Like many software projects, Salt has two broad-based testing approaches -- integration testing and unit testing. While integration testing focuses on the interaction between components in a sandboxed environment, unit testing focuses on the singular implementation of individual functions.
Unit tests should be used specifically to test a function's logic. Unit tests rely on mocking external resources.
While unit tests are good for ensuring consistent results, they are most useful when they do not require more than a few mocks. Effort should be made to mock as many external resources as possible. This effort is encouraged, but not required. Sometimes the isolation provided by completely mocking the external dependencies is not worth the effort of mocking those dependencies.
In these cases, requiring an external library to be installed on the system before running the test file is a useful way to strike this balance. For example, the unit tests for the MySQL execution module require the presence of the MySQL python bindings on the system running the test file before proceeding to run the tests.
Overly detailed mocking can also result in decreased test readability and brittleness as the tests are more likely to fail when the code or its dependencies legitimately change. In these cases, it is better to add dependencies to the test runner dependency state.
This guide assumes that your Salt development environment is already configured and that you have a basic understanding of contributing to the Salt codebase. If you're unfamiliar with either of these topics, please refer to the Installing Salt for Development and the Contributing pages, respectively.
This documentation also assumes that you have an understanding of how to run Salt's test suite, including running the unit test subsection, running the unit tests without testing daemons to speed up development wait times, and running a unit test file, class, or individual test.
Unit tests should be written to the following specifications.
Since unit testing focuses on the singular implementation of individual functions, unit tests should be used specifically to test a function's logic. The following guidelines should be followed when writing unit tests for Salt's test suite:
raise
and return
statement needs to be independently tested.A reasonable effort needs to be made to mock external resources used in the code being tested, such as APIs, function calls, external data either globally available or passed in through function arguments, file data, etc.
Test names and docstrings should indicate what functionality is being tested.
Test functions are named test_<fcn>_<test-name>
where <fcn>
is the function
being tested and <test-name>
describes the raise
or return
being tested.
Unit tests for salt/.../<module>.py
are contained in a file called
tests/unit/.../<module>_test.py
, e.g. the tests for salt/modules/fib.py
are in tests/unit/modules/fib_test.py
.
In order for unit tests to get picked up during a run of the unit test suite, each
unit test file must be appended with _test.py
and each individual test must be
prepended with the test_
naming syntax, as described above.
If a function does not start with test_
, then the function acts as a "normal"
function and is not considered a testing function. It will not be included in the
test run or testing output. The same principle applies to unit test files that
do not have the _test.py
naming syntax. This test file naming convention is
how the test runner recognizes that a test file contains unit tests.
Most commonly, the following imports are necessary to create a unit test:
# Import Salt Testing libs
from salttesting import skipIf, TestCase
from salttesting.helpers import ensure_in_syspath
If you need mock support to your tests, please also import:
from salttesting.mock import NO_MOCK, NO_MOCK_REASON, MagicMock, patch, call
A longer discussion on the types of assertions one can make can be found by reading Python's documentation on unit testing.
In many cases, the purpose of a Salt module is to interact with some external system, whether it be to control a database, manipulate files on a filesystem or something else. In these varied cases, it's necessary to design a unit test which can test the function whilst replacing functions which might actually call out to external systems. One might think of this as "blocking the exits" for code under tests and redirecting the calls to external systems with our own code which produces known results during the duration of the test.
To achieve this behavior, Salt makes heavy use of the MagicMock package.
To understand how one might integrate Mock into writing a unit test for Salt, let's imagine a scenario in which we're testing an execution module that's designed to operate on a database. Furthermore, let's imagine two separate methods, here presented in pseduo-code in an imaginary execution module called 'db.py.
def create_user(username):
qry = 'CREATE USER {0}'.format(username)
execute_query(qry)
def execute_query(qry):
# Connect to a database and actually do the query...
Here, let's imagine that we want to create a unit test for the create_user function. In doing so, we want to avoid any calls out to an external system and so while we are running our unit tests, we want to replace the actual interaction with a database with a function that can capture the parameters sent to it and return pre-defined values. Therefore, our task is clear -- to write a unit test which tests the functionality of create_user while also replacing 'execute_query' with a mocked function.
To begin, we set up the skeleton of our class much like we did before, but with additional imports for MagicMock:
# Import Salt Testing libs
from salttesting import TestCase
# Import Salt execution module to test
from salt.modules import db
# Import Mock libraries
from salttesting.mock import NO_MOCK, NO_MOCK_REASON, MagicMock, patch, call
# Create test case class and inherit from Salt's customized TestCase
# Skip this test case if we don't have access to mock!
@skipIf(NO_MOCK, NO_MOCK_REASON)
class DbTestCase(TestCase):
def test_create_user(self):
# First, we replace 'execute_query' with our own mock function
db.execute_query = MagicMock()
# Now that the exits are blocked, we can run the function under test.
db.create_user('testuser')
# We could now query our mock object to see which calls were made
# to it.
## print db.execute_query.mock_calls
# Construct a call object that simulates the way we expected
# execute_query to have been called.
expected_call = call('CREATE USER testuser')
# Compare the expected call with the list of actual calls. The
# test will succeed or fail depending on the output of this
# assertion.
db.execute_query.assert_has_calls(expected_call)
__salt__
In Place¶At times, it becomes necessary to make modifications to a module's view of
functions in its own __salt__
dictionary. Luckily, this process is quite
easy.
Below is an example that uses MagicMock's patch
functionality to insert a
function into __salt__
that's actually a MagicMock instance.
def show_patch(self):
with patch.dict(my_module.__salt__,
{'function.to_replace': MagicMock()}:
# From this scope, carry on with testing, with a modified __salt__!
Let's assume that we're testing a very basic function in an imaginary Salt
execution module. Given a module called fib.py
that has a function called
calculate(num_of_results)
, which given a num_of_results
, produces a list of
sequential Fibonacci numbers of that length.
A unit test to test this function might be commonly placed in a file called
tests/unit/modules/fib_test.py
. The convention is to place unit tests for
Salt execution modules in test/unit/modules/
and to name the tests module
suffixed with _test.py
.
Tests are grouped around test cases, which are logically grouped sets of tests
against a piece of functionality in the tested software. Test cases are created
as Python classes in the unit test module. To return to our example, here's how
we might write the skeleton for testing fib.py
:
# Import Salt Testing libs
from salttesting import TestCase
# Import Salt execution module to test
from salt.modules import fib
# Create test case class and inherit from Salt's customized TestCase
class FibTestCase(TestCase):
'''
This class contains a set of functions that test salt.modules.fib.
'''
def test_fib(self):
'''
To create a unit test, we should prefix the name with `test_' so
that it's recognized by the test runner.
'''
fib_five = (0, 1, 1, 2, 3)
self.assertEqual(fib.calculate(5), fib_five)
At this point, the test can now be run, either individually or as a part of a full run of the test runner. To ease development, a single test can be executed:
tests/runtests.py -v -n unit.modules.fib_test
This will report the status of the test: success, failure, or error. The
-v
flag increases output verbosity.
tests/runtests.py -n unit.modules.fib_test -v
To review the results of a particular run, take a note of the log location given in the output for each test:
Logging tests on /var/folders/nl/d809xbq577l3qrbj3ymtpbq80000gn/T/salt-runtests.log
Consider the following function from salt/modules/linux_sysctl.py.
def get(name):
'''
Return a single sysctl parameter for this minion
CLI Example:
.. code-block:: bash
salt '*' sysctl.get net.ipv4.ip_forward
'''
cmd = 'sysctl -n {0}'.format(name)
out = __salt__['cmd.run'](cmd)
return out
This function is very simple, comprising only four source lines of code and
having only one return statement, so we know only one test is needed. There
are also two inputs to the function, the name
function argument and the call
to __salt__['cmd.run']()
, both of which need to be appropriately mocked.
Mocking a function parameter is straightforward, whereas mocking a function
call will require, in this case, the use of MagicMock. For added isolation, we
will also redefine the __salt__
dictionary such that it only contains
'cmd.run'
.
# Import Salt Libs
from salt.modules import linux_sysctl
# Import Salt Testing Libs
from salttesting import skipIf, TestCase
from salttesting.helpers import ensure_in_syspath
from salttesting.mock import (
MagicMock,
patch,
NO_MOCK,
NO_MOCK_REASON
)
ensure_in_syspath('../../')
# Globals
linux_sysctl.__salt__ = {}
@skipIf(NO_MOCK, NO_MOCK_REASON)
class LinuxSysctlTestCase(TestCase):
'''
TestCase for salt.modules.linux_sysctl module
'''
def test_get(self):
'''
Tests the return of get function
'''
mock_cmd = MagicMock(return_value=1)
with patch.dict(linux_sysctl.__salt__, {'cmd.run': mock_cmd}):
self.assertEqual(linux_sysctl.get('net.ipv4.ip_forward'), 1)
if __name__ == '__main__':
from integration import run_tests
run_tests(LinuxSysctlTestCase, needs_daemon=False)
Since get()
has only one raise or return statement and that statement is a
success condition, the test function is simply named test_get()
. As
described, the single function call parameter, name
is mocked with
net.ipv4.ip_forward
and __salt__['cmd.run']
is replaced by a MagicMock
function object. We are only interested in the return value of
__salt__['cmd.run']
, which MagicMock allows us by specifying via
return_value=1
. Finally, the test itself tests for equality between the
return value of get()
and the expected return of 1
. This assertion is
expected to succeed because get()
will determine its return value from
__salt__['cmd.run']
, which we have mocked to return 1
.
Now consider the assign()
function from the same
salt/modules/linux_sysctl.py source file.
def assign(name, value):
'''
Assign a single sysctl parameter for this minion
CLI Example:
.. code-block:: bash
salt '*' sysctl.assign net.ipv4.ip_forward 1
'''
value = str(value)
sysctl_file = '/proc/sys/{0}'.format(name.replace('.', '/'))
if not os.path.exists(sysctl_file):
raise CommandExecutionError('sysctl {0} does not exist'.format(name))
ret = {}
cmd = 'sysctl -w {0}="{1}"'.format(name, value)
data = __salt__['cmd.run_all'](cmd)
out = data['stdout']
err = data['stderr']
# Example:
# # sysctl -w net.ipv4.tcp_rmem="4096 87380 16777216"
# net.ipv4.tcp_rmem = 4096 87380 16777216
regex = re.compile(r'^{0}\s+=\s+{1}$'.format(re.escape(name),
re.escape(value)))
if not regex.match(out) or 'Invalid argument' in str(err):
if data['retcode'] != 0 and err:
error = err
else:
error = out
raise CommandExecutionError('sysctl -w failed: {0}'.format(error))
new_name, new_value = out.split(' = ', 1)
ret[new_name] = new_value
return ret
This function contains two raise statements and one return statement, so we
know that we will need (at least) three tests. It has two function arguments
and many references to non-builtin functions. In the tests below you will see
that MagicMock's patch()
method may be used as a context manager or as a
decorator.
There are three test functions, one for each raise and return statement in the source function. Each function is self-contained and contains all and only the mocks and data needed to test the raise or return statement it is concerned with.
# Import Salt Libs
from salt.modules import linux_sysctl
from salt.exceptions import CommandExecutionError
# Import Salt Testing Libs
from salttesting import skipIf, TestCase
from salttesting.helpers import ensure_in_syspath
from salttesting.mock import (
MagicMock,
patch,
NO_MOCK,
NO_MOCK_REASON
)
ensure_in_syspath('../../')
# Globals
linux_sysctl.__salt__ = {}
@skipIf(NO_MOCK, NO_MOCK_REASON)
class LinuxSysctlTestCase(TestCase):
'''
TestCase for salt.modules.linux_sysctl module
'''
@patch('os.path.exists', MagicMock(return_value=False))
def test_assign_proc_sys_failed(self):
'''
Tests if /proc/sys/<kernel-subsystem> exists or not
'''
cmd = {'pid': 1337, 'retcode': 0, 'stderr': '',
'stdout': 'net.ipv4.ip_forward = 1'}
mock_cmd = MagicMock(return_value=cmd)
with patch.dict(linux_sysctl.__salt__, {'cmd.run_all': mock_cmd}):
self.assertRaises(CommandExecutionError,
linux_sysctl.assign,
'net.ipv4.ip_forward', 1)
@patch('os.path.exists', MagicMock(return_value=True))
def test_assign_cmd_failed(self):
'''
Tests if the assignment was successful or not
'''
cmd = {'pid': 1337, 'retcode': 0, 'stderr':
'sysctl: setting key "net.ipv4.ip_forward": Invalid argument',
'stdout': 'net.ipv4.ip_forward = backward'}
mock_cmd = MagicMock(return_value=cmd)
with patch.dict(linux_sysctl.__salt__, {'cmd.run_all': mock_cmd}):
self.assertRaises(CommandExecutionError,
linux_sysctl.assign,
'net.ipv4.ip_forward', 'backward')
@patch('os.path.exists', MagicMock(return_value=True))
def test_assign_success(self):
'''
Tests the return of successful assign function
'''
cmd = {'pid': 1337, 'retcode': 0, 'stderr': '',
'stdout': 'net.ipv4.ip_forward = 1'}
ret = {'net.ipv4.ip_forward': '1'}
mock_cmd = MagicMock(return_value=cmd)
with patch.dict(linux_sysctl.__salt__, {'cmd.run_all': mock_cmd}):
self.assertEqual(linux_sysctl.assign(
'net.ipv4.ip_forward', 1), ret)
if __name__ == '__main__':
from integration import run_tests
run_tests(LinuxSysctlTestCase, needs_daemon=False)