Add assert_one_of

[yngvar-antonsson]

Add assert_one_of to assert that the value is one of several alternatives.
It could be useful to write tests that support several tarantool versions.

[DifferentialOrange]

I don't quite get why I was summoned to review luatest PR since I never contributed here and don't know how the infrastructure works, but the patch seems fine.

You can also think about unifying the code with assert_covers since they do similar things.

[Totktonada]

AFAIK we generaly follow the LuaUnit assertion naming (but just snake case variants). There are assert_table_contains and assert_not_table_contains (code).

[DifferentialOrange]

AFAIK we generaly follow the LuaUnit assertion naming (but just snake case variants). There are assert_table_contains and assert_not_table_contains (code).

For me, assert_table_contains and assert_one_of have different ideas, even though their implementation is the same.

[Totktonada]

BTW, the implementation is not exactly same. You're using ipairs(), so the function is applicable only for array alike tables. However, LuaUnit uses pairs() and so it makes the function applicable for tables like {foo = 'needle', bar = 'unrelated'}.

Regarding assert_one_of name semantic: if the idea is to check that the given element is present in the given table exactly one time, the implementation doesn't check it.

However, I still think that LuaUnit names are good enough and I see no reason to use different ones.

[yngvar-antonsson]

As for me assertTableContains( {'a', 'b', 'c', 'd'}, 'b' ) != assert_one_of('b', {'a', 'b'}). I would leave it as is, but maybe we could think about something like assert_one_of_many or something like that.