Kata

If a new table is required, this should be tested.

What does it mean? All test cases test the result of the function, which is the new table. Therefore, why this isn't tested? Did you said a test case to test if the input aren't changed?

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?

Did you said a test case to test if the input aren't changed?

Yup

Make sense that role can be values as 2 or label_one + 1. But hadn't added this in the kata's requirement because it would add more complexity to te kata's. Therefore, the goal of the kata's is deal only with roles of the form: {label_one} {operation} {label_two}. So I don't think that what you said is a problem, is only a kata's design decision.

What do you think?

I will write it. Thanks

But, in the codewars documentation about codewars test framework are used describe/it blocks. So, why this is an old style? and what is the "correct" style?

That is the right link. Can you not see the difference between your code and what's written there?

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

I don't undestand. I explicity imported the test framework, see:

import codewars_test as test

Are you asking to import explicitly the solution instead of use *? Like this:

from solution import add_virtual_column

Is it?

Sample tests aren't importing anything. And yes, don't use import *.

Sorry. I don't have seen the error. I fixed it. Can you check?