Pytest-drf unit tests and dict_items assert - pytest

Question

There is a code in a legacy project using pytest-drf and I'm new in Python and tests, I would like to know what an assert checking two dict_items is comparing, but could not find out neither other examples nor explanations about it.
Here's the code:
#pytest.mark.django_db
class TestPhones(Base)
list_url = lambda_fixture(lambda: url_for('phones-list'))
detail_url = lambda_fixture(
lambda old_phone: url_for('phones-detail', old_phone.pk))
class TestCreate(VerbTests.Create):
data = phone_json
def test_returned_json(self, data, json, model):
expected = data.items()
actual = json.items()
assert expected <= actual
What is this assert code doing?
I couldn't understand why it's being used the lower symbol '<' for this assert, I see that it's comparing dict_items content in 'expected' and 'actual' received from the API in json format, but couldn't find what's going on.

Answer 1

assert <condition> is used to check that an expected condition is fulfilled.
For more information on the testing and especially on assert, you can have a look on Pytest documentation
While comparing the dictionaries, dict1<=dict2 returns True if dict1 is contained in dict2.
Here a code which show the different cases:
my_dict = {"test1":"test_val1", "test2":"test_val2", "test3":"test_val3", "test4":"test_val4", "test5":"test_val5"}
for my_tuple in [
(["test1", "test2"], ["test1", "test5"]),
(["test1", "test2"], ["test1", "test2"]),
(["test1", "test2"], ["test1"]),
(["test1"], ["test1", "test5"]),
]:
my_dict1 = {}
my_dict2 = {}
for key in my_tuple[0]:
my_dict1[key] = my_dict[key]
for key in my_tuple[1]:
my_dict2[key] = my_dict[key]
print(my_dict1.items() <= my_dict2.items(), "---", my_dict1, "<=", my_dict2)
The returned output
False --- {'test1': 'test_val1', 'test2': 'test_val2'} <= {'test1': 'test_val1', 'test5': 'test_val5'} # not contained
True --- {'test1': 'test_val1', 'test2': 'test_val2'} <= {'test1': 'test_val1', 'test2': 'test_val2'} # equal
False --- {'test1': 'test_val1', 'test2': 'test_val2'} <= {'test1': 'test_val1'} # not contained
True --- {'test1': 'test_val1'} <= {'test1': 'test_val1', 'test5': 'test_val5'} # contained