thank u

Read the posts below, it's been asked and answered before.

Couldn't understand
[1,[1,1]] not same as [[2,2],2] and[1,'[',']'] same as ['[',']',1]
Anyone can explain why [1,'[',']'] same as ['[',']',1]?

This issue of 'no sample tests' is already raised below, no need to create multiple of them. Until they're added, just click 'Attempt'.

Test Driven Development (TDD)

From Ruby 3.0, RSpec is used under the hood.

See https://rspec.info/

Defaults to the global describe for backwards compatibility, but RSpec.desribe works as well.

describe "Example" do
it "should return the sum" do
expect(add(1, 1)).to eq(2)
# The following is still supported, but new tests should now use them.
# Test.assert_equals(add(1, 1), 2)
end
end

Time: 518ms Passed: 0Failed: 1Errors: 1
Test Results:
Example
should return the sum
#<NoMethodError: undefined method add' for main:Object> main.rb:24:in block (2 levels) in '
/runner/frameworks/ruby/cw-2.rb:180:in wrap_error' /runner/frameworks/ruby/cw-2.rb:72:in it'
/runner/frameworks/ruby/cw-2.rb:206:in it' main.rb:23:in block in '
/runner/frameworks/ruby/cw-2.rb:55:in block in describe' /runner/frameworks/ruby/cw-2.rb:46:in measure'
/runner/frameworks/ruby/cw-2.rb:51:in describe' /runner/frameworks/ruby/cw-2.rb:202:in describe'
main.rb:22:in `'

I focused on block.thank u so much

From a glance: the last column has two 5s.
In any case, this is not a kata issue. Your code is buggy.