libfprint/tests/README.md

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`umockdev` Tests
================
`umockdev` tests use fingerprint devices mocked by [`umockdev`
toolchain][umockdev].
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).
[umockdev]: https://github.com/martinpitt/umockdev