# stestr user manual

## Usage

A parallel Python test runner built around subunit

    stestr
        [--version]
        [-v | -q]
        [--log-file LOG_FILE]
        [--debug]
        [--user-config USER_CONFIG]
        [-d HERE]
        [--config CONFIG]
        [--repo-url REPO_URL]
        [--test-path TEST_PATH]
        [--top-dir TOP_DIR]
        [--group-regex GROUP_REGEX]
        [--parallel-class]

--version

  show program’s version number and exit

-v, --verbose

  Increase verbosity of output. Can be repeated.

-q, --quiet

  Suppress output except warnings and errors.

--log-file <LOG_FILE>

  Specify a file to log output. Disabled by default.

--debug

  Show tracebacks on errors.

--user-config <USER_CONFIG>

  An optional path to a default user config file if one is not specified ~/.stestr.yaml and ~/.config/stestr.yaml will be tried in that order

-d <HERE>, --here <HERE>

  Set the directory or url that a command should run from. This affects all default path lookups but does not affect paths supplied to the command.

--config <CONFIG>, -c <CONFIG>

  Set a stestr config file to use with this command. If one isn’t specified then .stestr.conf in the directory that a command is running from is used

--repo-url <REPO_URL>, -u <REPO_URL>

  Set the repo url to use. This should just be the path to the stestr repository directory

--test-path <TEST_PATH>, -t <TEST_PATH>

  Set the test path to use for unittest discovery. If both this and the corresponding config file option are set, this value will be used.

--top-dir <TOP_DIR>

  Set the top dir to use for unittest discovery. If both this and the corresponding config file option are set, this value will be used.

--group-regex <GROUP_REGEX>, --group_regex <GROUP_REGEX>, -g <GROUP_REGEX>

  Set a group regex to use for grouping tests together in the stestr scheduler. If both this and the corresponding config file option are set this value will be used.

--parallel-class, -p

  Set the flag to group tests by class. NOTE: This flag takes priority over the –group-regex option even if it’s set.

## 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. You can also specify the `parallel_class=True` instead of group_regex to group tests in the stestr scheduler together by class. Since this is a common use case this enables that without needing to memorize the complicated regex for `group_regex` to do this.

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.

### Tox

If you are also using tox with your project then it is not necessary to create separate stestr config file, instead you can embed the necessary configuration in the existing `tox.ini` file with an `[stestr]` section. For example a full configuration section would be:

    [stestr]
    test_path=./project/tests
    top_dir=./
    group_regex=([^\.]*\.)*

Any configuration directives outside the `[stestr]` section will be ignored. It’s important to note that if either the `--config`/`-c` CLI argument is specified, or the default location `.stestr.conf` file is present then any configuration in the `tox.ini` will be ignored. Configuration embedded in a `tox.ini` will only be used if other configuration files are not present.

### pyproject.toml

Similarly, if your project is using `pyproject.toml`, you may forego the config file, and instead create a `[tool.stestr]` section with the desired configuration options. For example:

    [tool.stestr]
    test_path = "./project/tests"
    top_dir = "./"
    group_regex = "([^\.]*\.)*"

The same caveats apply as the Tox with regards to CLI arguments.

### Configuration file precedence

The order in which configuration files are read is as follows:

- Any file specified with the `--config`/`-c` CLI argument

- The `.stestr.conf` file

- The `[tool.stestr]` section in a `pyproject.toml` file

- The `[stestr]` section in a `tox.ini` file

Also of note is that files specified with `--config-file`/`-c` may be either `.ini` or TOML format. If providing configs in `.ini` format, they must be in a `[DEFAULT]` section. If providing configs in TOML format, the configuration directives must be located in a `[tool.stestr]` section, and the filename must have a `.toml` extension.

## 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 the test runner on the module specified.

Additionally you can specify a specific class or method within that file using `::` to specify a class and method. For example:

    $ stestr run --no-discover project/tests/test_foo.py::TestFoo::test_method

will skip discovery and directly call the test runner on the test method in the specified test class.

### Running with pdb

If you’d like to run pdb during the execution of the tests you should use the `--pdb` flag on `stestr run`. This flag behaves the same way as the `--no-discover` flag except that it does not launch an external process to run the tests. This enables pdb to work as expected without any issues with the tradeoff that output from the test runner will occur after tests have finished execution.

It’s also worth noting that if you are using a fixture to capture stdout (which is a common practice for parallel test excecution) you’ll likely want to disable that fixture when running with pdb. Those fixtures can often interfere with pdb’s output and will sometimes capture output from pdb.

## 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 exclusion regexp:

    $ stestr run --exclude-regex 'slow_tests|bad_tests'

stestr also allow you to combine these arguments:

    $ stestr run --exclude-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 an exclusion list file to define a set of regexes to exclude. You can specify an exclusion list file with the `--exclude-list`/`-e` option, for example:

    $ stestr run --exclude-list $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:

    # Exclusion list File
    ^regex1 # Excludes these tests
    .*regex2 # exclude those tests

The regexp used in the exclusion list 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 an exclusion list 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 exclusion list file on top of that.

The dual of the exclusion list file is the inclusion list file which will include any tests matching the regexes in the file. You can specify the path to the file with `--include-list`/`-i`, for example:

    $ stestr run --include-list $path_to_file

The format for the file is more or less identical to the exclusion list file:

    # Inclusion list 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.*' --exclude-list exclusion_list.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.

While by default attachments for captured stdout and stderr are printed, it is also possible that a test has other text attachments (a common example is python logging) which are not printed on successful test execution, only on failures. If you would like to have these attachments also printed for successful tests you can use the `--all-attachments` flag to print all text attachments on both successful and failed tests. Both `--all-attachments` and `--suppress-attachments` can not be set at the same time. If both are set in the user config file then the `suppress-attachments` flag will take priority and no attachments will be printed for successful tests. If either `--suppress-attachments` or `--all-attachments` is set via the CLI it will take precedence over matching options set in the user config file.

## 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:

1. Run tests (and some fail):

       $ stestr run

2. Fix currently broken tests - repeat until there are no failures:

       $ stestr run --failing

3. Do a full run to find anything that regressed during the reduction process:

       $ stestr run

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

and then run the tests which failed from that loaded run:

    $ stestr run --failing

If using a file type repository (which is the default) the streams generated by test runs are in the repository path, which defaults to .stestr/ in the working directory, and stores the stream in a file named for their run id - e.g. .stestr/0 is the first run.

Note

For right now these files are stored in the subunit v1 format, but all of the stestr commands, including load, only work with the subunit v2 format. This can be converted using the subunit-1to2 tool in the python-subunit package.

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 the subunit v2 format already)

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=([^\.]+\.)+

However, because grouping tests at the class level is a common use case there is also a config option, `parallel_class`, to do this. For example, you can use:

    parallel_class=True

and it will group tests in the same class together.

Note

This `parallel_class` option takes priority over the `group_regex` option. And if both on the CLI and in the config are set, we use the option on the CLI not in a config file. For example, `--group-regex` on the CLI and `parallel-class` in a config file are set, `--group-regex` is higer priority than `parallel-class` in this case.

## 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` 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
      all-attachments: True
    failing:
      list: True
    last:
      no-subunit-trace: True
      color: True
      suppress-attachments: True
      all-attachments: True
    load:
      force-init: True
      subunit-trace: True
      color: True
      abbreviate: True
      suppress-attachments: True
      all-attachments: True
    history-list:
      show-metadata: True
    history-show:
      no-subunit-trace: True
      color: True
      suppress-attachments: True
      all-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:

1. 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.

2. Each test that is currently listed as a failure is run in a test process given just that id to run.

3. Tests that fail are excluded from analysis - they are broken on their own.

4. The remaining failures are then individually analysed one by one.

5. 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.

6. 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.

7. 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.

## History

stestr keeps a history of all test runs in a local repository. the `stestr history` command is used for interacting with those old runs. The history command has 3 sub-commands, `list`, `show`, and `remove`. The `list` sub-command will generate a list of the previous runs in the data repository and show some basic stats for each run. The `show` sub-command is used to retreive the record of a previous run, it behaves identically to `stestr last`, except that it takes an optional run id to show any run in the stestr history. If a run id is not specified it will use the most recent result. The `remove` sub-command will delete a specified run from the data repository. Additionally, the keyword `all` can be used to remove all runs from the repository. For example:

    $ stestr history remove all

## Repositories

stestr uses a data repository to keep track of test previous test runs.

You can also specify an alternative repository with the `--repo-url`/`-u` cli flags. The default value is to use the directory: `$CWD/.stestr`.

Note

Make sure you put these flags before the cli subcommand

The stestr repository 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.

- times.dbm: A dbm database (using Python’s ``dbm.dumb` <https://docs.python.org/3/library/dbm.html#module-dbm.dumb>`__ implementation) that stores the record of the last elapsed time for each test executed.

- meta.dbm: An dbm file that maps a run id (which will be the integer file documented above) to an arbitrary string metadata field describing the run. Right now this must be manually specified.