Test variables


When Fuego executes a test, shell environment variables are used to provide information about the test environment, test execution parameters, communications methods and parameters, and other items.

These pieces of information are originate from numerous different places. An initial set of test variables comes in the shell environment from either Jenkins or from the shell in which ftc is executed (depending on which one is used to invoke the test).

The information about the board being tested comes primarily from two sources:

  • The board file

  • The stored board variables file

Additional information comes from the testplan and test spec that are used for this particular test run. Finally, test variables can be defined on the ftc command line. These test variables (know as dynamic variables, override variables that come from other sources.

Test variables can be simple strings, or they may be shell functions.

When a test is run, Fuego gathers information from all these sources, and makes them available to the test (and uses them itself) to control test execution.

Board file

The board file contains static information about a board. It is processed by the overlay system, and the values inside it appear as variables in the environment of a test, during test execution.

The board file resides in /fuego-ro/boards and the filename ends in the string “.board”:

  • /fuego-ro/boards/{board_name}.board

There are a number of variables which are used by the Fuego system itself, and there may also be variables that are used by individual tests.

Common board variables

Here is a list of the foo bar variables which might be found in a board file:

  • ARCHITECTURE - specifies the architecture of the board

  • BAUD - baud rate for serial device (if using ‘serial’ transport)

  • BOARD_TESTDIR - directory on board where tests are executed

  • BOARD_CONTROL - the mechanism used to control board hardware (e.g. hardware reboot)

  • DISTRIB - filename of distribution overlay file (if not the default)

  • IO_TIME_SERIAL - serial port delay parameter (if using ‘serial’ transport)

  • IPADDR - network address of the board

  • LOGIN - specifies the user account to use for Fuego operations

  • PASSWORD - specifies the password for the user account on the board used by Fuego

  • PLATFORM - specifies the toolchain to use for the platform

  • SATA_DEV - specifies a filesystem device node (on the board) for SATA filesystem tests

  • SATA_MP - specifies a filesystem mount point (on the board) for SATA filesystem tests

  • SERIAL - serial device on host for board’s serial console (if using ‘serial’ transport)

  • SRV_IP - network address of server endpoint, for networking tests (if not the same as the host)

  • SSH_KEY - the absolute path to key file with ssh key for password-less ssh operations (e.g. “/fuego-ro/board/myboard_id_rsa”)

  • SSH_PORT - network port of ssh daemon on board (if using ssh transport)

  • TRANSPORT - this specifies the transport to use with the target

  • USB_DEV - specifies a filesystem device node (on the board) for USB filesystem tests

  • USB_MP - specifies a filesystem mount point (on the board) for USB filesystem tests

See Adding a board for more details about these variables.

A board may also have additional variables, including variables that are used for results evaluation for specific tests.

Overlay system

The overlay system gathers variables from several places, and puts them all together into a single file which is then source’ed into the running test’s environment.

It takes information from:

  • The board files (both static and dynamic)

  • The testplan

  • The test spec

  • The overlay files

and combines them all, using a set of priorities, into a single file called prolog.sh, which is then source’ed into the running shell environment of the Fuego test being executed.

The overlay system is described in greater detail here: Overlay_Generation

Stored variables

Stored board variables are test variables that are defined on a per-board basis, and can be modified and managed under program control.

Stored variables allow the Fuego system, a test, or a user to store information that can be used by tests. This essentially creates an information cache about the board, that can be both manually and programmatically generated and managed.

The information that needs to be held for a particular board depends on the tests that are installed in the system. Thus the system needs to support ad-hoc collections of variables. Just putting everything into the static board file would not scale, as the number of tests increases.


The LAVA test framework has a similar concept called a board dictionary.

One use case for this to have a “board setup” test, that scans for lots of different items, and populates the stored variables with values that are used by other tests. Some items that are useful to know about a board take time to discover (using e.g. find on the target board), and using a board dynamic variable can help reduce the time required to check these items.

The board stored variables are kept in the file:
  • /fuego-rw/boards/{board_name}.vars

These variables are included in the test by the overlay generator.

Commands for interacting with stored variables

A user or a test can manipulate a board stored variable using the ftc command.The following commands can be used to set, query and delete variables:

  • tc query-board - to see test variables (both regular board variables and stored variables)

  • ftc set-var - to add or update a stored variable

  • ftc delete-var - to delete a stored variable

ftc query-board

ftc query-board is used to view the variables associated with a Fuego board. You can use the command to see all the variables, or just a single variable.

Note that ftc query-board shows the variables for a test that come from both the board file and board stored variables file (that is, both ‘static’ board variables and stored variables). It does not show variables which come from testplans or spec files, as those are specific to a test.

The usage is:
  • ftc query-board <board> [-n <VARIABLE>]


$ ftc query-board myboard
$ ftc query-board myboard -n PROGRAM_BC

The first example would show all board variables, including functions. The second example would show only the variable PROGRAM_BC, if it existed, for board ‘myboard’.

ftc set-var

ftc set-var allows setting or updating the value of a board stored variable.

The usage is:

  • ftc set-var <board> <VARIABLE>=<value>

By convention, variable names are all uppercase, and function names are lowercase, with words separated by underscores.


$ ftc set-var PROGRAM_BC=/usr/bin/bc

ftc delete-var

ftc delete-var removes a variable from the stored variables file.


$ ftc delete-var PROGRAM_BC

Example usage

The test Functional.fuego_board_check could detect the path for the foo binary, (e.g. is_on_target foo PROGRAM_FOO) and call ftc set-var $NODE_NAME PROGRAM_FOO=$PROGRAM_FOO. This would stay persistently defined as a test variable, so other tests could use $PROGRAM_FOO (with assert_define, or in report or cmd function calls.)

Example Stored variables

Here are some examples of variables that can be kept as stored variables, rather than static variables from the board file:

  • SATA_DEV = Linux device node for SATA file system tests

  • SATA_MP = Linux mount point for SATA file system tests

  • LTP_OPEN_POSIX_SUBTEST_COUNT_POS = expected number of pass results for LTP OpenPosix test

  • LTP_OPEN_POSIX_SUBTEST_COUNT_NEG = expected number of fail results for LTP OpenPosix test

  • PROGRAM_BC = path to ‘bc’ program on the target board

  • MAX_REBOOT_RETRIES = number of retries to use when rebooting a board

Spec variables

A test spec can define one or more variables to be used with a test. These are commonly used to control test variations, and are specified in a spec.json file.

When a spec file defines a variable associated with a named test spec, the variable is read by the overlay generator on test execution, and the variable name is prefixed with the name of the test, and converted to all upper case.

For example, support a test called Functional.foo had a test spec that defined the variable ‘args’ with a line like the following in its spec.json file:

"default": {
    "args": "-v -p2"

When the test was run with this spec (the “default” spec), then the variable FUNCTIONAL_FOO_ARGS would be defined, with the value “-v -p2”.

See Test_Specs_and_Plans for more information about specs and plans.

Dynamic variables

Another category of variables used during testing are dynamic variables. These variables are defined on the command line of ftc run-test using the --dynamic-vars option.

The purpose of these variables is to allow scripted variations when running ftc run-test The scripted variables are processed and presented the same way as spec variables, which is to say that the variable name is prefixed with the test name, and converted to all upper case.

For example, if the following command was issued:

  • ftc run-test -b beaglebone -t Functional.foo --dynamic_vars *ARGS=-p*

then during test execution the variable FUNCTIONAL_FOO_ARGS would be defined with the value “-p”.

See Dynamic Variables for more information.

Variable precedence

Here is the precedence of variable definition for Fuego, during test execution:

(from lowest to highest)
  1. environment variable (from Jenkins or shell where ‘ftc run-test’ is invoked)

  2. board variable (from fuego-ro/boards/$BOARD.board file)

  3. stored variable (from fuego-rw/boards/$BOARD.vars file)

  4. spec variable (from spec.json file)

  5. dynamic variable (from ftc command line)

  6. core variable (from Fuego scripts)

  7. fuego_test variable (from fuego_test.sh)

Spec and dynamic variables are prefixed with the test name, and converted to upper case. That tends to keep them in a separate name space from the rest of the test variables.