How to unittest the sequence of function calls made inside a python fuction?

Question

I would like to unittest a fuction and assert if the sequence of function calls made inside the function workflow(). Something like,

      [1st called] fetch_yeargroup_ls()
      [2nd called] invoke_get_links()....... 

I searched across many discussions but never found one answering my question.

Answer 1

If you are using mock you can create mocks as attributes of a parent mock, when patching out those functions:

try:
    # Python 3
    from unittest.mock import MagicMock, patch, call
except ImportError:
    # Python 2, install from PyPI first
    from mock import MagicMock, patch, call
import unittest

from module_under_test import function_under_test

class TestCallOrder(unittest.TestCase):
    def test_call_order(self):
        source_mock = MagicMock()
        with patch('module_under_test.function1', source_mock.function1), \
                patch('module_under_test.function2', source_mock.function2), \
                patch('module_under_test.function3', source_mock.function3)

            # the test is successful if the 3 functions are called in this
            # specific order with these specific arguments:
            expected = [
                call.function1('foo'),
                call.function2('bar'),
                call.function3('baz')
            ]

            # run your code-under-test
            function_under_test()

            self.assertEqual(source_mock.mock_calls, expected)

Because the 3 functions are attached to source_mock, all calls to them are recorded on the parent mock object in the Mock.mock_calls attribute and you can make assertions about their call order.

I attached the 3 function mocks simply by looking them up as attributes on the source_mock object, but you could also use the Mock.attach_mock() method to attach mocks you created in a different way to a parent.