You must have run through the standard codebuild setup as described in the root README. This will make sure you have all the dependencies installed correctly. The integration test dependencies are:

• s2nc and s2nd (should be in the bin/ directory)
• libs2n (should be in the lib/ directory)
• openssl (based on the S2N_LIBCRYPTO env var)
• tox
• Compiled Java SSLSocketClient for the Java provider
• Compiled an s2nc executable named s2nc_head in the bin directory for the cross compatibility test

Alternately, you can use the "best effort" mode with uv. This will only run the integration tests with the currently available binaries.

# install uv
curl -LsSf https://astral.sh/uv/install.sh | sh
# run pytest
# -x: exit on the first failure
# -rpfs: print a (r)eport with (p)assing, (f)ailed, and (s)kipped tests.
uv run pytest --provider-version <LINKED_LIBCRYPTO> --best-effort-NOT-FOR-CI -x -rpfs -n auto

 ┌────────────────────────────────────────────────────────────┐
 │                                                            │
 │                      Pytest Process                        │
 │      Managed                                Managed        │
 │    Process (s2n)                          Process (Ossl)   │
 │     │       ▲                             │        ▲       │
 └─────┼───────┼─────────────────────────────┼────────┼───────┘
       │       │                             │        │        
     STDIN   STDOUT                        STDIN    STDOUT     
       │       │                             │        │        
       │       │                             │        │        
    ┌──▼───────┼───┐                      ┌──▼────────┼────┐   
    │    s2nc      │◄────────TLS─────────►│  openssl server│   
    └──────────────┘  ▲                   └────────────────┘   
                      │                           ▲            
                      │                           │            
                localhost/socket                  │            
                                               process         

The integration test harness relies on client and server executables. It coordinates these through stdin/stdout.

The above diagram shows an example setup with s2nc as the client and openssl as the server. Note that these are just for the purpose of documentation, and the actual integration tests run with a wide variety of executables.

The fastest way to run the integrationv2 tests is to run make from the S2N root directory.

ubuntu@host:s2n_root/ $ make -C tests/integrationv2 all

The Makefile automatically sets your PATH and LD_LIBRARY_PATH environment. It will execute tox to setup your Python environment. Then all the integration tests will be collected and executed.

Note If you are running the dynamic record size test you will need to use sudo.

If you only want to run a single test, you can set the TOX_TEST_NAME environment variable:

ubuntu@host:s2n_root/ $ TOX_TEST_NAME=test_happy_path make -C tests/integrationv2

Multiple specific tests can also be run as follows:

ubuntu@host:s2n_root/ $ TOX_TEST_NAME="test_happy_path test_sslyze" make -C tests/integrationv2

The happy path test combines thousands of parameters, and has to validate that the combinations match. Below is a simple test that demonstrates how lists of parameters are combined to test all possible parameter combinations.

import copy
import pytest

from configuration import available_ports, ALL_CERTS
from common import ProviderOptions, Cert, Ciphers, Protocols
from fixtures import managed_process
from providers import Provider, S2N, OpenSSL
from utils import get_parameter_name, get_expected_s2n_version


"""
Pytest will generate 8 configuration based on the parameterize options below. The
test will be run with each of the possible configurations.
"""

@pytest.mark.parametrize("cipher",
    [Ciphers.AES128_GCM_SHA256, Ciphers.CHACHA20_POLY1305_SHA256], ids=get_parameter_name)
@pytest.mark.parametrize("provider",
    [S2N, OpenSSL])
@pytest.mark.parametrize("protocol",
    [Protocols.TLS13], ids=get_parameter_name)
@pytest.mark.parametrize("certificate",
    [Cert("ECDSA_256", "ecdsa_p256_pkcs1"), Cert("ECDSA_384", "ecdsa_p384_pkcs1")], ids=get_parameter_name)
def test_example(managed_process, cipher, provider, protocol, certificate):
    host = "localhost"
    port = next(available_ports)

    client_options = ProviderOptions(
        mode=Provider.ClientMode,
        host="localhost",
        port=port,
        cipher=cipher,
        insecure=True,
        protocol=protocol)

    server_options = copy.copy(client_options)
    server_options.mode = Provider.ServerMode
    server_options.key = certificate.key
    server_options.cert = certificate.cert

    expected_version = get_expected_s2n_version(protocol, provider)

    server = managed_process(provider, server_options, timeout=5)
    client = managed_process(S2N, client_options, timeout=5)

    for results in client.get_results():
        assert results.exception is None
        assert results.exit_code == 0
        assert bytes("Actual protocol version: {}".format(expected_version).encode('utf-8')) in results.stdout

    for results in server.get_results():
        assert results.exception is None
        assert results.exit_code == 0

If you are testing a new feature you need to determine how to use that feature with all supported providers.

You may have to add a command line flag to s2nc.c or s2nd.c for your feature. Use long options if possible, and use the same option name in both s2nc.c and s2nd.c. If you are able to use an option name similar to the OpenSSL name, please do. This reduces complexity across TLS providers.

An example of similar naming is '-reconnect' in OpenSSL and '-r' in S2N. Both have a hardcoded value of 5 reconnects. The point is to remove logic from the test, and make the providers act as similar as possible.

If you are testing a feature which is similar across all TLS providers, add an option to the ProviderOptions object in common.py. If this feature is specific to a single provider, you can use the extra_flags option.

For example, to test the session resumption feature we need to tell various clients and servers to resume a session multiple times. To do this we added the 'reconnect' and 'reconnects_before_exit' options to the ProviderOptions object. But with the dynamic threshold feature we simply pass the '-D' argument as an extra_flag to s2n.

In each provider that supports your feature you need to check if the flag is set, and create a command line option for that particular provider. You can also add logic checks, e.g with client authentication the client must have a certificate to send. Otherwise the test will fail.

There are several optional arguments in the managed_process function. Use these arguments to have a greater level of control over how peers send test data. The argument send_marker can be used in parallel with the data_to_send Provider options. If both of these arguments are lists, the process will only write a data_to_send element when it reads a corresponding send_marker element from the process's stdout or stderr. Additionally, the managed_process argument close_marker can be used to control when the process should shut down.

An example of how to test that the server and the client can send and receive application data:

    server_options.data_to_send = ["First server message", "Second server message"]
    server_send_marker = ["Ready to send data", "First client message"]
    server_close_marker = ["Second client message"]

    client_options.data_to_send = ["First client message", "Second client message"]
    client_send_marker = ["Ready to send data", "First server message"]
    client_close_marker = ["Second server message"]

    server = managed_process(provider, server_options, server_send_marker, server_close_marker, timeout=5)
    client = managed_process(S2N, client_options, client_send_marker, client_close_marker, timeout=5)

INTERNALERROR> OSError: cannot send to An error similar to this is caused by a runtime error in a test. In tox.ini change -n8 to -n0 to see the actual error causing the OSError.