stestr user manual¶
Usage¶
Overview¶
stestr is an application for running and tracking test results. Any test run that can be represented as a subunit stream can be inserted into a repository. However, the test running mechanism assumes python is being used. It is originally forked from the testrepository project so the usage is similar.
A typical basic example workflow is:
# Create a store to manage test results in.
$ stestr init
# Do a test run
$ stestr run
Most commands in testr have comprehensive online help, and the commands:
$ stestr --help
$ stestr [command] --help
Will be useful to explore the system.
Configuration¶
To configure stestr for a project you can write a stestr configuration file.
This lets you set basic information about how tests are run for a project.
By default the config file needs to be .stestr.conf in the same directory
that stestr is run from, normally the root of a project’s repository. However,
the --config/-c CLI argument can specify an alternate path for it.
The 2 most important options in the stestr config file are test_path
and top_dir. These 2 options are used to set the unittest discovery
options for stestr. (test_path is the same as --start-directory
and top_dir is the same as --top-level-directory in the doc) Only test_path
is a required field in the config file, if top_dir is not specified it defaults
to ./. It’s also worth noting that shell variables for these 2 config
options (and only these 2 options) are expanded on platforms that have a shell.
This enables you to have conditional discovery paths based on your environment.
For example, having a config file like:
[DEFAULT]
test_path=${TEST_PATH:-./foo/tests}
will let you override the discovery start path using the TEST_PATH environment variable.
A full example config file is:
[DEFAULT]
test_path=./project/tests
top_dir=./
group_regex=([^\.]*\.)*
The group_regex option is used to specify is used to provide a scheduler
hint for how tests should be divided between test runners. See the
Grouping Tests section for more information on how this works.
There is also an option to specify all the options in the config file via the
CLI. This way you can run stestr directly without having to write a config file
and manually specify the test_path like above with the --test-path/-t
CLI argument.
Running tests¶
To run tests the stestr run command is used. By default this will run all
tests discovered using the discovery parameters in the stestr config file.
If you’d like to avoid the overhead of test discovery and just manually execute
a single test (test class, or module) you can do this using the
--no-discover/-n option. For example:
$ stestr run --no-discover project.tests.test_foo.TestFoo
you can also give it a file path and stestr will convert that to the proper python path under the covers. (assuming your project don’t manually mess with import paths) For example:
$ stestr run --no-discover project/tests/test_foo.py
will also bypass discovery and directly call subunit.run on the module specified.
Test Selection¶
Arguments passed to stestr run are used to filter test ids that will be run.
stestr will perform unittest discovery to get a list of all test ids and then
apply each argument as a regex filter. Tests that match any of the given filters
will be run. For example, if you called stestr run foo bar this will only
run the tests that have a regex match with foo or a regex match with bar.
stestr allows you do to do simple test exclusion via passing a rejection/black regexp:
$ stestr run --black-regex 'slow_tests|bad_tests'
stestr also allow you to combine these arguments:
$ stestr run --black-regex 'slow_tests|bad_tests' ui\.interface
Here first we selected all tests which matches to ui\.interface, then we are
dropping all test which matches slow_tests|bad_tests from the final list.
stestr also allows you to specify a blacklist file to define a set of regexes
to exclude. You can specify a blacklist file with the
--blacklist-file/-b option, for example:
$ stestr run --blacklist-file $path_to_file
The format for the file is line separated regex, with # used to signify the
start of a comment on a line. For example:
# Blacklist File
^regex1 # Excludes these tests
.*regex2 # exclude those tests
The regexp used in the blacklist file or passed as argument, will be used to
drop tests from the initial selection list. It will generate a list which will
exclude any tests matching ^regex1 or .*regex2. If a blacklist file is
used in conjunction with the normal filters then the regex filters passed in as
an argument regex will be used for the initial test selection, and the
exclusion regexes from the blacklist file on top of that.
The dual of the blacklist file is the whitelist file which will include any
tests matching the regexes in the file. You can specify the path to the file
with --whitelist-file/-w, for example:
$ stestr run --whitelist-file $path_to_file
The format for the file is more or less identical to the blacklist file:
# Whitelist File
^regex1 # Include these tests
.*regex2 # include those tests
However, instead of excluding the matches it will include them.
It’s also worth noting that you can use the test list option to dry run any
selection arguments you are using. You just need to use stestr list
with your selection options to do this, for example:
$ stestr list 'regex3.*' --blacklist-file blacklist.txt
This will list all the tests which will be run by stestr using that combination of arguments.
Adjusting test run output¶
By default the stestr run command uses an output filter called
subunit-trace. (as does the stestr last command) This displays the tests
as they are finished executing, as well as their worker and status. It also
prints aggregate numbers about the run at the end. You can read more about
subunit-trace in the module doc: Subunit Trace.
However, the test run output is configurable, you can disable this output
with the --no-subunit-trace flag which will be completely silent except for
any failures it encounters. There is also the --color flag which will enable
colorization with subunit-trace output. If you prefer to deal with the raw
subunit yourself and run your own output rendering or filtering you can use
the --subunit flag to output the result stream as raw subunit v2.
There is also an --abbreviate flag available, when this is used a single
character is printed for each test as it is executed. A . is printed for a
successful test, a F for a failed test, and a S for a skipped test.
In the default subunit-trace output any captured output to stdout and stderr is
printed after test execution, for both successful and failed tests. However,
in some cases printing these attachments on a successful tests is not the
preferred behavior. You can use the --suppress-attachments flag to disable
printing stdout or stderr attachments for successful tests.
Combining Test Results¶
There is sometimes a use case for running a single test suite split between
multiple invocations of the stestr run command. For example, running a subset
of tests with a different concurrency. In these cases you can use the
--combine flag on stestr run. When this flag is specified stestr will
append the subunit stream from the test run into the most recent entry in the
repository.
Alternatively, you can manually load the test results from a subunit stream into
an existing test result in the repository using the --id/-i flag on
the stestr load command. This will append the results from the input subunit
stream to the specified id.
Running previously failed tests¶
stestr run also enables you to run just the tests that failed in the
previous run. To do this you can use the --failing argument.
A common workflow using this is:
# Run tests (and some fail)
$ stestr run
# Fix currently broken tests - repeat until there are no failures.
$ stestr run --failing
# Do a full run to find anything that regressed during the reduction process.
$ stestr run
The --failing option turns on --partial automatically (so that if the
partial test run were to be interrupted, the failing tests that aren’t run are
not lost).
Another common use case is repeating a failure that occurred on a remote machine (e.g. during a jenkins test run). There are a few common ways to do approach this.
Firstly, if you have a subunit stream from the run you can just load it:
$ stestr load < failing-stream
# Run the failed tests
$ stestr run --failing
The streams generated by test runs are in .stestr/ named for their test id - e.g. .stestr/0 is the first stream. Note for right now these files are stored in subunit v1, but all of stestr commands (including load) expect a subunit v2 stream.
If you have access to the remote machine you can also get the subunit stream by running:
$ stestr last --subunit > failing-stream
This is often a bit easier than trying to manually pull the stream file out of the .stestr directory. (also it will be in subunit v2)
If you do not have a stream or access to the machine you may be able to use a list file. If you can get a file that contains one test id per line, you can run the named tests like this:
$ stestr run --load-list FILENAME
This can also be useful when dealing with sporadically failing tests, or tests that only fail in combination with some other test - you can bisect the tests that were run to get smaller and smaller (or larger and larger) test subsets until the error is pinpointed.
stestr run --until-failure will run your test suite again and again and
again stopping only when interrupted or a failure occurs. This is useful
for repeating timing-related test failures.
Listing tests¶
To see a list of tests found by stestr you can use the stestr list command.
This will list all tests found by discovery.
You can also use this to see what tests will be run by a given stestr run
command. For instance, the tests that stestr run myfilter will run are shown
by stestr list myfilter. As with the run command, arguments to list are used
to regex filter the tests.
Parallel testing¶
stestr lets you run tests in parallel by default. So, it actually does this by def:
$ stestr run
This will first list the tests, partition the tests into one partition per CPU on the machine, and then invoke multiple test runners at the same time, with each test runner getting one partition. Currently the partitioning algorithm is simple round-robin for tests that stestr has not seen run before, and equal-time buckets for tests that stestr has seen run.
To determine how many CPUs are present in the machine, stestr will
use the multiprocessing Python module On operating systems where this is not
implemented, or if you need to control the number of workers that are used,
the --concurrency option will let you do so:
$ stestr run --concurrency=2
When running tests in parallel, stestr adds a tag for each test to the subunit
stream to show which worker executed that test. The tags are of the form
worker-%d and are usually used to reproduce test isolation failures, where
knowing exactly what test ran on a given worker is important. The %d that is
substituted in is the partition number of tests from the test run - all tests
in a single run with the same worker-N ran in the same test runner instance.
To find out which slave a failing test ran on just look at the ‘tags’ line in its test error:
======================================================================
label: testrepository.tests.ui.TestDemo.test_methodname
tags: foo worker-0
----------------------------------------------------------------------
error text
And then find tests with that tag:
$ stestr last --subunit | subunit-filter -s --xfail --with-tag=worker-3 | subunit-ls > slave-3.list
Grouping Tests¶
In certain scenarios you may want to group tests of a certain type together so
that they will be run by the same worker process. The group_regex option in
the stestr config file permits this. When set, tests are grouped by the entire
matching portion of the regex. The match must begin at the start of the string.
Tests with no match are not grouped.
For example, setting the following option in the stestr config file will group tests in the same class together (the last ‘.’ splits the class and test method):
group_regex=([^\.]+\.)+
Test Scheduling¶
By default stestr schedules the tests by first checking if there is any historical timing data on any tests. It then sorts the tests by that timing data loops over the tests in order and adds one to each worker that it will launch. For tests without timing data, the same is done, except the tests are in alphabetical order instead of based on timing data. If a group regex is used the same algorithm is used with groups instead of individual tests.
However there are options to adjust how stestr will schedule tests. The primary
option to do this is to manually schedule all the tests run. To do this use the
--worker-file option for stestr run. This takes a path to a yaml file that
instructs stestr how to run tests. It is formatted as a list of dicts with a
single element each with a list describing the tests to run on each worker. For
example:
- worker:
- regex 1
- worker:
- regex 2
- regex 3
would create 2 workers. The first would run all tests that match regex 1, and
the second would run all tests that match regex 2 or regex 3. In addition if
you need to mix manual scheduling and the standard scheduling mechanisms you
can accomplish this with the concurrency field on a worker in the yaml.
For example, building on the previous example:
- worker:
- regex 1
- worker:
- regex 2
- regex 3
- worker:
- regex 4
concurrency: 3
In this case the tests that match regex 4 will be run against 3 workers and the
tests will be partitioned across those workers with the normal scheduler. This
includes respecting the other scheduler options, like group_regex or
--random.
There is also an option on stestr run, --random/-r to randomize the
order of tests as they are passed to the workers. This is useful in certain
use cases, especially when you want to test isolation between test cases.
User Config Files¶
If you prefer to have a different default output or setting for a particular
command stestr enables you to write a user config file to overide the defaults
for some options on some commands. By default stestr will look for this config
file in ~/.stestr.yaml and ~/.config/stestr.yaml in that order. You
can also specify the path to a config file with the --user-config
parameter.
The config file is a yaml file that has a top level key for the command and then a sub key for each option. For an example, a fully populated config file that changes the default on all available options in the config file is:
run:
concurrency: 42 # This can be any integer value >= 0
random: True
no-subunit-trace: True
color: True
abbreviate: True
slowest: True
suppress-attachments: True
failing:
list: True
last:
no-subunit-trace: True
color: True
suppress-attachments: True
load:
force-init: True
subunit-trace: True
color: True
abbreviate: True
suppress-attachments: True
If you choose to use a user config file you can specify any subset of the options and commands you choose.
Automated test isolation bisection¶
As mentioned above, its possible to manually analyze test isolation issues by interrogating the repository for which tests ran on which worker, and then creating a list file with those tests, re-running only half of them, checking the error still happens, rinse and repeat.
However that is tedious. stestr can perform this analysis for you:
$ stestr run --analyze-isolation
will perform that analysis for you. The process is:
- The last run in the repository is used as a basis for analysing against - tests are only cross checked against tests run in the same worker in that run. This means that failures accrued from several different runs would not be processed with the right basis tests - you should do a full test run to seed your repository. This can be local, or just stestr load a full run from your Jenkins or other remote run environment.
- Each test that is currently listed as a failure is run in a test process given just that id to run.
- Tests that fail are excluded from analysis - they are broken on their own.
- The remaining failures are then individually analysed one by one.
- For each failing, it gets run in one work along with the first 1/2 of the tests that were previously run prior to it.
- If the test now passes, that set of prior tests are discarded, and the other half of the tests is promoted to be the full list. If the test fails then other other half of the tests are discarded and the current set promoted.
- Go back to running the failing test along with 1/2 of the current list of priors unless the list only has 1 test in it. If the failing test still failed with that test, we have found the isolation issue. If it did not then either the isolation issue is racy, or it is a 3-or-more test isolation issue. Neither of those cases are automated today.
Forcing isolation¶
Sometimes it is useful to force a separate test runner instance for each test
executed. The --isolated flag will cause stestr to execute a separate runner
per test:
$ stestr run --isolated
In this mode stestr first determines tests to run (either automatically listed,
using the failing set, or a user supplied load-list), and then spawns one test
runner per test it runs. To avoid cross-test-runner interactions concurrency
is disabled in this mode. --analyze-isolation supersedes --isolated if
they are both supplied.
Repositories¶
stestr uses a data repository to keep track of test previous test runs. There are different backend types that each offer different advantages. There are currently 2 repository types to choose from, file and sql.
You can choose which repository type you want with the --repo-type/-r
cli flag. file is the current default.
You can also specify an alternative repository with the --repo-url/-u
cli flags. The default value for a file repository type is to use the
directory: $CWD/.stestr. For a sql repository type is to use a sqlite
database located at: $CWD/.stestr.sqlite.
Note
Make sure you put these flags before the cli subcommand
Note
Different repository types that use local storage will conflict with each other in the same directory. If you initialize one repository type and then try to use another in the same directory, it will not work.
File¶
The default stestr repository type has a very simple disk structure. It contains the following files:
- format: This file identifies the precise layout of the repository, in case future changes are needed.
- next-stream: This file contains the serial number to be used when adding another stream to the repository.
- failing: This file is a stream containing just the known failing tests. It is updated whenever a new stream is added to the repository, so that it only references known failing tests.
- #N - all the streams inserted in the repository are given a serial number.
SQL¶
This is an experimental repository backend, that is based on the subunit2sql library. It’s currently still under development and should be considered experimental for the time being. Eventually it’ll replace the File repository type
Note
The sql repository type requirements are not installed by default.
They are listed under the ‘sql’ setuptools extras. You can install them
with pip by running: pip install 'stestr[sql]'