libfprint/tests

umockdev Tests

umockdev tests use fingerprint devices mocked by umockdev toolchain.

This document describes how to create a 'capture' test: a test that captures a picture of a fingerprint from the device (mocked by umockdev) and compares it with the standard one.

Other kinds of umockdev tests can be created in a similar manner. For match-on-chip devices you would instead create a test specific custom.py script, capture it and store the capture to custom.pcapng.

'Capture' Test Creation

A new 'capture' test is created by means of capture.py script:

1. Create (if needed) a directory for the driver under tests directory:

   mkdir DRIVER

   Note that the name must be the exact name of the libfprint driver, or the exact name of the driver followed by a - and a unique identifier of your choosing.

2. Prepare your execution environment.

   In the next step a working and up to date libfprint is needed. This can be achieved by installing it into your system. Alternatively, you can set the following environment variables to run a local build:

   • export LD_PRELOAD=<meson-build-dir>/libfprint/libfprint-2.so
   • export GI_TYPELIB_PATH=<meson-build-dir>/libfprint

   Also, sometimes the driver must be adapted to the emulated environment (mainly if it uses random numbers, see synaptics.c for an example). Set the following environment variable to enable this adaptation:

   • export FP_DEVICE_EMULATION=1

   Run the next steps in the same terminal.

3. Find the real USB fingerprint device with lsusb, e.g.:

   Bus 001 Device 005: ID 138a:0090 Validity Sensors, Inc. VFS7500 Touch Fingerprint Sensor

   The following USB device is used in the example above: /dev/bus/usb/001/005.

   For the following commands, it is assumed that the user that's running the commands has full access to the device node, whether by running the commands as root, or changing the permissions for that device node.

4. Record information about this device:

   umockdev-record /dev/bus/usb/001/005 > DRIVER/device

5. Record interaction of capture.py (or other test) with the device. To do so, start wireshark and record usbmonX (where X is the bus number). Then run the test script:

   python3 ./capture.py DRIVER/capture.png

   Save the wireshark recording as capture.pcapng. The command will create capture.png.

6. Add driver's name to drivers_tests in the meson.build.

7. Check whether everything works as expected.

Note. To avoid submitting a real fingerprint, the side of finger, arm, or anything else producing an image with the device can be used.

Possible Issues

Other changes may be needed to get everything working. For example the elan driver relies on a timeout that is not reported correctly. In this case the driver works around it by interpreting the protocol error differently in the virtual environment (by means of FP_DEVICE_EMULATION environment variable).