great solution! I like it, man!

This is surely clever, but probably shouldn't be used or marked as best practice. I'd have to performance test to be sure, but allocating an array on heap seems like it would be much slower than a branch with no array allocation. Maybe I'm wrong, in which case this would be a nice answer, but the bitwise and will always be better for both performance and readability.

Use assert_equals

hahaha really cool solution :D

• uses test_expect
• you basically eed to wrap a built-in function

...plus all the below issues

Convert integer numbers to binary, without using the to_s(2) method.

1. There's no check for to_s(2) (see this)
2. No random tests

There should be some tests with the minimum width less than the number of digits. Random tests would be nice too.

This seems resolved now : "The second optional argument passes the minimum length. If your binary number is shorter than this length, then pad zeros on the left hand side to fulfill this minimum length ... "

I'm literally days in learning Ruby, and this simple solution has already taught me so much and made me think of so many more things that could be done with this concept, THANK YOU

Since it's explicitly mentioned in the description, there should be a test to check that String#to_i(int) isn't used.

Needs random tests

Also base conversion is a duplicate

According to the description, the second argument is the number of leading zeros, but the tests treat it as a full string length including other digits.