pyhamcrest - Compare two list

Question

I've just started learning python. Currently writing a unit test to assert if the elements in the expected list is present in the actual list

def test_compare_list_of_items():
    actual_list_of_items = ['a','b']
    expected_list_of_items = ['a']

    assert_that(actual_list_of_items, has_item(has_items(expected_list_of_items)))

but i'm getting errors like

E    Expected: a sequence containing (a sequence containing <['a']>)
E         but: was <['a', 'b']>

How and what sequence matcher should i use in order to assert if item 'a' in the expected list is present in the actual list?

`has_items` match if all given items appear in the sequence, in any order https://github.com/hamcrest/PyHamcrest — k10, Dec 30 '19 at 22:38
sounds like you might be using the wrong function in that library then — gold_cy, Dec 30 '19 at 22:55
@aws_apprentice - Would appreciate, if you could let me know the right function from the available list. — k10, Dec 30 '19 at 23:07

score 3 · Answer 1 · answered Dec 30 '19 at 23:26

3

You are using has_item when you should only be using has_items. According to the docs this takes multiple matchers which is what you want. Your function then becomes

def test_compare_list_of_items():
    actual_list_of_items = ['a','b']
    expected_list_of_items = ['a']

    assert_that(actual_list_of_items, has_items(*expected_list_of_items))

We use iterable unpacking for the list to feed as the arguments and now when you run it, it shouldn't error out.

answered Dec 30 '19 at 23:26

gold_cy

13,648
3
23
45

Thanks! I tried that earlier but it doesn't work: ```def test_compare_list_of_items(): actual_list_of_items = ['a','b'] expected_list_of_items = ['a'] > assert_that(actual_list_of_items, has_items(expected_list_of_items)) E AssertionError: E Expected: (a sequence containing <['a']>) E but: a sequence containing <['a']> was <['a', 'b']>``` – k10 Dec 30 '19 at 23:29
you're missing the `*`, please copy my answer directly how it is, the issue is that you aren't _unpacking_ the list, note the `*` directly in front of `expected_list_of_items` – gold_cy Dec 30 '19 at 23:32
Oh ok! Thanks a lot @aws_apprentice. I read the document again and now i got what you were trying to say above. This helped a lot – k10 Dec 30 '19 at 23:36

score 0 · Answer 2 · answered Dec 30 '19 at 22:51

0

I don't know about has_items function, but can you just use something like this?

assertTrue(all(item in expected_list_of_items for item in actual_list_of_items))

answered Dec 30 '19 at 22:51

marcos

4,473
1
10
24

Thanks Marcos! I do have a work around but i want to use pyhamcrest matchers and hence the question. Any help would be appreciated – k10 Dec 30 '19 at 23:16

pyhamcrest - Compare two list

2 Answers2