.graphics import Color, Point
from kivy.uix.widget import Widget
from kivy.base import EventLoop
from math import sqrt

After you import MotionEvent, you can create own class that inherits from it and use it later as a mocked input. We will use sx and sy which are just positions on X and Y axis in 0 - 1 range (percents, if you will). This class will dispatch a touch.

class UTMotionEvent(MotionEvent):
    def depack(self, args):
        self.is_touch = True
        self.sx = args['sx']
        self.sy = args['sy']
        self.profile = ['pos']
        super(UTMotionEvent, self).depack(args)

If we know how to assemble a class to create a touch input, we might draw something with it as well. Kivy includes a nice demo, Touchtracer, for showcasing multitouch. We fetch calculate_points from that example. It basically returns a new set of points we'll input to a drawing function.

# taken from Kivy's Touchtracer
def calculate_points(x1, y1, x2, y2):
    dx = x2 - x1
    dy = y2 - y1
    dist = sqrt(dx * dx + dy * dy)
    o = []
    m = dist
    for i in range(1, int(m)):
        mi = i / m
            x1 + dx * mi,
            y1 + dy * mi
    return o

For drawing we'll use a very similar thing to the one used in the Touchtracer. Let's draw a Point on on_touch_down event. Then, if we move the touch append new points along the line between an old and a new point and draw them.

# core taken from Kivy's Touchtracer
class WidgetCanvasDraw(Widget):
    def on_touch_down(self, touch):
        win = self.get_parent_window()
        ud = touch.ud

        with self.canvas:
            Color(1, 0, 0, 1)
            ud['lines'] = Point(points=(
                touch.x, touch.y

        return True

    def on_touch_move(self, touch):
        if touch.grab_current is not self:
        ud = touch.ud

        points = ud['lines'].points
        oldx, oldy = points[-2], points[-1]

        points = calculate_points(oldx, oldy, touch.x, touch.y)

        if not points:

        add_point = ud['lines'].add_point
        for idx in range(0, len(points), 2):
                points[idx + 1]

    def on_touch_up(self, touch):
        if touch.grab_current is not self:

We have input, drawing behavior, let's set up a test. You might want to get used to this "template" if you intend to use the GraphicsUnitTest class. It's not that scary though. Set a class attribute framecount to zero, prepare some debugging behavior (setUp prepares a new Window, tearDown purges it). After overriding them with empty functions, such actions won't happen.

class WidgetDrawTestCase(GraphicUnitTest):
    framecount = 0

    # debug test with / stop destroying window
    # def tearDown(self, *_): pass
    # def setUp(self, *_): pass

We make sure the Window is available to us with EventLoop, prepare all out widgets and then call EventLoop.idle() which makes a lot of internals ready for an application to show like you are used to it. More or less.

def test_touch_draw(self):
    # get Window instance for creating visible
    # widget tree and for calculating coordinates
    win = EventLoop.window

    # add widget for testing
    child = WidgetCanvasDraw()

    # get widgets ready

You can happily start testing now.

The little bit problematic part comes now, because you have to be sure where you want your touch to go and do it in 0 - 1 range, so that the test works even after Window resizing. Absolute values are not the way you want to go. Always try to generalise the movement and find a way how to simplify them into a small list.

# default "cursor" position in the middle
pos = [win.width / 2.0, win.height / 2.0]

# default pos, new pos
points = [
    [pos[0] - 5, pos[1], pos[0] + 5, pos[1]],
    [pos[0], pos[1] - 5, pos[0], pos[1] + 5]

# general behavior for touch+move+release
for i, point in enumerate(points):
    x, y, nx, ny = point

    # create custom MotionEvent (touch) instance
    touch = UTMotionEvent("unittest", 1, {
        "sx": x / float(win.width),
        "sy": y / float(win.height),

The points and touch are ready. Let's dispatch the input in the test. For that we use EventLoop again and its method post_dispatch_input(event_type, motion_event).

  • touch down with begin event type
  • touch move with update event type
  • touch up with end event type
# dispatch the MotionEvent in EventLoop as
# touch/press/click, see Profiles for more info:
# https://kivy.org/docs/api-kivy.input.motionevent.html#profiles
EventLoop.post_dispatch_input("begin", touch)

# the touch is dispatched and has ud['lines']
# available from on_touch_down
self.assertIn('lines', touch.ud)
self.assertTrue(isinstance(touch.ud['lines'], Point))

# move touch from current to the new position
    "sx": nx / float(win.width),
    "sy": ny / float(win.height)
# update the MotionEvent in EventLoop
EventLoop.post_dispatch_input("update", touch)

# release the MotionEvent in EventLoop
EventLoop.post_dispatch_input("end", touch)

# still available, but released
self.assertIn('lines', touch.ud)
self.assertTrue(isinstance(touch.ud['lines'], Point))

expected_points = [[
    x + 0, y, x + 1, y,
    x + 2, y, x + 3, y,
    x + 4, y, x + 5, y,
    x + 6, y, x + 7, y,
    x + 8, y, x + 9, y
], [
    x, y + 0, x, y + 1,
    x, y + 2, x, y + 3,
    x, y + 4, x, y + 5,
    x, y + 6, x, y + 7,
    x, y + 8, x, y + 9

# check if the instruction points == expected ones

The less obvious part comes now, because we need to trigger the rendering of our graphics in the application. Fortunately that's easy to do with simple GraphicUnitTest.render(). You most likely want to put there the root widget like when building an application with App.build() method.

# render the graphics

It's quite useful to add unittest.main() at the end of your test, because if you only try to write a single test then you most likely don't want to run the whole suite. Especially if the suite is large.

if __name__ == '__main__':
    import unittest

Tips for testing

Handle class communication through App class via App.get_running_app() in your application, put every needed widget inside App class like this:

class MyButton(Button):
    def __init__(self, **kwargs):
        super(<class name>, self).__init__(**kwargs)
        self.text = 'Hello Test'
        app = App.get_running_app()
        app.my_button = self

and then access your widgets in test's run_test() function via app parameter like this:

self.assertEqual('Hello Test', app.my_button.text)

Use app.root to get instance of a class you pass in the build() function in the App class.

Dispatch events through widgets e.g. <widget>.dispatch('on_release') to execute function bound to on_release.

Use Kivy's Inspector module as help to navigate down the path of App class and use ids in kv language, it'll make targeting a specific widget easier.

Try even Kivy's Recorder module to record steps and play them later instead of dispatching events manually. However, this way is heavy time-consuming as it plays the steps exactly as long as they were recorded.


from kivy.input.recorder import Recorder

# place this inside ``run_test()``
rec = Recorder(filename='myrecorder.kvi')
rec.play = True

This will play all steps and then executes a function bound to on_stop. May be useful for testing touch gestures, swipes, dragging and other rather annoying to write manually stuff.

There's also possibility to change time the steps were recorded in in .kvi file (that long number), which will speed things up.

Also, there's a very interesting Python package made by Mathieu Virbel that allows you to go down the widget tree rabit hole in a more sane way than using this:


which gets tedious and annoying the more you use it when you navigate the tree from the application's root widget itself through complex layouts. This is where Telenium might save you a lot of minutes instead of typing the same thing over and over.


The MIT License (MIT)