Multiple things wrong is not tested for 1 element inputs.

1 element input with two different foods (e.g Fish and more chips) is not tested either.

There are no random tests.

Should be updated to Ruby 3 and have it blocks fixed.

• More fixed tests for negative start_index && interval should be added

• Ruby 3.0 should be enabled (Refer this & this for more detail)

Markdown formatting is broken.

( JS )

Lacks Example tests

The test failure messages should show the inputs that failed.

JavaScript translation

In the C# the initial setup teaches users a bad way of using C#, instead it should utilize method overloads and the initial code should look something like this:

using System;
using System.Collections.Generic;
using System.Linq;

public static class Kata
{
  public static IEnumerable<T> Every<T>(this IEnumerable<T> arr, int interval, int start)
  {
    throw new NotImplementedException();
  }
  
  public static IEnumerable<T> Every<T>(this IEnumerable<T> arr, int interval)
  {
    throw new NotImplementedException();
  }
    
  public static IEnumerable<T> Every<T>(this IEnumerable<T> arr)
  {
    throw new NotImplementedException();
  }
}

Please add sample tests for Ruby version.