Writing Avocado Tests with Python

We are going to write an Avocado test in Python and we are going to inherit from avocado.Test. This makes this test a so-called instrumented test.

Basic example

Let’s re-create an old time favorite, sleeptest [1]. It is so simple, it does nothing besides sleeping for a while:

import time

from avocado import Test

class SleepTest(Test):

    def test(self):
        sleep_length = self.params.get('sleep_length', default=1)
        self.log.debug("Sleeping for %.2f seconds", sleep_length)
        time.sleep(sleep_length)

This is about the simplest test you can write for Avocado, while still leveraging its API power.

As can be seen in the example above, an Avocado test is a method that starts with test in a class that inherits from avocado.Test.

Multiple tests and naming conventions

You can have multiple tests in a single class.

To do so, just give the methods names that start with test, say test_foo, test_bar and so on. We recommend you follow this naming style, as defined in the PEP8 Function Names section.

For the class name, you can pick any name you like, but we also recommend that it follows the CamelCase convention, also known as CapWords, defined in the PEP 8 document under Class Names.

Convenience Attributes

Note that the test class provides you with a number of convenience attributes:

  • A ready to use log mechanism for your test, that can be accessed by means of self.log. It lets you log debug, info, error and warning messages.
  • A parameter passing system (and fetching system) that can be accessed by means of self.params. This is hooked to the Varianter, about which you can find that more information at TestParameters.
  • And many more (see avocado.core.test.Test)

To minimize the accidental clashes we define the public ones as properties so if you see something like AttributeError: can't set attribute double you are not overriding these.

Test statuses

Avocado supports the most common exit statuses:

  • PASS - test passed, there were no untreated exceptions
  • WARN - a variant of PASS that keeps track of noteworthy events that ultimately do not affect the test outcome. An example could be soft lockup present in the dmesg output. It’s not related to the test results and unless there are failures in the test it means the feature probably works as expected, but there were certain condition which might be nice to review. (some result plugins does not support this and report PASS instead)
  • SKIP - the test’s pre-requisites were not satisfied and the test’s body was not executed (nor its setUp() and tearDown).
  • CANCEL - the test was canceled somewhere during the setUp(), the test method or the tearDown(). The setUp() and tearDown methods are executed.
  • FAIL - test did not result in the expected outcome. A failure points at a (possible) bug in the tested subject, and not in the test itself. When the test (and its) execution breaks, an ERROR and not a FAIL is reported.”
  • ERROR - this points (probably) at a bug in the test itself, and not in the subject being tested.It is usually caused by uncaught exception and such failures needs to be thoroughly explored and should lead to test modification to avoid this failure or to use self.fail along with description how the subject under testing failed to perform it’s task.
  • INTERRUPTED - this result can’t be set by the test writer, it is only possible when the timeout is reached or when the user hits CTRL+C while executing this test.
  • other - there are some other internal test statuses, but you should not ever face them.

As you can see the FAIL is a neat status, if tests are developed correctly. When writing tests always think about what its setUp should be, what the test body and is expected to go wrong in the test. To support you Avocado supports several methods:

Test methods

The simplest way to set the status is to use self.fail, self.error or self.cancel directly from test.

To remember a warning, one simply writes to self.log.warning logger. This won’t interrupt the test execution, but it will remember the condition and, if there are no failures, will report the test as WARN.

Turning errors into failures

Errors on Python code are commonly signaled in the form of exceptions being thrown. When Avocado runs a test, any unhandled exception will be seen as a test ERROR, and not as a FAIL.

Still, it’s common to rely on libraries, which usually raise custom (or builtin) exceptions. Those exceptions would normally result in ERROR but if you are certain this is an odd behavior of the object under testing, you should catch the exception and explain the failure in self.fail method:

try:
    process.run("stress_my_feature")
except process.CmdError as details:
    self.fail("The stress comamnd failed: %s" % details)

If your test compounds of many executions and you can’t get this exception in other case then expected failure, you can simplify the code by using fail_on decorator:

@avocado.fail_on(process.CmdError)
def test(self):
    process.run("first cmd")
    process.run("second cmd")
    process.run("third cmd")

Once again, keeping your tests up-to-date and distinguishing between FAIL and ERROR will save you a lot of time while reviewing the test results.

Turning errors into cancels

It is also possible to assume unhandled exception to be as a test CANCEL instead of a test ERROR simply by using cancel_on decorator:

def test(self):
    @avocado.cancel_on(TypeError)
    def foo():
        raise TypeError
    foo()

Saving test generated (custom) data

Each test instance provides a so called whiteboard. It can be accessed through self.whiteboard. This whiteboard is simply a string that will be automatically saved to test results after the test finishes (it’s not synced during the execution so when the machine or Python crashes badly it might not be present and one should use direct io to the outputdir for critical data). If you choose to save binary data to the whiteboard, it’s your responsibility to encode it first (base64 is the obvious choice).

Building on the previously demonstrated sleeptest, suppose that you want to save the sleep length to be used by some other script or data analysis tool:

def test(self):
    sleep_length = self.params.get('sleep_length', default=1)
    self.log.debug("Sleeping for %.2f seconds", sleep_length)
    time.sleep(sleep_length)
    self.whiteboard = "%.2f" % sleep_length

The whiteboard can and should be exposed by files generated by the available test result plugins. The results.json file already includes the whiteboard for each test. Additionally, we’ll save a raw copy of the whiteboard contents on a file named whiteboard, in the same level as the results.json file, for your convenience (maybe you want to use the result of a benchmark directly with your custom made scripts to analyze that particular benchmark result).

If you need to attach several output files, you can also use self.outputdir, which points to the $RESULTS/test-results/$TEST_ID/data location and is reserved for arbitrary test result data.

Accessing test data files

Some tests can depend on data files, external to the test file itself. Avocado provides a test API that makes it really easy to access such files: get_data().

For Avocado tests (that is, INSTRUMENTED tests) get_data() allows test data files to be accessed from up to three sources:

  • file level data directory: a directory named after the test file, but ending with .data. For a test file /home/user/test.py, the file level data directory is /home/user/test.py.data/.
  • test level data directory: a directory named after the test file and the specific test name. These are useful when different tests part of the same file need different data files (with the same name or not). Considering the previous example of /home/user/test.py, and supposing it contains two tests, MyTest.test_foo and MyTest.test_bar, the test level data directories will be, /home/user/test.py.data/MyTest.test_foo/ and home/user/test.py.data/MyTest.test_bar/ respectively.
  • variant level data directory: if variants are being used during the test execution, a directory named after the variant will also be considered when looking for test data files. For test file /home/user/test.py, and test MyTest.test_foo, with variant debug-ffff, the data directory path will be /home/user/test.py.data/MyTest.test_foo/debug-ffff/.

Note

Unlike INSTRUMENTED tests, SIMPLE tests only define file and variant data_dirs, therefore the most-specific data-dir might look like /bin/echo.data/debug-ffff/.

Avocado looks for data files in the order defined at DATA_SOURCES, which are from most specific one, to most generic one. That means that, if a variant is being used, the variant directory is used first. Then the test level directory is attempted, and finally the file level directory. Additionally you can use get_data(filename, must_exist=False) to get expected location of a possibly non-existing file, which is useful when you intend to create it.

Tip

When running tests you can use the --log-test-data-directories command line option log the test data directories that will be used for that specific test and execution conditions (such as with or without variants). Look for “Test data directories” in the test logs.

Note

The previously existing API avocado.core.test.Test.datadir, used to allow access to the data directory based on the test file location only. This API has been removed. If, for whatever reason you still need to access the data directory based on the test file location only, you can use get_data(filename='', source='file', must_exist=False) instead.

Accessing test parameters

Each test has a set of parameters that can be accessed through self.params.get($name, $path=None, $default=None) where:

  • name - name of the parameter (key)
  • path - where to look for this parameter (when not specified uses mux-path)
  • default - what to return when param not found

The path is a bit tricky. Avocado uses tree to represent parameters. In simple scenarios you don’t need to worry and you’ll find all your values in default path, but eventually you might want to check-out TestParameters to understand the details.

Let’s say your test receives following params (you’ll learn how to execute them in the following section):

$ avocado variants -m examples/tests/sleeptenmin.py.data/sleeptenmin.yaml --variants 2
...
Variant 1:    /run/sleeptenmin/builtin, /run/variants/one_cycle
    /run/sleeptenmin/builtin:sleep_method => builtin
    /run/variants/one_cycle:sleep_cycles  => 1
    /run/variants/one_cycle:sleep_length  => 600
...

In test you can access those params by:

self.params.get("sleep_method")    # returns "builtin"
self.params.get("sleep_cycles", '*', 10)    # returns 1
self.params.get("sleep_length", "/*/variants/*"  # returns 600

Note

The path is important in complex scenarios where clashes might occur, because when there are multiple values with the same key matching the query Avocado raises an exception. As mentioned you can avoid those by using specific paths or by defining custom mux-path which allows specifying resolving hierarchy. More details can be found in TestParameters.

Running multiple variants of tests

In the previous section we described how parameters are handled. Now, let’s have a look at how to produce them and execute your tests with different parameters.

The variants subsystem is what allows the creation of multiple variations of parameters, and the execution of tests with those parameter variations. This subsystem is pluggable, so you might use custom plugins to produce variants. To keep things simple, let’s use Avocado’s primary implementation, called “yaml_to_mux”.

The “yaml_to_mux” plugin accepts YAML files. Those will create a tree-like structure, store the variables as parameters and use custom tags to mark locations as “multiplex” domains.

Let’s use examples/tests/sleeptenmin.py.data/sleeptenmin.yaml file as an example:

sleeptenmin: !mux
    builtin:
        sleep_method: builtin
    shell:
        sleep_method: shell
variants: !mux
    one_cycle:
        sleep_cycles: 1
        sleep_length: 600
    six_cycles:
        sleep_cycles: 6
        sleep_length: 100
    one_hundred_cycles:
        sleep_cycles: 100
        sleep_length: 6
    six_hundred_cycles:
        sleep_cycles: 600
        sleep_length: 1

Which produces following structure and parameters:

$ avocado variants -m examples/tests/sleeptenmin.py.data/sleeptenmin.yaml --summary 2 --variants 2
Multiplex tree representation:
 ┗━━ run
      ┣━━ sleeptenmin
      ┃    ╠══ builtin
      ┃    ║     → sleep_method: builtin
      ┃    ╚══ shell
      ┃          → sleep_method: shell
      ┗━━ variants
           ╠══ one_cycle
           ║     → sleep_length: 600
           ║     → sleep_cycles: 1
           ╠══ six_cycles
           ║     → sleep_length: 100
           ║     → sleep_cycles: 6
           ╠══ one_hundred_cycles
           ║     → sleep_length: 6
           ║     → sleep_cycles: 100
           ╚══ six_hundred_cycles
                 → sleep_length: 1
                 → sleep_cycles: 600

Multiplex variants (8):

Variant builtin-one_cycle-f659:    /run/sleeptenmin/builtin, /run/variants/one_cycle
    /run/sleeptenmin/builtin:sleep_method => builtin
    /run/variants/one_cycle:sleep_cycles  => 1
    /run/variants/one_cycle:sleep_length  => 600

Variant builtin-six_cycles-723b:    /run/sleeptenmin/builtin, /run/variants/six_cycles
    /run/sleeptenmin/builtin:sleep_method => builtin
    /run/variants/six_cycles:sleep_cycles => 6
    /run/variants/six_cycles:sleep_length => 100

Variant builtin-one_hundred_cycles-633a:    /run/sleeptenmin/builtin, /run/variants/one_hundred_cycles
    /run/sleeptenmin/builtin:sleep_method         => builtin
    /run/variants/one_hundred_cycles:sleep_cycles => 100
    /run/variants/one_hundred_cycles:sleep_length => 6

Variant builtin-six_hundred_cycles-a570:    /run/sleeptenmin/builtin, /run/variants/six_hundred_cycles
    /run/sleeptenmin/builtin:sleep_method         => builtin
    /run/variants/six_hundred_cycles:sleep_cycles => 600
    /run/variants/six_hundred_cycles:sleep_length => 1

Variant shell-one_cycle-55f5:    /run/sleeptenmin/shell, /run/variants/one_cycle
    /run/sleeptenmin/shell:sleep_method  => shell
    /run/variants/one_cycle:sleep_cycles => 1
    /run/variants/one_cycle:sleep_length => 600

Variant shell-six_cycles-9e23:    /run/sleeptenmin/shell, /run/variants/six_cycles
    /run/sleeptenmin/shell:sleep_method   => shell
    /run/variants/six_cycles:sleep_cycles => 6
    /run/variants/six_cycles:sleep_length => 100

Variant shell-one_hundred_cycles-586f:    /run/sleeptenmin/shell, /run/variants/one_hundred_cycles
    /run/sleeptenmin/shell:sleep_method           => shell
    /run/variants/one_hundred_cycles:sleep_cycles => 100
    /run/variants/one_hundred_cycles:sleep_length => 6

Variant shell-six_hundred_cycles-1e84:    /run/sleeptenmin/shell, /run/variants/six_hundred_cycles
    /run/sleeptenmin/shell:sleep_method           => shell
    /run/variants/six_hundred_cycles:sleep_cycles => 600
    /run/variants/six_hundred_cycles:sleep_length => 1

You can see that it creates all possible variants of each multiplex domain, which are defined by !mux tag in the YAML file and displayed as single lines in tree view (compare to double lines which are individual nodes with values). In total it’ll produce 8 variants of each test:

$ avocado run --mux-yaml examples/tests/sleeptenmin.py.data/sleeptenmin.yaml -- passtest.py
JOB ID     : cc7ef22654c683b73174af6f97bc385da5a0f02f
JOB LOG    : $HOME/avocado/job-results/job-2017-01-22T11.26-cc7ef22/job.log
 (1/8) passtest.py:PassTest.test;builtin-one_cycle-f659: PASS (0.01 s)
 (2/8) passtest.py:PassTest.test;builtin-six_cycles-723b: PASS (0.01 s)
 (3/8) passtest.py:PassTest.test;builtin-one_hundred_cycles-633a: PASS (0.01 s)
 (4/8) passtest.py:PassTest.test;builtin-six_hundred_cycles-a570: PASS (0.01 s)
 (5/8) passtest.py:PassTest.test;shell-one_cycle-55f5: PASS (0.01 s)
 (6/8) passtest.py:PassTest.test;shell-six_cycles-9e23: PASS (0.01 s)
 (7/8) passtest.py:PassTest.test;shell-one_hundred_cycles-586f: PASS (0.01 s)
 (8/8) passtest.py:PassTest.test;shell-six_hundred_cycles-1e84: PASS (0.01 s)
RESULTS    : PASS 8 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0
JOB TIME   : 0.16 s

There are other options to influence the params so please check out avocado run -h and for details use TestParameters.

unittest.TestCase heritage

Since an Avocado test inherits from unittest.TestCase, you can use all the assertion methods that its parent.

The code example bellow uses assertEqual, assertTrue and assertIsInstace:

from avocado import Test

class RandomExamples(Test):
    def test(self):
        self.log.debug("Verifying some random math...")
        four = 2 * 2
        four_ = 2 + 2
        self.assertEqual(four, four_, "something is very wrong here!")

        self.log.debug("Verifying if a variable is set to True...")
        variable = True
        self.assertTrue(variable)

        self.log.debug("Verifying if this test is an instance of test.Test")
        self.assertIsInstance(self, test.Test)

Running tests under other unittest runners

nose is another Python testing framework that is also compatible with unittest.

Because of that, you can run Avocado tests with the nosetests application:

$ nosetests examples/tests/sleeptest.py
.
----------------------------------------------------------------------
Ran 1 test in 1.004s

OK

Conversely, you can also use the standard unittest.main() entry point to run an Avocado test. Check out the following code, to be saved as dummy.py:

from avocado import Test
from unittest import main

class Dummy(Test):
    def test(self):
        self.assertTrue(True)

if __name__ == '__main__':
    main()

It can be run by:

$ python dummy.py
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

But we’d still recommend using avocado.main instead which is our main entry point.

Setup and cleanup methods

To perform setup actions before/after your test, you may use setUp and tearDown methods. The tearDown method is always executed even on setUp failure so don’t forget to initialize your variables early in the setUp. Example of usage is in the next section Running third party test suites.

Running third party test suites

It is very common in test automation workloads to use test suites developed by third parties. By wrapping the execution code inside an Avocado test module, you gain access to the facilities and API provided by the framework. Let’s say you want to pick up a test suite written in C that it is in a tarball, uncompress it, compile the suite code, and then executing the test. Here’s an example that does that:

import os

from avocado import Test
from avocado.utils import archive
from avocado.utils import build
from avocado.utils import process


class SyncTest(Test):

    """
    Execute the synctest test suite.
    """
    def setUp(self):
        """
        Set attributes from params and build the synctest suite.
        """
        sync_tarball = self.params.get('sync_tarball',
                                       default='synctest.tar.bz2')
        self.sync_length = self.params.get('sync_length', default=100)
        self.sync_loop = self.params.get('sync_loop', default=10)
        # Build the synctest suite
        self.cwd = os.getcwd()
        tarball_path = self.get_data(sync_tarball)
        archive.extract(tarball_path, self.workdir)
        self.workdir = os.path.join(self.workdir, 'synctest')
        build.make(self.workdir)

    def test(self):
        """
        Execute synctest with the appropriate params.
        """
        os.chdir(self.workdir)
        cmd = ('./synctest %s %s' %
               (self.sync_length, self.sync_loop))
        process.system(cmd)
        os.chdir(self.cwd)

Here we have an example of the setUp method in action: Here we get the location of the test suite code (tarball) through avocado.Test.get_data(), then uncompress the tarball through avocado.utils.archive.extract(), an API that will decompress the suite tarball, followed by avocado.utils.build.make(), that will build the suite.

In this example, the test method just gets into the base directory of the compiled suite and executes the ./synctest command, with appropriate parameters, using avocado.utils.process.system().

Fetching asset files

To run third party test suites as mentioned above, or for any other purpose, we offer an asset fetcher as a method of Avocado Test class. The asset fetch method looks for a list of directories in the cache_dirs key, inside the [datadir.paths] section from the configuration files. Read-only directories are also supported. When the asset file is not present in any of the provided directories, Avocado will try to download the file from the provided locations, copying it to the first writable cache directory. Example:

cache_dirs = ['/usr/local/src/', '~/avocado/data/cache']

In the example above, /usr/local/src/ is a read-only directory. In that case, when Avocado needs to fetch the asset from the locations, the asset will be copied to the ~/avocado/data/cache directory.

If the tester does not provide a cache_dirs for the test execution, Avocado creates a cache directory inside the Avocado data_dir location to put the fetched files in.

  • Use case 1: no cache_dirs key in config files, only the asset name provided in the full URL format:

    ...
        def setUp(self):
            stress = 'https://fossies.org/linux/privat/stress-1.0.4.tar.gz'
            tarball = self.fetch_asset(stress)
            archive.extract(tarball, self.workdir)
    ...
    

    In this case, fetch_asset() will download the file from the URL provided, copying it to the $data_dir/cache directory. The fetch_asset() method returns the target location of the fetched asset. In this example, the tarball variable holds /home/user/avocado/data/cache/stress-1.0.4.tar.gz.

  • Use case 2: Read-only cache directory provided. cache_dirs = ['/mnt/files']:

    ...
        def setUp(self):
            stress = 'https://fossies.org/linux/privat/stress-1.0.4.tar.gz'
            tarball = self.fetch_asset(stress)
            archive.extract(tarball, self.workdir)
    ...
    

    In this case, Avocado tries to find stress-1.0.4.tar.gz file in /mnt/files directory. If it’s not found, since /mnt/files cache is read-only, Avocado tries to download the asset file to the $data_dir/cache directory.

  • Use case 3: Writable cache directory provided, along with a list of locations. Use of the default cache directory, cache_dirs = ['~/avocado/data/cache']:

    ...
        def setUp(self):
            st_name = 'stress-1.0.4.tar.gz'
            st_hash = 'e1533bc704928ba6e26a362452e6db8fd58b1f0b'
            st_loc = ['https://fossies.org/linux/privat/stress-1.0.4.tar.gz',
                      'ftp://foo.bar/stress-1.0.4.tar.gz']
            tarball = self.fetch_asset(st_name, asset_hash=st_hash,
                                       locations=st_loc)
            archive.extract(tarball, self.workdir)
    ...
    

    In this case, Avocado tries to download stress-1.0.4.tar.gz from the provided locations list (if it’s not already in the default cache, ~/avocado/data/cache). As the hash was also provided, Avocado verifies the hash. To do so, Avocado first looks for a hash file named stress-1.0.4.tar.gz.CHECKSUM in the same directory. If the hash file is not available, Avocado computes the hash and creates the hash file for later use.

    The resulting tarball variable content will be ~/avocado/cache/stress-1.0.4.tar.gz. An exception is raised if Avocado fails to download or to verify the file.

  • Use case 4: Low bandwidth available for download of a large file which takes a lot of time to download and causes a CI, like Travis, for example, to timeout the test execution. Do not cancel the test if the file is not available:

    ...
        def setUp(self):
            st_name = 'stress-1.0.4.tar.gz'
            st_hash = 'e1533bc704928ba6e26a362452e6db8fd58b1f0b'
            st_loc = ['https://fossies.org/linux/privat/stress-1.0.4.tar.gz',
                      'ftp://foo.bar/stress-1.0.4.tar.gz']
            tarball = self.fetch_asset(st_name, asset_hash=st_hash,
                                       locations=st_loc, find_only=True)
            archive.extract(tarball, self.workdir)
    ...
    

    Setting the find_only parameter to True will make Avocado look for the asset in the cache, but will not attempt to download it if the asset is not available. The asset download can be done prior to the test execution using the command-line avocado assets fetch INSTRUMENTED.

    In this example, if the asset is not available in the cache, the test will continue to run and when the test tries to use the asset, it will fail. A solution for that is presented in the next use case.

  • Use case 5: Low bandwidth available for download or a large file which takes a lot of time to download and causes a CI, like Travis, for example, to timeout the test execution. Cancel the test if the file is not available:

    ...
        def setUp(self):
            st_name = 'stress-1.0.4.tar.gz'
            st_hash = 'e1533bc704928ba6e26a362452e6db8fd58b1f0b'
            st_loc = ['https://fossies.org/linux/privat/stress-1.0.4.tar.gz',
                      'ftp://foo.bar/stress-1.0.4.tar.gz']
            tarball = self.fetch_asset(st_name, asset_hash=st_hash,
                                       locations=st_loc, find_only=True,
                                       cancel_on_missing=True)
            archive.extract(tarball, self.workdir)
    ...
    

    With cancel_on_missing set to True and find_only set to True, if the file is not available in the cache, the test is canceled.

Detailing the fetch_asset() parameters:

  • name: The destination name used to the fetched file. It can also contains a full URI. The URI will be used as the location (after searching into the cache directories).
  • asset_hash: (optional) The expected hash for the file. If missing, Avocado skips the hash check. If provided, before computing the hash, Avocado looks for a hash file to verify the asset. If the hash file is not available, Avocado computes the hash and creates the hash file in the same cache directory for later use.
  • algorithm: (optional) Provided hash algorithm format. Defaults to sha1.
  • locations: (optional) List of locations used to try to fetch the file. The supported schemes are http://, https://, ftp:// and file://. The tester should inform the full url to the file, including the file name. The first fetch success skips the next locations. Notice that for file:// Avocado creates a symbolic link in the cache directory, pointing to the original location of the file.
  • expire: (optional) period while a cached file is considered valid. After that period, the file will be dowloaded again. The value can be an integer or a string containing the time and the unit. Example: ‘10d’ (ten days). Valid units are s (second), m (minute), h (hour) and d (day).
  • find_only: (optional) tries to find the asset in the cache. If the asset file is not available in the cache, Avocado will not attempt to download it.
  • cancel_on_missing (optional) if set to True, cancel the current running test if there is a problem while downloading the asset or if find_only=True and the asset is not available in the cache.

The expected return of the method is the asset file path or an exception.

Test Output Check and Output Record Mode

In a lot of occasions, you want to go simpler: just check if the output of a given test matches an expected output. In order to help with this common use case, Avocado provides the --output-check-record option:

--output-check-record {none,stdout,stderr,both,combined,all}
                      Record the output produced by each test (from stdout
                      and stderr) into both the current executing result and
                      into reference files. Reference files are used on
                      subsequent runs to determine if the test produced the
                      expected output or not, and the current executing
                      result is used to check against a previously recorded
                      reference file. Valid values: 'none' (to explicitly
                      disable all recording) 'stdout' (to record standard
                      output *only*), 'stderr' (to record standard error
                      *only*), 'both' (to record standard output and error
                      in separate files), 'combined' (for standard output
                      and error in a single file). 'all' is also a valid but
                      deprecated option that is a synonym of 'both'. This
                      option does not have a default value, but the Avocado
                      test runner will record the test under execution in
                      the most suitable way unless it's explicitly disabled
                      with value 'none'

If this option is used, Avocado will store the content generated by the test in the standard (POSIX) streams, that is, STDOUT and STDERR. Depending on the option chosen, you may end up with different files recorded (into what we call “reference files”):

  • stdout will produce a file named stdout.expected with the contents from the test process standard output stream (file descriptor 1)
  • stderr will produce a file named stderr.expected with the contents from the test process standard error stream (file descriptor 2)
  • both will produce both a file named stdout.expected and a file named stderr.expected
  • combined: will produce a single file named output.expected, with the content from both test process standard output and error streams (file descriptors 1 and 2)
  • none will explicitly disable all recording of test generated output and the generation reference files with that content

The reference files will be recorded in the first (most specific) test’s data dir (Accessing test data files). Let’s take as an example the test synctest.py. In a fresh checkout of the Avocado source code you can find the following reference files:

examples/tests/synctest.py.data/stderr.expected
examples/tests/synctest.py.data/stdout.expected

From those 2 files, only stdout.expected has some content:

$ cat examples/tests/synctest.py.data/stdout.expected
PAR : waiting
PASS : sync interrupted

This means that during a previous test execution, output was recorded with option --output-check-record both and content was generated on the STDOUT stream only:

$ avocado run --output-check-record both synctest.py
JOB ID     : b6306504351b037fa304885c0baa923710f34f4a
JOB LOG    : $JOB_RESULTS_DIR/job-2017-11-26T16.42-b630650/job.log
 (1/1) examples/tests/synctest.py:SyncTest.test: PASS (2.03 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 0
JOB TIME   : 2.26 s

After the reference files are added, the check process is transparent, in the sense that you do not need to provide special flags to the test runner. From this point on, after such as test (one with a reference file recorded) has finished running, Avocado will check if the output generated match the reference(s) file(s) content. If they don’t match, the test will finish with a FAIL status.

You can disable this automatic check when a reference file exists by passing --output-check=off to the test runner.

Tip

The avocado.utils.process APIs have a parameter called allow_output_check that let you individually select the output that will be part of the test output and recorded reference files. Some other APIs built on top of avocado.utils.process, such as the ones in avocado.utils.build also provide the same parameter.

This process works fine also with simple tests, which are programs or shell scripts that returns 0 (PASSed) or != 0 (FAILed). Let’s consider our bogus example:

$ cat output_record.sh
#!/bin/bash
echo "Hello, world!"

Let’s record the output for this one:

$ avocado run output_record.sh --output-check-record all
JOB ID    : 25c4244dda71d0570b7f849319cd71fe1722be8b
JOB LOG   : $HOME/avocado/job-results/job-2014-09-25T20.49-25c4244/job.log
 (1/1) output_record.sh: PASS (0.01 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0
JOB TIME   : 0.11 s

After this is done, you’ll notice that a the test data directory appeared in the same level of our shell script, containing 2 files:

$ ls output_record.sh.data/
stderr.expected  stdout.expected

Let’s look what’s in each of them:

$ cat output_record.sh.data/stdout.expected
Hello, world!
$ cat output_record.sh.data/stderr.expected
$

Now, every time this test runs, it’ll take into account the expected files that were recorded, no need to do anything else but run the test. Let’s see what happens if we change the stdout.expected file contents to Hello, Avocado!:

$ avocado run output_record.sh
JOB ID    : f0521e524face93019d7cb99c5765aedd933cb2e
JOB LOG   : $HOME/avocado/job-results/job-2014-09-25T20.52-f0521e5/job.log
 (1/1) output_record.sh: FAIL (0.02 s)
RESULTS    : PASS 0 | ERROR 0 | FAIL 1 | SKIP 0 | WARN 0 | INTERRUPT 0
JOB TIME   : 0.12 s

Verifying the failure reason:

$ cat $HOME/avocado/job-results/latest/job.log
    2017-10-16 14:23:02,567 test             L0381 INFO | START 1-output_record.sh
    2017-10-16 14:23:02,568 test             L0402 DEBUG| Test metadata:
    2017-10-16 14:23:02,568 test             L0403 DEBUG|   filename: $HOME/output_record.sh
    2017-10-16 14:23:02,596 process          L0389 INFO | Running '$HOME/output_record.sh'
    2017-10-16 14:23:02,603 process          L0499 INFO | Command '$HOME/output_record.sh' finished with 0 after 0.00131011009216s
    2017-10-16 14:23:02,602 process          L0479 DEBUG| [stdout] Hello, world!
    2017-10-16 14:23:02,603 test             L1084 INFO | Exit status: 0
    2017-10-16 14:23:02,604 test             L1085 INFO | Duration: 0.00131011009216
    2017-10-16 14:23:02,604 test             L0274 DEBUG| DATA (filename=stdout.expected) => $HOME/output_record.sh.data/stdout.expected (found at file source dir)
    2017-10-16 14:23:02,605 test             L0740 DEBUG| Stdout Diff:
    2017-10-16 14:23:02,605 test             L0742 DEBUG| --- $HOME/output_record.sh.data/stdout.expected
    2017-10-16 14:23:02,605 test             L0742 DEBUG| +++ $HOME/avocado/job-results/job-2017-10-16T14.23-8cba866/test-results/1-output_record.sh/stdout
    2017-10-16 14:23:02,605 test             L0742 DEBUG| @@ -1 +1 @@
    2017-10-16 14:23:02,605 test             L0742 DEBUG| -Hello, Avocado!
    2017-10-16 14:23:02,605 test             L0742 DEBUG| +Hello, world!
    2017-10-16 14:23:02,606 stacktrace       L0041 ERROR|
    2017-10-16 14:23:02,606 stacktrace       L0044 ERROR| Reproduced traceback from: $HOME/git/avocado/avocado/core/test.py:872
    2017-10-16 14:23:02,606 stacktrace       L0047 ERROR| Traceback (most recent call last):
    2017-10-16 14:23:02,606 stacktrace       L0047 ERROR|   File "$HOME/git/avocado/avocado/core/test.py", line 743, in _check_reference_stdout
    2017-10-16 14:23:02,606 stacktrace       L0047 ERROR|     self.fail('Actual test sdtout differs from expected one')
    2017-10-16 14:23:02,606 stacktrace       L0047 ERROR|   File "$HOME//git/avocado/avocado/core/test.py", line 983, in fail
    2017-10-16 14:23:02,607 stacktrace       L0047 ERROR|     raise exceptions.TestFail(message)
    2017-10-16 14:23:02,607 stacktrace       L0047 ERROR| TestFail: Actual test sdtout differs from expected one
    2017-10-16 14:23:02,607 stacktrace       L0048 ERROR|
    2017-10-16 14:23:02,607 test             L0274 DEBUG| DATA (filename=stderr.expected) => $HOME//output_record.sh.data/stderr.expected (found at file source dir)
    2017-10-16 14:23:02,608 test             L0965 ERROR| FAIL 1-output_record.sh -> TestFail: Actual test sdtout differs from expected one

As expected, the test failed because we changed its expectations, so an unified diff was logged. The unified diffs are also present in the files stdout.diff and stderr.diff, present in the test results directory:

$ cat $HOME/avocado/job-results/latest/test-results/1-output_record.sh/stdout.diff
--- $HOME/output_record.sh.data/stdout.expected
+++ $HOME/avocado/job-results/job-2017-10-16T14.23-8cba866/test-results/1-output_record.sh/stdout
@@ -1 +1 @@
-Hello, Avocado!
+Hello, world!

Note

Currently the stdout, stderr and output files are stored in text mode. Data that can not be decoded according to current locale settings, will be replaced according to https://docs.python.org/3/library/codecs.html#codecs.replace_errors.

Test log, stdout and stderr in native Avocado modules

If needed, you can write directly to the expected stdout and stderr files from the native test scope. It is important to make the distinction between the following entities:

  • The test logs
  • The test expected stdout
  • The test expected stderr

The first one is used for debugging and informational purposes. Additionally writing to self.log.warning causes test to be marked as dirty and when everything else goes well the test ends with WARN. This means that the test passed but there were non-related unexpected situations described in warning log.

You may log something into the test logs using the methods in avocado.Test.log class attributes. Consider the example:

class output_test(Test):

    def test(self):
        self.log.info('This goes to the log and it is only informational')
        self.log.warn('Oh, something unexpected, non-critical happened, '
                      'but we can continue.')
        self.log.error('Describe the error here and don't forget to raise '
                       'an exception yourself. Writing to self.log.error '
                       'won't do that for you.')
        self.log.debug('Everybody look, I had a good lunch today...')

If you need to write directly to the test stdout and stderr streams, Avocado makes two preconfigured loggers available for that purpose, named avocado.test.stdout and avocado.test.stderr. You can use Python’s standard logging API to write to them. Example:

import logging

class output_test(Test):

    def test(self):
        stdout = logging.getLogger('avocado.test.stdout')
        stdout.info('Informational line that will go to stdout')
        ...
        stderr = logging.getLogger('avocado.test.stderr')
        stderr.info('Informational line that will go to stderr')

Avocado will automatically save anything a test generates on STDOUT into a stdout file, to be found at the test results directory. The same applies to anything a test generates on STDERR, that is, it will be saved into a stderr file at the same location.

Additionally, when using the runner’s output recording features, namely the --output-check-record argument with values stdout, stderr or all, everything given to those loggers will be saved to the files stdout.expected and stderr.expected at the test’s data directory (which is different from the job/test results directory).

Setting a Test Timeout

Sometimes your test suite/test might get stuck forever, and this might impact your test grid. You can account for that possibility and set up a timeout parameter for your test. The test timeout can be set through the test parameters, as shown below.

sleep_length: 5
timeout: 3
$ avocado run sleeptest.py --mux-yaml /tmp/sleeptest-example.yaml
JOB ID     : c78464bde9072a0b5601157989a99f0ba32a288e
JOB LOG    : $HOME/avocado/job-results/job-2016-11-02T11.13-c78464b/job.log
 (1/1) sleeptest.py:SleepTest.test: INTERRUPTED (3.04 s)
RESULTS    : PASS 0 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 1
JOB TIME   : 3.14 s
JOB HTML   : $HOME/avocado/job-results/job-2016-11-02T11.13-c78464b/html/results.html
$ cat $HOME/avocado/job-results/job-2016-11-02T11.13-c78464b/job.log
2016-11-02 11:13:01,133 job              L0384 INFO | Multiplex tree representation:
2016-11-02 11:13:01,133 job              L0386 INFO |  \-- run
2016-11-02 11:13:01,133 job              L0386 INFO |         -> sleep_length: 5
2016-11-02 11:13:01,133 job              L0386 INFO |         -> timeout: 3
2016-11-02 11:13:01,133 job              L0387 INFO |
2016-11-02 11:13:01,134 job              L0391 INFO | Temporary dir: /var/tmp/avocado_PqDEyC
2016-11-02 11:13:01,134 job              L0392 INFO |
2016-11-02 11:13:01,134 job              L0399 INFO | Variant 1:    /run
2016-11-02 11:13:01,134 job              L0402 INFO |
2016-11-02 11:13:01,134 job              L0311 INFO | Job ID: c78464bde9072a0b5601157989a99f0ba32a288e
2016-11-02 11:13:01,134 job              L0314 INFO |
2016-11-02 11:13:01,345 sysinfo          L0107 DEBUG| Not logging /proc/pci (file does not exist)
2016-11-02 11:13:01,351 sysinfo          L0105 DEBUG| Not logging /proc/slabinfo (lack of permissions)
2016-11-02 11:13:01,355 sysinfo          L0107 DEBUG| Not logging /sys/kernel/debug/sched_features (file does not exist)
2016-11-02 11:13:01,388 sysinfo          L0388 INFO | Commands configured by file: /etc/avocado/sysinfo/commands
2016-11-02 11:13:01,388 sysinfo          L0399 INFO | Files configured by file: /etc/avocado/sysinfo/files
2016-11-02 11:13:01,388 sysinfo          L0419 INFO | Profilers configured by file: /etc/avocado/sysinfo/profilers
2016-11-02 11:13:01,388 sysinfo          L0427 INFO | Profiler disabled
2016-11-02 11:13:01,394 multiplexer      L0166 DEBUG| PARAMS (key=timeout, path=*, default=None) => 3
2016-11-02 11:13:01,395 test             L0216 INFO | START 1-sleeptest.py:SleepTest.test
2016-11-02 11:13:01,396 multiplexer      L0166 DEBUG| PARAMS (key=sleep_length, path=*, default=1) => 5
2016-11-02 11:13:01,396 sleeptest        L0022 DEBUG| Sleeping for 5.00 seconds
2016-11-02 11:13:04,411 stacktrace       L0038 ERROR|
2016-11-02 11:13:04,412 stacktrace       L0041 ERROR| Reproduced traceback from: $HOME/src/avocado/avocado/core/test.py:454
2016-11-02 11:13:04,412 stacktrace       L0044 ERROR| Traceback (most recent call last):
2016-11-02 11:13:04,413 stacktrace       L0044 ERROR|   File "/usr/share/doc/avocado/tests/sleeptest.py", line 23, in test
2016-11-02 11:13:04,413 stacktrace       L0044 ERROR|     time.sleep(sleep_length)
2016-11-02 11:13:04,413 stacktrace       L0044 ERROR|   File "$HOME/src/avocado/avocado/core/runner.py", line 293, in sigterm_handler
2016-11-02 11:13:04,413 stacktrace       L0044 ERROR|     raise SystemExit("Test interrupted by SIGTERM")
2016-11-02 11:13:04,414 stacktrace       L0044 ERROR| SystemExit: Test interrupted by SIGTERM
2016-11-02 11:13:04,414 stacktrace       L0045 ERROR|
2016-11-02 11:13:04,414 test             L0459 DEBUG| Local variables:
2016-11-02 11:13:04,440 test             L0462 DEBUG|  -> self <class 'sleeptest.SleepTest'>: 1-sleeptest.py:SleepTest.test
2016-11-02 11:13:04,440 test             L0462 DEBUG|  -> sleep_length <type 'int'>: 5
2016-11-02 11:13:04,440 test             L0592 ERROR| ERROR 1-sleeptest.py:SleepTest.test -> TestError: SystemExit('Test interrupted by SIGTERM',): Test interrupted by SIGTERM

The YAML file defines a test parameter timeout which overrides the default test timeout before the runner ends the test forcefully by sending a class:signal.SIGTERM to the test, making it raise a avocado.core.exceptions.TestTimeoutError.

Skipping Tests

To skip tests is in Avocado, you must use one of the Avocado skip decorators:

  • @avocado.skip(reason): Skips a test.
  • @avocado.skipIf(condition, reason): Skips a test if the condition is True.
  • @avocado.skipUnless(condition, reason): Skips a test if the condition is False

Those decorators can be used with both setUp() method and/or and in the test*() methods. The test below:

import avocado

class MyTest(avocado.Test):

    @avocado.skipIf(1 == 1, 'Skipping on True condition.')
    def test1(self):
        pass

    @avocado.skip("Don't want this test now.")
    def test2(self):
        pass

    @avocado.skipUnless(1 == 1, 'Skipping on False condition.')
    def test3(self):
        pass

Will produce the following result:

$ avocado run  test_skip_decorators.py
JOB ID     : 59c815f6a42269daeaf1e5b93e52269fb8a78119
JOB LOG    : $HOME/avocado/job-results/job-2017-02-03T17.41-59c815f/job.log
 (1/3) test_skip_decorators.py:MyTest.test1: SKIP
 (2/3) test_skip_decorators.py:MyTest.test2: SKIP
 (3/3) test_skip_decorators.py:MyTest.test3: PASS (0.02 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 2 | WARN 0 | INTERRUPT 0
JOB TIME   : 0.13 s
JOB HTML   : $HOME/avocado/job-results/job-2017-02-03T17.41-59c815f/html/results.html

Notice the test3 was not skipped because the provided condition was not False.

Using the skip decorators, nothing is actually executed. We will skip the setUp() method, the test method and the tearDown() method.

Note

It’s an erroneous condition, reported with test status ERROR, to use any of the skip decorators on the tearDown() method.

Cancelling Tests

You can cancel a test calling self.cancel() at any phase of the test (setUp(), test method or tearDown()). Test will finish with CANCEL status and will not make the Job to exit with a non-0 status. Example:

from avocado import Test

from avocado.utils.process import run
from avocado.utils.software_manager import SoftwareManager


class CancelTest(Test):

    """
    Example tests that cancel the current test from inside the test.
    """

    def setUp(self):
        sm = SoftwareManager()
        self.pkgs = sm.list_all(software_components=False)

    def test_iperf(self):
        if 'iperf-2.0.8-6.fc25.x86_64' not in self.pkgs:
            self.cancel('iperf is not installed or wrong version')
        self.assertIn('pthreads',
                      run('iperf -v', ignore_status=True).stderr)

    def test_gcc(self):
        if 'gcc-6.3.1-1.fc25.x86_64' not in self.pkgs:
            self.cancel('gcc is not installed or wrong version')
        self.assertIn('enable-gnu-indirect-function',
                      run('gcc -v', ignore_status=True).stderr)

In a system missing the iperf package but with gcc installed in the correct version, the result will be:

JOB ID     : 39c1f120830b9769b42f5f70b6b7bad0b1b1f09f
JOB LOG    : $HOME/avocado/job-results/job-2017-03-10T16.22-39c1f12/job.log
 (1/2) /home/apahim/avocado/tests/test_cancel.py:CancelTest.test_iperf: CANCEL (1.15 s)
 (2/2) /home/apahim/avocado/tests/test_cancel.py:CancelTest.test_gcc: PASS (1.13 s)
RESULTS    : PASS 1 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 | CANCEL 1
JOB TIME   : 2.38 s
JOB HTML   : $HOME/avocado/job-results/job-2017-03-10T16.22-39c1f12/html/results.html

Notice that using the self.cancel() will cancel the rest of the test from that point on, but the tearDown() will still be executed.

Depending on the result format you’re referring to, the CANCEL status is mapped to a corresponding valid status in that format. See the table below:

Format Corresponding Status
json cancel
xunit skipped
tap ok
html CANCEL (warning)

Docstring Directives

Some Avocado features, usually only available to instrumented tests, depend on setting directives on the test’s class docstring. A docstring directive is composed of a marker (a literal :avocado: string), followed by the custom content itself, such as :avocado: directive.

This is similar to docstring directives such as :param my_param: description and shouldn’t be a surprise to most Python developers.

The reason Avocado uses those docstring directives (instead of real Python code) is that the inspection done while looking for tests does not involve any execution of code.

For a detailed explanation about what makes a docstring format valid or not, please refer to our section on Docstring Directives Rules.

Now let’s follow with some docstring directives examples.

Declaring test as NOT-INSTRUMENTED

In order to say this class is not an Avocado instrumented test, one can use :avocado: disable directive. The result is that this class itself is not discovered as an instrumented test, but children classes might inherit it’s test* methods (useful for base-classes):

from avocado import Test

class BaseClass(Test):
    """
    :avocado: disable
    """
    def test_shared(self):
        pass

class SpecificTests(BaseClass):
    def test_specific(self):
        pass

Results in:

INSTRUMENTED test.py:SpecificTests.test_specific
INSTRUMENTED test.py:SpecificTests.test_shared

The test.py:BaseBase.test is not discovered due the tag while the test.py:SpecificTests.test_shared is inherited from the base-class.

Declaring test as INSTRUMENTED

The :avocado: enable tag might be useful when you want to override that this is an INSTRUMENTED test, even though it is not inherited from avocado.Test class and/or when you want to only limit the test* methods discovery to the current class:

from avocado import Test

class NotInheritedFromTest:
    """
    :avocado: enable
    """
    def test(self):
        pass

class BaseClass(Test):
    """
    :avocado: disable
    """
    def test_shared(self):
        pass

class SpecificTests(BaseClass):
    """
    :avocado: enable
    """
    def test_specific(self):
        pass

Results in:

INSTRUMENTED test.py:NotInheritedFromTest.test
INSTRUMENTED test.py:SpecificTests.test_specific

The test.py:NotInheritedFromTest.test will not really work as it lacks several required methods, but still is discovered as an INSTRUMENTED test due to enable tag and the SpecificTests only looks at it’s test* methods, ignoring the inheritance, therefor the test.py:SpecificTests.test_shared will not be discovered.

(Deprecated) enabling recursive discovery

The :avocado: recursive tag was used to enable recursive discovery, but nowadays this is the default. By using this tag one explicitly sets the class as INSTRUMENTED, therefor inheritance from avocado.Test is not required.

Categorizing tests

Avocado allows tests to be given tags, which can be used to create test categories. With tags set, users can select a subset of the tests found by the test resolver (also known as test loader).

To make this feature easier to grasp, let’s work with an example: a single Python source code file, named perf.py, that contains both disk and network performance tests:

from avocado import Test

class Disk(Test):

    """
    Disk performance tests

    :avocado: tags=disk,slow,superuser,unsafe
    """

    def test_device(self):
        device = self.params.get('device', default='/dev/vdb')
        self.whiteboard = measure_write_to_disk(device)


class Network(Test):

    """
    Network performance tests

    :avocado: tags=net,fast,safe
    """

    def test_latency(self):
        self.whiteboard = measure_latency()

    def test_throughput(self):
        self.whiteboard = measure_throughput()


class Idle(Test):

    """
    Idle tests
    """

    def test_idle(self):
        self.whiteboard = "test achieved nothing"

Warning

All docstring directives in Avocado require a strict format, that is, :avocado: followed by one or more spaces, and then followed by a single value with no white spaces in between. This means that an attempt to write a docstring directive like :avocado: tags=foo, bar will be interpreted as :avocado: tags=foo,.

Test tags can be applied to test classes and to test methods. Tags are evaluated per method, meaning that the class tags will be inherited by all methods, being merged with method local tags. Example:

from avocado import Test

class MyClass(Test):
    """
    :avocado: tags=furious
    """

    def test1(self):
        """
        :avocado: tags=fast
        """
        pass

    def test2(self):
        """
        :avocado: tags=slow
        """
        pass

If you use the tag furious, all tests will be included:

$ avocado list furious_tests.py --filter-by-tags=furious
INSTRUMENTED test_tags.py:MyClass.test1
INSTRUMENTED test_tags.py:MyClass.test2

But using fast and furious will include only test1:

$ avocado list furious_tests.py --filter-by-tags=fast,furious
INSTRUMENTED test_tags.py:MyClass.test1

Python unittest Compatibility Limitations And Caveats

When executing tests, Avocado uses different techniques than most other Python unittest runners. This brings some compatibility limitations that Avocado users should be aware.

Execution Model

One of the main differences is a consequence of the Avocado design decision that tests should be self contained and isolated from other tests. Additionally, the Avocado test runner runs each test in a separate process.

If you have a unittest class with many test methods and run them using most test runners, you’ll find that all test methods run under the same process. To check that behavior you could add to your setUp method:

def setUp(self):
    print("PID: %s", os.getpid())

If you run the same test under Avocado, you’ll find that each test is run on a separate process.

Class Level setUp and tearDown

Because of Avocado’s test execution model (each test is run on a separate process), it doesn’t make sense to support unittest’s unittest.TestCase.setUpClass() and unittest.TestCase.tearDownClass(). Test classes are freshly instantiated for each test, so it’s pointless to run code in those methods, since they’re supposed to keep class state between tests.

The setUp method is the only place in Avocado where you are allowed to call the skip method, given that, if a test started to be executed, by definition it can’t be skipped anymore. Avocado will do its best to enforce this boundary, so that if you use skip outside setUp, the test upon execution will be marked with the ERROR status, and the error message will instruct you to fix your test’s code.

If you require a common setup to a number of tests, the current recommended approach is to to write regular setUp and tearDown code that checks if a given state was already set. One example for such a test that requires a binary installed by a package:

from avocado import Test

from avocado.utils import software_manager
from avocado.utils import path as utils_path
from avocado.utils import process


class BinSleep(Test):

    """
    Sleeps using the /bin/sleep binary
    """
    def setUp(self):
        self.sleep = None
        try:
            self.sleep = utils_path.find_command('sleep')
        except utils_path.CmdNotFoundError:
            software_manager.install_distro_packages({'fedora': ['coreutils']})
            self.sleep = utils_path.find_command('sleep')

    def test(self):
        process.run("%s 1" % self.sleep)

If your test setup is some kind of action that will last accross processes, like the installation of a software package given in the previous example, you’re pretty much covered here.

If you need to keep other type of data a class across test executions, you’ll have to resort to saving and restoring the data from an outside source (say a “pickle” file). Finding and using a reliable and safe location for saving such data is currently not in the Avocado supported use cases.

Environment Variables for Tests

Avocado exports some information, including test parameters, as environment variables to the running test.

While these variables are available to all tests, they are usually more interesting to SIMPLE tests. The reason is that SIMPLE tests can not make direct use of Avocado API. INSTRUMENTED tests will usually have more powerful ways, to access the same information.

Here is a list of the variables that Avocado currently exports to tests:

Environemnt Variable Meaning Example
AVOCADO_VERSION Version of Avocado test runner 0.12.0
AVOCADO_TEST_BASEDIR Base directory of Avocado tests $HOME/Downloads/avocado-source/avocado
AVOCADO_TEST_WORKDIR Work directory for the test /var/tmp/avocado_Bjr_rd/my_test.sh
AVOCADO_TESTS_COMMON_TMPDIR Temporary directory created by the teststmpdir plugin. The directory is persistent throughout the tests in the same Job /var/tmp/avocado_XhEdo/
AVOCADO_TEST_LOGDIR Log directory for the test $HOME/logs/job-results/job-2014-09-16T14.38-ac332e6/test-results/$HOME/my_test.sh.1
AVOCADO_TEST_LOGFILE Log file for the test $HOME/logs/job-results/job-2014-09-16T14.38-ac332e6/test-results/$HOME/my_test.sh.1/debug.log
AVOCADO_TEST_OUTPUTDIR Output directory for the test $HOME/logs/job-results/job-2014-09-16T14.38-ac332e6/test-results/$HOME/my_test.sh.1/data
AVOCADO_TEST_SYSINFODIR The system information directory $HOME/logs/job-results/job-2014-09-16T14.38-ac332e6/test-results/$HOME/my_test.sh.1/sysinfo
*** All variables from –mux-yaml TIMEOUT=60; IO_WORKERS=10; VM_BYTES=512M; …

Warning

AVOCADO_TEST_SRCDIR was present in earlier versions, but has been deprecated on version 60.0, and removed on version 62.0. Please use AVOCADO_TEST_WORKDIR instead.

Warning

AVOCADO_TEST_DATADIR was present in earlier versions, but has been deprecated on version 60.0, and removed on version 62.0. The test data files (and directories) are now dynamically evaluated and are not available as environment variables

SIMPLE Tests BASH extensions

SIMPLE tests written in shell can use a few Avocado utilities. In your shell code, check if the libraries are available with something like:

AVOCADO_SHELL_EXTENSIONS_DIR=$(avocado exec-path 2>/dev/null)

And if available, injects that directory containing those utilities into the PATH used by the shell, making those utilities readily accessible:

if [ $? == 0 ]; then
  PATH=$AVOCADO_SHELL_EXTENSIONS_DIR:$PATH
fi

For a full list of utilities, take a look into at the directory return by avocado exec-path (if any). Also, the example test examples/tests/simplewarning.sh can serve as further inspiration.

Tip

These extensions may be available as a separate package. For RPM packages, look for the bash sub-package.

SIMPLE Tests Status

With SIMPLE tests, Avocado checks the exit code of the test to determine whether the test PASSed or FAILed.

If your test exits with exit code 0 but you still want to set a different test status in some conditions, Avocado can search a given regular expression in the test outputs and, based on that, set the status to WARN or SKIP.

To use that feature, you have to set the proper keys in the configuration file. For instance, to set the test status to SKIP when the test outputs a line like this: ‘11:08:24 Test Skipped’:

[simpletests.output]
skip_regex = ^\d\d:\d\d:\d\d Test Skipped$

That configuration will make Avocado to search the Python Regular Expression on both stdout and stderr. If you want to limit the search for only one of them, there’s another key for that configuration, resulting in:

[simpletests.output]
skip_regex = ^\d\d:\d\d:\d\d Test Skipped$
skip_location = stderr

The equivalent settings can be present for the WARN status. For instance, if you want to set the test status to WARN when the test outputs a line starting with string WARNING:, the configuration file will look like this:

[simpletests.output]
skip_regex = ^\d\d:\d\d:\d\d Test Skipped$
skip_location = stderr
warn_regex = ^WARNING:
warn_location = all

Job Cleanup

It’s possible to register a callback function that will be called when all the tests have finished running. This effectively allows for a test job to clean some state it may have left behind.

At the moment, this feature is not intended to be used by test writers, but it’s seen as a feature for Avocado extensions to make use.

To register a callback function, your code should put a message in a very specific format in the “runner queue”. The Avocado test runner code will understand that this message contains a (serialized) function that will be called once all tests finish running.

Example:

from avocado import Test

def my_cleanup(path_to_file):
   if os.path.exists(path_to_file):
      os.unlink(path_to_file)

class MyCustomTest(Test):
...
   cleanup_file = '/tmp/my-custom-state'
   self.runner_queue.put({"func_at_exit": self.my_cleanup,
                          "args": (cleanup_file),
                          "once": True})
...

This results in the my_cleanup function being called with positional argument cleanup_file.

Because once was set to True, only one unique combination of function, positional arguments and keyword arguments will be registered, not matter how many times they’re attempted to be registered. For more information check avocado.utils.data_structures.CallbackRegister.register().

Docstring Directives Rules

Avocado INSTRUMENTED tests, those written in Python and using the avocado.Test API, can make use of special directives specified as docstrings.

To be considered valid, the docstring must match this pattern: avocado.core.safeloader.DOCSTRING_DIRECTIVE_RE_RAW.

An Avocado docstring directive has two parts:

  1. The marker, which is the literal string :avocado:.
  2. The content, a string that follows the marker, separated by at least one white space or tab.

The following is a list of rules that makes a docstring directive be a valid one:

  • It should start with :avocado:, which is the docstring directive “marker”
  • At least one whitespace or tab must follow the marker and preceed the docstring directive “content”
  • The “content”, which follows the marker and the space, must begin with an alphanumeric character, that is, characters within “a-z”, “A-Z” or “0-9”.
  • After at least one alphanumeric character, the content may contain the following special symbols too: _, ,, = and :.
  • An end of string (or end of line) must immediately follow the content.

Signal Handlers

Avocado normal operation is related to run code written by users/test-writers. It means the test code can carry its own handlers for different signals or even ignore then. Still, as the code is being executed by Avocado, we have to make sure we will finish all the subprocesses we create before ending our execution.

Signals sent to the Avocado main process will be handled as follows:

  • SIGSTP/Ctrl+Z: On SIGSTP, Avocado will pause the execution of the subprocesses, while the main process will still be running, respecting the timeout timer and waiting for the subprocesses to finish. A new SIGSTP will make the subprocesses to resume the execution.
  • SIGINT/Ctrl+C: This signal will be forwarded to the test process and Avocado will wait until it’s finished. If the test process does not finish after receiving a SIGINT, user can send a second SIGINT (after the 2 seconds ignore period). The second SIGINT will make Avocado to send a SIGKILL to the whole subprocess tree and then complete the main process execution.
  • SIGTERM: This signal will make Avocado to terminate immediately. A SIGKILL will be sent to the whole subprocess tree and the main process will exit without completing the execution. Notice that it’s a best-effort attempt, meaning that in case of fork-bomb, newly created processes might still be left behind.

Wrap Up

We recommend you take a look at the example tests present in the examples/tests directory, that contains a few samples to take some inspiration from. That directory, besides containing examples, is also used by the Avocado self test suite to do functional testing of Avocado itself. Although one can inspire in https://github.com/avocado-framework-tests where people are allowed to share their basic system tests.

It is also recommended that you take a look at the Test APIs. for more possibilities.

[1]sleeptest is a functional test for Avocado. It’s “old” because we also have had such a test for Autotest for a long time.