test/py: fix spawn.expect multiple match handling

[people/ms/u-boot.git] / test / py / README.md

# U-Boot pytest suite

## Introduction

This tool aims to test U-Boot by executing U-Boot shell commands using the
console interface. A single top-level script exists to execute or attach to the
U-Boot console, run the entire script of tests against it, and summarize the
results. Advantages of this approach are:

- Testing is performed in the same way a user or script would interact with
  U-Boot; there can be no disconnect.
- There is no need to write or embed test-related code into U-Boot itself.
  It is asserted that writing test-related code in Python is simpler and more
  flexible that writing it all in C.
- It is reasonably simple to interact with U-Boot in this way.

## Requirements

The test suite is implemented using pytest. Interaction with the U-Boot console
involves executing some binary and interacting with its stdin/stdout. You will
need to implement various "hook" scripts that are called by the test suite at
the appropriate time.

On Debian or Debian-like distributions, the following packages are required.
Similar package names should exist in other distributions.

| Package        | Version tested (Ubuntu 14.04) |
| -------------- | ----------------------------- |
| python         | 2.7.5-5ubuntu3                |
| python-pytest  | 2.5.1-1                       |

The test script supports either:

- Executing a sandbox port of U-Boot on the local machine as a sub-process,
  and interacting with it over stdin/stdout.
- Executing an external "hook" scripts to flash a U-Boot binary onto a
  physical board, attach to the board's console stream, and reset the board.
  Further details are described later.

### Using `virtualenv` to provide requirements

Older distributions (e.g. Ubuntu 10.04) may not provide all the required
packages, or may provide versions that are too old to run the test suite. One
can use the Python `virtualenv` script to locally install more up-to-date
versions of the required packages without interfering with the OS installation.
For example:

```bash
$ cd /path/to/u-boot
$ sudo apt-get install python python-virtualenv
$ virtualenv venv
$ . ./venv/bin/activate
$ pip install pytest
```

## Testing sandbox

To run the testsuite on the sandbox port (U-Boot built as a native user-space
application), simply execute:

```
./test/py/test.py --bd sandbox --build
```

The `--bd` option tells the test suite which board type is being tested. This
lets the test suite know which features the board has, and hence exactly what
can be tested.

The `--build` option tells U-Boot to compile U-Boot. Alternatively, you may
omit this option and build U-Boot yourself, in whatever way you choose, before
running the test script.

The test script will attach to U-Boot, execute all valid tests for the board,
then print a summary of the test process. A complete log of the test session
will be written to `${build_dir}/test-log.html`. This is best viewed in a web
browser, but may be read directly as plain text, perhaps with the aid of the
`html2text` utility.

## Command-line options

- `--board-type`, `--bd`, `-B` set the type of the board to be tested. For
  example, `sandbox` or `seaboard`.
- `--board-identity`, `--id` set the identity of the board to be tested.
  This allows differentiation between multiple instances of the same type of
  physical board that are attached to the same host machine. This parameter is
  not interpreted by the test script in any way, but rather is simply passed
  to the hook scripts described below, and may be used in any site-specific
  way deemed necessary.
- `--build` indicates that the test script should compile U-Boot itself
  before running the tests. If using this option, make sure that any
  environment variables required by the build process are already set, such as
  `$CROSS_COMPILE`.
- `--build-dir` sets the directory containing the compiled U-Boot binaries.
  If omitted, this is `${source_dir}/build-${board_type}`.
- `--result-dir` sets the directory to write results, such as log files,
  into. If omitted, the build directory is used.
- `--persistent-data-dir` sets the directory used to store persistent test
  data. This is test data that may be re-used across test runs, such as file-
  system images.

`pytest` also implements a number of its own command-line options. Please see
`pytest` documentation for complete details. Execute `py.test --version` for
a brief summary. Note that U-Boot's test.py script passes all command-line
arguments directly to `pytest` for processing.

## Testing real hardware

The tools and techniques used to interact with real hardware will vary
radically between different host and target systems, and the whims of the user.
For this reason, the test suite does not attempt to directly interact with real
hardware in any way. Rather, it executes a standardized set of "hook" scripts
via `$PATH`. These scripts implement certain actions on behalf of the test
suite. This keeps the test suite simple and isolated from system variances
unrelated to U-Boot features.

### Hook scripts

#### Environment variables

The following environment variables are set when running hook scripts:

- `UBOOT_BOARD_TYPE` the board type being tested.
- `UBOOT_BOARD_IDENTITY` the board identity being tested, or `na` if none was
  specified.
- `UBOOT_SOURCE_DIR` the U-Boot source directory.
- `UBOOT_TEST_PY_DIR` the full path to `test/py/` in the source directory.
- `UBOOT_BUILD_DIR` the U-Boot build directory.
- `UBOOT_RESULT_DIR` the test result directory.
- `UBOOT_PERSISTENT_DATA_DIR` the test peristent data directory.

#### `u-boot-test-console`

This script provides access to the U-Boot console. The script's stdin/stdout
should be connected to the board's console. This process should continue to run
indefinitely, until killed. The test suite will run this script in parallel
with all other hooks.

This script may be implemented e.g. by exec()ing `cu`, `kermit`, `conmux`, etc.

If you are able to run U-Boot under a hardware simulator such as qemu, then
you would likely spawn that simulator from this script. However, note that
`u-boot-test-reset` may be called multiple times per test script run, and must
cause U-Boot to start execution from scratch each time. Hopefully your
simulator includes a virtual reset button! If not, you can launch the
simulator from `u-boot-test-reset` instead, while arranging for this console
process to always communicate with the current simulator instance.

#### `u-boot-test-flash`

Prior to running the test suite against a board, some arrangement must be made
so that the board executes the particular U-Boot binary to be tested. Often,
this involves writing the U-Boot binary to the board's flash ROM. The test
suite calls this hook script for that purpose.

This script should perform the entire flashing process synchronously; the
script should only exit once flashing is complete, and a board reset will
cause the newly flashed U-Boot binary to be executed.

It is conceivable that this script will do nothing. This might be useful in
the following cases:

- Some other process has already written the desired U-Boot binary into the
  board's flash prior to running the test suite.
- The board allows U-Boot to be downloaded directly into RAM, and executed
  from there. Use of this feature will reduce wear on the board's flash, so
  may be preferable if available, and if cold boot testing of U-Boot is not
  required. If this feature is used, the `u-boot-test-reset` script should
  peform this download, since the board could conceivably be reset multiple
  times in a single test run.

It is up to the user to determine if those situations exist, and to code this
hook script appropriately.

This script will typically be implemented by calling out to some SoC- or
board-specific vendor flashing utility.

#### `u-boot-test-reset`

Whenever the test suite needs to reset the target board, this script is
executed. This is guaranteed to happen at least once, prior to executing the
first test function. If any test fails, the test infra-structure will execute
this script again to restore U-Boot to an operational state before running the
next test function.

This script will likely be implemented by communicating with some form of
relay or electronic switch attached to the board's reset signal.

The semantics of this script require that when it is executed, U-Boot will
start running from scratch. If the U-Boot binary to be tested has been written
to flash, pulsing the board's reset signal is likely all this script need do.
However, in some scenarios, this script may perform other actions. For
example, it may call out to some SoC- or board-specific vendor utility in order
to download the U-Boot binary directly into RAM and execute it. This would
avoid the need for `u-boot-test-flash` to actually write U-Boot to flash, thus
saving wear on the flash chip(s).

### Board-type-specific configuration

Each board has a different configuration and behaviour. Many of these
differences can be automatically detected by parsing the `.config` file in the
build directory. However, some differences can't yet be handled automatically.

For each board, an optional Python module `u_boot_board_${board_type}` may exist
to provide board-specific information to the test script. Any global value
defined in these modules is available for use by any test function. The data
contained in these scripts must be purely derived from U-Boot source code.
Hence, these configuration files are part of the U-Boot source tree too.

### Execution environment configuration

Each user's hardware setup may enable testing different subsets of the features
implemented by a particular board's configuration of U-Boot. For example, a
U-Boot configuration may support USB device mode and USB Mass Storage, but this
can only be tested if a USB cable is connected between the board and the host
machine running the test script.

For each board, optional Python modules `u_boot_boardenv_${board_type}` and
`u_boot_boardenv_${board_type}_${board_identity}` may exist to provide
board-specific and board-identity-specific information to the test script. Any
global value defined in these modules is available for use by any test
function. The data contained in these is specific to a particular user's
hardware configuration. Hence, these configuration files are not part of the
U-Boot source tree, and should be installed outside of the source tree. Users
should set `$PYTHONPATH` prior to running the test script to allow these
modules to be loaded.

### Board module parameter usage

The test scripts rely on the following variables being defined by the board
module:

- None at present.

### U-Boot `.config` feature usage

The test scripts rely on various U-Boot `.config` features, either directly in
order to test those features, or indirectly in order to query information from
the running U-Boot instance in order to test other features.

One example is that testing of the `md` command requires knowledge of a RAM
address to use for the test. This data is parsed from the output of the
`bdinfo` command, and hence relies on CONFIG_CMD_BDI being enabled.

For a complete list of dependencies, please search the test scripts for
instances of:

- `buildconfig.get(...`
- `@pytest.mark.buildconfigspec(...`

### Complete invocation example

Assuming that you have installed the hook scripts into $HOME/ubtest/bin, and
any required environment configuration Python modules into $HOME/ubtest/py,
then you would likely invoke the test script as follows:

If U-Boot has already been built:

```bash
PATH=$HOME/ubtest/bin:$PATH \
    PYTHONPATH=${HOME}/ubtest/py:${PYTHONPATH} \
    ./test/py/test.py --bd seaboard
```

If you want the test script to compile U-Boot for you too, then you likely
need to set `$CROSS_COMPILE` to allow this, and invoke the test script as
follow:

```bash
CROSS_COMPILE=arm-none-eabi- \
    PATH=$HOME/ubtest/bin:$PATH \
    PYTHONPATH=${HOME}/ubtest/py:${PYTHONPATH} \
    ./test/py/test.py --bd seaboard --build
```

## Writing tests

Please refer to the pytest documentation for details of writing pytest tests.
Details specific to the U-Boot test suite are described below.

A test fixture named `u_boot_console` should be used by each test function. This
provides the means to interact with the U-Boot console, and retrieve board and
environment configuration information.

The function `u_boot_console.run_command()` executes a shell command on the
U-Boot console, and returns all output from that command. This allows
validation or interpretation of the command output. This function validates
that certain strings are not seen on the U-Boot console. These include shell
error messages and the U-Boot sign-on message (in order to detect unexpected
board resets). See the source of `u_boot_console_base.py` for a complete list of
"bad" strings. Some test scenarios are expected to trigger these strings. Use
`u_boot_console.disable_check()` to temporarily disable checking for specific
strings. See `test_unknown_cmd.py` for an example.

Board- and board-environment configuration values may be accessed as sub-fields
of the `u_boot_console.config` object, for example
`u_boot_console.config.ram_base`.

Build configuration values (from `.config`) may be accessed via the dictionary
`u_boot_console.config.buildconfig`, with keys equal to the Kconfig variable
names.