Python Execution and Testing Environment

The directory tests_python contains:

  • A scripting API to write execution scenarios involving several node, bakers, endorsers,
  • a system testing environment based on the pytest package.

Code organization

It contains the following python packages.

  • daemons defines classes to run Tezos node and daemons,
  • client mainly defines the Client class, that provides a programmatic interface to a client,
  • launcher defines classes used to launch a nodes and daemons with specific settings,
  • tools contains utility functions and constants shared by the tests,
  • examples contains example of tests and scripts that run scenarios of interactions between tezos nodes and clients,
  • tests contains pytest tests,
  • scripts contains utility scripts.

They are organized in three layers.

  1. daemons and client,
  2. launchers,
  3. tests, examples, tools.



  • A working environment (see documentation) with the binaries compiled,
  • python (version >= 3.6),
  • A local copy of the tezos repository
  • the pip package manager.

On some systems (e.g. Mac OS X), several versions of python coexist. You need to explicitly use python3 and pip3 (instead of python and pip).

Python packages can be installed with

cd PATH_TO_YOUR_TEZOS_DIR/tests_python
pip3 install -r requirements.txt

Examples of test executions:

pytest examples/  # simple test example
pytest -m "not slow"  # run all tests not marked as slow
pytest -s tests/  # run a specific test with traces
pytest  # run all tests

On systems where python packages are installed locally (e.g. test server at Nomadic), you need to export the local python binaries path.

export PATH=$PATH:~/.local/bin/

A simple sandbox scenario

The following example runs a couple of nodes and performs a transfer operation.

import time
from tools import constants, paths, utils
from launchers.sandbox import Sandbox

def scenario():
    """ a private tezos network, initialized with network parameters
        and some accounts. """
    with Sandbox(paths.TEZOS_HOME,
                constants.GENESIS_PK) as sandbox:
        # Launch node running protocol alpha
        # Launch a second node on the same private tezos network
        # Launch a baker associated to node 0, baking on behalf of delegate
        # bootstrap5
        sandbox.add_baker(0, 'bootstrap5', proto=constants.ALPHA_DEAMON)
        # first client tells node 0 to transfer money for an account to another
        # receipt is an object representing the client answer
        receipt = sandbox.client(0).transfer(500, 'bootstrap1', 'bootstrap3')
        transfer_hash = receipt.operation_hash
        # Wait for second node to update its protocol to alpha, if not
        # it may not know yet the ``wait_for_inclusion`` operation which is
        # protocol specific
        # second client waits for inclusion of operation by the second node

if __name__ == "__main__":

This can be run with python3 examples/ It should display all the clients commands and their results.

The sandbox object allows users to add nodes, bakers or endorsers running in tezos sandboxed mode. Whenever a node has been added, one can access it using a client object.

The client object is a wrapper on the tezos-client command. It runs tezos-client with “administrative” parameters, plus the parameters determined by the method called by the user.

For instance

receipt = client.transfer(500, 'bootstrap1', 'bootstrap3')

will run something like

tezos-client -base-dir /tmp/tezos-client.be22ya16 -addr -port 18730 transfer 500 from bootstrap1 to bootstrap3

receipt is an object of type client_ouput.TransferResult which gives access to some data of the tezos-client output.

Alternatively, one can always construct the command manually:

client_output =['transfer', '500', 'from', 'bootstrap1', 'bootstrap3'])

In that case, client_output is the string returned by the client, such as

Node is bootstrapped, ready for injecting operations.
Estimated gas: 10100 units (will add 100 for safety)
Estimated storage: no bytes added
Operation successfully injected in the node.
Operation hash is 'op9K2VJjKJLaFnfQKzsoz9rzr5v1PrLjpefiPtVhuiiXYgkZes1'

The first method is more convenient and less error prone. But the second method is more generic and sometimes the only option if the specialized method isn’t implemented.

Test suite and pytest

Tests are located in the tests directory and rely on the pytest library.

Tests are divided into modules, and are furthermore subdivided into classes. A class defines a full testing scenario. A typical scenario is a sequence of client commands and assertions, operating on a set of Tezos nodes running in a private network (a.k.a sandbox mode).

Running tests

Useful options

pytest has a variety of launching options. Conventient options include:

  • -v display test names,
  • -x stop at first failure,
  • -s display output, including commands launched and stdout from client (by default, pytest captures all passing test output and show failed tests output),
  • --tb=short, --tb=long, --tb=no, set size of python trace back in case of failure. Default is long and is too verbose in most case. The python trace back is useful to detect bugs in the python scripts,
  • --log-dir=<dir> saves all servers log in the given dir (CREATE <DIR> FIRST).
  • -x --pdb, start python debugger at first failure, this allows interacting with the node in the same context of the test,
  • -m TAGS_EXPR, run all tests containing some combination of tags.

-v and --tb=short are set by default in pytest initialization file.


Tests can be classified with tags. Tags are added with the annotation


The configuration file pytest.ini defines the list of allowed tags. It includes vote, multinode, baker, endorser, contract, slow, multibranch.


There are typically two ways of using pytest:

  • run a subset of the tests (batch mode),
  • or run a specific test.

In batch mode, we usually don’t care about traces. No particular option is needed, but sometimes we want to stop at first failure using -x, and some tests require the server logs to be saved (--log-dir=tmp/) as they check some assertions in the logs at some point in the test.

To run a specifc test, we usually want client and server traces (-s --log-dir=tmp/).

# Launch a simple test without capturing stdout
> pytest -s examples/
# run all tests about vote
> pytest -m "vote"
# run all vote and non-slow tests
> pytest -m "vote and not slow"
# run module, display all output, save server logs in tmp
> pytest -s tests/ --log-dir=tmp
# run all tests using a deamon
> pytest -m "endorser or baker"
# run everything
> pytest

Anatomy of a test

A typical testing scenario consists in:

  1. initializing the context (starting servers, setting up clients)
  2. running a sequence of commands and assertions
  3. releasing resources, terminating servers

This is done by grouping tests in a class, and managing the context in a fixture.

The following is the pytest counterpart of the first example.

import pytest
from tools import constants, paths, utils
from launchers.sandbox import Sandbox

def sandbox():
    """Example of sandbox fixture."""
    with Sandbox(paths.TEZOS_HOME,
                constants.GENESIS_PK) as sandbox:
        sandbox.add_baker(0, 'bootstrap5', proto=constants.ALPHA_DEAMON)
        yield sandbox
        assert sandbox.are_daemons_alive()

def session():
    """Example of dictionary fixture. Used for keeping data between tests."""
    yield {}

class TestExample:

    def test_wait_sync_proto(self, sandbox):
        clients = sandbox.all_clients()
        for client in clients:
            proto = "ProtoALphaALphaALphaALphaALphaALphaALphaALphaDdp3zK"
            assert utils.check_protocol(client, proto)

    def test_transfer(self, sandbox, session):
        receipt = sandbox.client(0).transfer(500, 'bootstrap1', 'bootstrap3')
        session['operation_hash'] = receipt.operation_hash

    def test_inclusion(self, sandbox, session):
        operation_hash = session['operation_hash']

In this example, we defined the fixtures in the same module, but they are generally shared between tests and put in

Currently, all tests scenarios in the test suite are defined as classes, consisting of a sequence of methods that are run incrementally (as specified with the annotation @pytest.mark.incremental). Classes are used to define the scope of a fixture, and a unit of incremental testing sequence. We don’t directly instanciate them, or use self.

Data between methods are shared using a dictionary session. For instance, we save the result of the transfer operation, and retrieve it in the next method.


The list of fixtures available is given by

pytest --fixtures

Most fixtures are defined in The most general fixture is sandbox. It allows to instanciate an arbitrary number of nodes and deamons. Other fixtures, such as client, are specialized versions (slightly more convenient than using sandbox directly). Fixtures can be defined directly in a module defining a test, or they can be shared.

Skipping tests

Sometimes, a test can’t be run. For instance, it is known to fail, or it relies on some resources that may not be available. In that case, the test can be skipped (instead of failing).

For instance, if no log dir has been specified, the test_check_logs tests are skipped using pytest.skip().

def test_check_logs(self, sandbox):
        if not sandbox.log_dir:

Alternatively, one can use the skip annotation:

@pytest.mark.skip(reason="Not yet implemented")

Adding a test

  • By imitation, choose an existing test that looks similar,
  • use the proper tags,
  • say briefly what the test is supposed to test in the class docstring,
  • Run the linters and typechecker make lint_all, and make typecheck in tests_python/, or simple make test-python-lint from the Tezos home directory. Note that linting and typechecking are enforced by the CI in the build stage.
  • If you modify the API (launchers or deamons), make sure you maintain the layers structure. API shouldn’t rely testing constants (tools/ or tools/

Testing on zeronet, alphanet,…

On master, protocol alpha is named ProtoALphaALphaALphaALphaALphaALphaALphaALphaDdp3zK, and deamons binary name are suffixed with alpha (tezos-baker-alpha, tezos-endorser-alpha…). However, on production branches, an actual hash of the protocol is used, and a shortened string is used to specify deamons.

For instance, on revision 816625bed0983f7201e4c369440a910f006beb1a of zeronet, protocol alpha is named PsddFKi32cMJ2qPjf43Qv5GDWLDPZb3T3bF6fLKiF5HtvHNU7aP and deamons are suffixed by 003-PsddFKi3 (tezos-baker-003-PsddFKi3).

To reduce coupling between tests and the actual branch to be tested, tests refer to protocol alpha using constants.ALPHA and constants.ALPHA_DEAMON rather than by hard-coded identifiers.

Tests based on fixed revisions (multibranch)

It is useful to test interactions between different server versions. There are currently two ways of doing this.

1. The Sandbox launcher can use binaries built from different revisions. Methods add_node, add_baker and add_endorser have an optional parameter branch that points to a subdirectory where binaries are to be looked for.

2. The SandboxMultibranch launcher is instanciated by map from ids to branches. Then everytime we launch a node or a deamon the actual binary will be selected according to the map.

Tests using specific revisions are in tests/multibranch and aren’t run by default. They are not regression tests and are usually launched separately from the rest of the tests. To run these tests, you need to set up the TEZOS_BINARIES environment variable to a directory that contains the binaries for all revisions needed by test (see below). The tests will be skipped if this variable isn’t set, and fail if the binaries aren’t available.

Building binaries for several revisions

Before running the tests, the user has to build the binaries and copy them to the right location. This can be done by the scripts/ script.

For instance, suppose we want to build binaries for two different revisions of zeronet:

A = b8de4297db6a681eb13343d2773c6840969a5537
B = 816625bed0983f7201e4c369440a910f006beb1a

TEZOS_HOME=~/tezos  # TEZOS repo, read-only access from the script
TEZOS_BINARIES=~/tezos-binaries  # where the binaries will be stored
TEZOS_BUILD=~/tmp/tezos_tmp  # where the binaries will be built

The following command will generate binaries for each of the specified branches in TEZOS_BINARIES.

scripts/ --clone $TEZOS_HOME --build-dir $TEZOS_BUILD \
                        --bin-dir $TEZOS_BINARIES \
                        b8de4297db6a681eb13343d2773c6840969a5537 \

tezos-accuser-003-PsddFKi3  tezos-baker-004-Pt24m4xi    tezos-node
tezos-accuser-004-Pt24m4xi  tezos-client                tezos-protocol-compiler
tezos-admin-client          tezos-endorser-003-PsddFKi3 tezos-signer
tezos-baker-003-PsddFKi3    tezos-endorser-004-Pt24m4xi

tezos-accuser-003-PsddFKi3  tezos-baker-004-Pt24m4xi    tezos-node
tezos-accuser-004-Pt24m4xi  tezos-client                tezos-protocol-compiler
tezos-admin-client          tezos-endorser-003-PsddFKi3 tezos-signer
tezos-baker-003-PsddFKi3    tezos-endorser-004-Pt24m4xi

Note: One can specify a branch instead of a revision but this is error-prone. For instance, protocols may have different hashes on different revisions on the same branch, and these hashes are typically hard-coded in the tests to activate the protocols.

Example 1:

The test uses two different revisions.

the sandbox_multibranch fixtures (which uses the SandboxMultibranch launcher) parameterized by a map that alternates between the two revisions.

The executables will be selected from revisions A and B as specified by:

A = "d272059bf474018d0c39f5a6e60634a95f0c44aa" # MAINNET
B = "6718e80254d4cb8d7ad86bce8cf3cb692550c6e7"  # MAINNET SNAPSHOT
MAP = {i:A if i % 2 == 0 else B  for i in range(20)}
@pytest.mark.parametrize('sandbox_multibranch', [MAP], indirect=True)

Run the test with

# mkdir tmp
pytest tests/multibranch/ --log-dir=tmp

Example 2: A full voting scenario

This tests uses binaries from revision b8de4297db6a681eb13343d2773c6840969a5537 and implements a full voting scenario (voting, launching a test chain and a test chain baker, upgrading to a new protocol, performing operations on the new protocol). It uses two protocols implemented by this specific revision,

ALPHA = 'PsddFKi32cMJ2qPjf43Qv5GDWLDPZb3T3bF6fLKiF5HtvHNU7aP'
NEW_PROTO = 'Pt24m4xiPbLDhVgVfABUjirbmda3yohdN82Sp9FeuAXJ4eV9otd'

as well the corresponding bakers tezos-baker-003-PsddFKi3 tezos-baker-004-Pt24m4xi.

scripts/ --clone $TEZOS_HOME --build-dir $TEZOS_BUILD \
    --bin-dir $TEZOS_BINARIES \ b8de4297db6a681eb13343d2773c6840969a5537

It can be run with

pytest tests/multibranch/`

Note: this test uses only one revision but it can’t run on branch master as we need an extra protocol with bakers.


There are few simple possible improvements.

  • Many client methods and client_output classes haven’t been implemented yet,
  • Be more consistent in the use of retries, timeout, to make tests less sensitive on timing assumption,
  • Implement new launchers (i.e. zeronet),
  • Use parametric fixtures more consistently: one can relaunch the same tests, with different parameters such as the number of peers,
  • Finish porting bash scripts,
  • improve typing annotations and mypy (typechecker) usage. Currently, only part of the code is type-checked.

Known issues

  • On rare occasions, some servers may not be properly killed upon test termination,
  • One some occasions, the timeout marker doesn’t play well with blocking client commmands. for instance, this may not stop the test if wait_for_inclusion is stuck.
def test_inclusion(self, sandbox, session):
    operation_hash = session['operation_hash']

The thread methods terminates the test but the resources aren’t properly cleaned up.

@pytest.mark.timeout(5, method='thread')

See discussion here.

To avoid this issue, one can use polling functions such as utils.check_contains_operations(client, [op_hash]) instead of using blocking commands.