This clever solution shows the need of random test cases.

This clever solution shows the need of random test cases.

I marked it as clever because I think that the goals of the kata is implement something to cache the function calls, aren't use a something already implemented.

I finished the kata now and had the same problem, it's not clear what "same nesting structures" means, because all the description examples uses integer values as nested structure, so makes sense to think that "same structure" are values of the same type. Do you agree?

Marking as resolved...

Marking as resolved...

The tests check if the function converted words with upper case letter to lower case, for example, an string "hello codeWars" should be "#HelloCodewars". This behavior of the tests aren't explicity said in the kata description. I think that the description must have this information.

I added it. Thanks for the attention.

I had rewrite the tests using the convention. Can you check it?

The only difference is because they write the it block inside an function, as a decorator. I will do it, thanks!

Error messages writed, can you check it?

In this situation, the function should return an empty dataframe too. I added this assertation:

df = pd.DataFrame([[1, 2]] * 3, columns = ["label-one", "label_two"])
test.expect(add_virtual_column(df, "label_one + label_two", "label").empty, "Should return an empty df when a df column is invalid")

So, I think that this is solved. Thanks!

and modifying the input will also affect the random tests.

In this point You're right. Because I do this:

df_result = add_virtual_column(df_valid, f"{df_valid.columns[0]}{operation}{df_valid.columns[1]}", new_label)
df_expected =  df_valid.copy()

Which can be a problem because add_virtual_column can affect the value of df_expected. Now I change the order of the statements:

df_expected =  df_valid.copy()
df_result = add_virtual_column(df_valid, f"{df_valid.columns[0]}{operation}{df_valid.columns[1]}", new_label)

Now it can't affect df_expected. This solve the problem, did it?