Setting up automated testing on a NUC using Yocto

This article describes how automated deployment can be set up for test automation of images on a HW-target directly from bitbake on the build host. Relevant upstream documentation is available in the Yocto docs for automated runtime testing

After following this how-to you should have:

  • An Intel NUC which is ready to use as testing target
  • Knowledge about how to get bitbake to deploy and run tests using that testing target

How it works

In order to facilitate the deployment of images to the NUC a "testmaster" image is used. The NUC is setup to boot this testmaster image by default, and then bitbake can deploy the target rootfs and target kernel using scp and some scripting.

The target rootfs is put on a separate partition, so the testmaster stays intact. Then the bootloader is told to boot a secondary entry called "test" once, and the target is rebooted which will cause it to boot using the rootfs and kernel that should be tested. The tests are then triggered using an ssh connection, and when all tests are done the target is rebooted once more so it ends up in testmaster image again.

There are hooks for enabling bitbake to power-cycle the NUC, which is required if the testing should be able to recover from e.g. images that doesn't boot. Without those hooks it depends on that a reboot can be initiated over an ssh connection. This how-to will not describe these hooks though.

Preparing the NUC

There is an image called core-image-testmaster which is used as a basis for the setup. Following are a number of manual steps that need to be performed when deploying this image. The repo tool is used in the examples, for more information see Using the repo tool

Start by building the image:

mkdir test-automation && cd test-automation
repo init -u -m pelux-intel-qtauto.xml -b master
repo sync
TEMPLATECONF=`pwd`/sources/meta-pelux-bsp-intel/conf-qt/ source sources/poky/oe-init-build-env build
echo 'EFI_PROVIDER = "systemd-boot"' >> conf/local.conf
bitbake core-image-testmaster

We will deploy this image to a USB-stick with the following partition scheme:

Partition # File system Label Comment
1 vfat boot  
2 ext3    
3 swap    
4 ext3 testrootfs Will be mounted by scripts, so need correct label

Instead of deploying directly to the USB-stick using we run mkefidisk on a file-backed loop-device in order to leave more space at the end of the disk for partition #4. Mkefidisk would otherwise grow the partition #2 as much as possible to fill the USB-stick.

Please note that the last argument to is the name of the device on the target HW, e.g. /dev/sda or /dev/mmcblk2, etc.

dd if=/dev/zero of=output.img count=1024 bs=4M
sudo losetup --find --show output.img
sudo ../sources/poky/scripts/contrib/ /dev/loop<NUMBER FROM PREVIOUS COMMAND> tmp/deploy/images/intel-corei7-64/core-image-testmaster-intel-corei7-64.hddimg /dev/sda
sudo losetup -d /dev/loop<NUMBER FROM PREVIOUS COMMAND>

We now have a 4GB big disk image which we can write to a USB-stick.

sudo dd if=output.img of=/dev/sd<YOUR USB DEVICE> bs=10M status=progress

When this is completed, remove and re-insert the USB-stick. Partition #1-3 will be created now, but we need to manually add partition #4.

sudo fdisk /dev/sd<YOUR USB DEVICE>
- Press n for new partition
- Press p for a primary partition
- Press enter twice to get it to fill all remaining space
- Press w to write
sudo mkfs.ext3 -L testrootfs /dev/sd<YOUR USB DEVICE>4

Now mount the testmaster rootfs in order to do some changes there:

sudo mount /dev/sd<YOUR USB DEVICE>2 /mnt/

# Create image used to identify if system is booted into the testmaster image
sudo touch /mnt/etc/masterimage

# Make sure the testmaster image shows a login prompt
sudo ln -sf /lib/systemd/system/getty@.service /mnt/etc/systemd/system/

# Create a network conf file which we then copy to rootfs, this one uses DHCP
cat <<EOF > /tmp/


sudo cp /tmp/ /mnt/etc/systemd/network/

# Unmount
sudo umount /mnt

Now we mount the EFI partition to add a bootloader entry called "test" which boots the kernel and file system under test.

# Set correct label on EFI partition
sudo dosfslabel /dev/sd<YOUR USB DEVICE>1 boot

# Mount EFI partition
sudo mount /dev/sd<YOUR USB DEVICE>1 /mnt/
# Create temp bootloader config file which we then copy
cat <<EOF > /tmp/test.conf
title test
linux /test-kernel
options LABEL=test root=/dev/sda4 ro rootwait console=ttyS0 console=tty0
sudo cp /tmp/test.conf /mnt/loader/entries/

# Unmount
sudo umount /mnt

The USB-stick should now be ready and can be inserted into a NUC and booted, do that and check what IP-address it gets using e.g. "ip a".

Building and testing an image

There is some configuration that needs to be setup in local.conf in order to enable target testing, so add the following to conf/local.conf

IMAGE_FSTYPES += "tar.gz"
INHERIT += "testimage"
TEST_TARGET = "SystemdbootTarget"
TEST_SERVER_IP = "<IP of machine used for building>"

Sometimes we need to set TEST_SERVER_IP, although that shouldn't be necessary according to the docs. This might be related to multiple network interfaces confusing the auto-detection.

You can now build and test basically any image using bitbake -c testimage <my image>, e.g.:

bitbake -c testimage core-image-pelux

Adding a new test

The unit tests run by bitbake when executing the testimage target of an image are Python scripts executed on the build machine. They rely on the standard unittest module and infrastructure but are extended by Yocto's oeqa module.

The unittest module of Python offers the basic testing capabilities. For instance, the TestCase class has an assertTrue(condition, message) method to verify whether a condition is true. This module is documented in the Python documentation.

The oeqa module extends unittest with additional features. For instance, the OERuntimeTestCase class has a method which can remotely trigger a command via SSH. Other functionalities include files copying or package management. This module is documented in the Yocto documentation.

Adding a new test can be done by creating a new .py file under the lib/oeqa/runtime/cases directory of any Yocto layer. For instance, let's create a minimal test case checking the output and status of the echo command. Put the following code into sources/meta-pelux/lib/oeqa/runtime/cases/

from import OERuntimeTestCase
from oeqa.core.decorator.depends import OETestDepends

class HelloTest(OERuntimeTestCase):
    def test_hello(self):
        (status, output) ="echo hello")
        self.assertTrue(status == 0,"'echo hello' did not return a 0 status")
        self.assertTrue(output == "hello", "'echo hello' did not show hello")

Bitbake can now find this test but it won't be executed by default. If you want your test to be ran, you need to set the TEST_SUITES variable in your local.conf. For instance, add the following line:

TEST_SUITES = "ping ssh hello"

Note that the order is important and that there might be dependencies between tests. Here, hello depends on ssh which depends on ping. Various examples of test cases can be found in sources/poky/meta/lib/oeqa/runtime/cases/.