Alternative for https://www.codewithjason.com/test-ruby-methods-involve-puts-gets/

example_spec.rb

class Example
  def initialize(input: $stdin, output: $stdout)
    @input = input
    @output = output
  end

  def ask_for_number
    @output.puts "Input an integer 5 or above"
    loop do
      input = @input.gets.to_i
      return true if input >= 5
      @output.puts "Invalid. Try again:"
    end
  end
end

require 'stringio'

RSpec.describe Example do
  context 'with input greater than 5' do
    it 'asks for input only once' do
      output = ask_for_number_with_input(6)

      expect(output).to eq "Input an integer 5 or above\n"
    end
  end

  context 'with input equal to 5' do
    it 'asks for input only once' do
      output = ask_for_number_with_input(5)

      expect(output).to eq "Input an integer 5 or above\n"
    end
  end

  context 'with input less than 5' do
    it 'asks repeatedly, until a number 5 or greater is provided' do
      output = ask_for_number_with_input(2, 3, 6)

      expect(output).to eq <<~OUTPUT
        Input an integer 5 or above
        Invalid. Try again:
        Invalid. Try again:
      OUTPUT
    end
  end

  def ask_for_number_with_input(*input_numbers)
    input = StringIO.new(input_numbers.join("\n") + "\n")
    output = StringIO.new

    example = Example.new(input: input, output: output)
    expect(example.ask_for_number).to be true

    output.string
  end
end