Ruby unit test for a simple socket server

Question

I have a simple Socket server that listens on port 9000 and returns the reverse string to the clients.

require 'socket'

# Create the server using the Socket class
server_socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
# Set the socket addres
sockaddr = Socket.pack_sockaddr_in(9000, 'localhost')

# Bind the socket address to the server socket
server_socket.bind(sockaddr)

# set the state to listen
server_socket.listen(5)
loop do
  client, client_sockaddr = server_socket.accept
  client.puts 'Connected to the server! Press q to exit'

  loop do
    # Receive data using recvfrom method on the new client socket
    data = client.recvfrom(1024)[0].chomp

    if data == 'q'
      client.close
      break
    else
      # Reverse the string
      respond = data.reverse

      # Send the respond
      client.puts "Your string in reverse is: #{respond}"
    end
  end
end

Now I want to write unit tests for this server to demonstrate the correctness of the response. I have no idea how to start. Looked at Rspec test and built-in Test::Unit module but could not figure it out. I know I can use RSpec Mocks or things like that but I am not even sure how where to put my test file and how to test my code.

Answer 1

I am not even sure where to put my test file and how to test my code.

You can put your test file anywhere you want; you just need include the path to your server (and client) at the top of your rpsec file. For the following example, I put all the files in the same directory.

$ tree sockets
sockets
├── my_client.rb
├── my_server.rb
├── my_specs.rb
└── prog.rb  #<==creates a client and server to see if they work

my_client.rb:

require 'socket'

class MyClient
  attr_reader :socket

  def initialize
    @socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
    @socket.setsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR, true)
    @socket.connect Socket.pack_sockaddr_in(13_500, '127.0.0.1')
  end

  def send_data(data)
    @socket.puts data
  end

  def recv_data
    @socket.gets
  end

end

my_server.rb:

require 'socket'

class MyServer
  attr_reader :server_socket, :client

  def initialize
    @server_socket = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM, 0)
    @server_socket.setsockopt(Socket::SOL_SOCKET,Socket::SO_REUSEADDR, true)

    sockaddr = Socket.pack_sockaddr_in(13_500, '127.0.0.1')
    @server_socket.bind(sockaddr)
    @server_socket.listen(5)
  end

  def start
    #Blocks and waits for client connections:
    @client, client_sockaddr = @server_socket.accept
    @client.puts "Connected to the server! Press q to exit"

    loop do # loop() automatically catches a StopIteration exception and terminates
      data = @client.recvfrom(1024)[0].chomp
      handle_data(data)
    end
  end

  def handle_data data
    case data
    when 'q', ''
      raise StopIteration  #terminates loop()
    else 
      if @client  #For some reason @client can be nil here
                  #which causes a nil.puts error two lines down.
        response = data.reverse
        @client.puts "Your string in reverse is: #{response}"
      end
    end

      response
  end


end

prog.rb:

require_relative 'my_server.rb'
require_relative 'my_client.rb'

server = MyServer.new

Thread.new do
  server.start
end

sleep 1  #Otherwise, get connection refused error because client sends
         #data to server before server creates the client socket

client = MyClient.new
greeting = client.recv_data
puts greeting

client.send_data("hello")
response = client.recv_data
puts response

client.socket.close
server.server_socket.close
server.client.close

my_specs.rb:

require_relative 'my_server'  #relative path to server
require_relative 'my_client'  #relative path to client

describe MyServer do 

  before(:example) do
    @server = MyServer.new

    Thread.new do
      @server.start
    end

    sleep 1  #Allow server to start, so client doesn't send data 
             #to the server before the server creates the socket.

    @client = MyClient.new
    @data = 'hello'
    @client.send_data @data  #Make sure server has started before doing this.
  end

  after(:example) do
    @server.server_socket.close #Will send nil to client, causing gets() to unblock,
                 #allowing recv_data() to finish executing.
    @server.client.close
    @client.socket.close  
  end

  describe '#handle_data' do
    context 'given a string' do
      it "returns reversed string" do
        expect(@server.handle_data(@data)).to eql(@data.reverse)
      end
    end
  end

  describe '- client receives correct response' do
    context 'given a string' do
      it "returns reversed string" do
        greeting = @client.recv_data
        expect(@client.recv_data).to eql("Your string in reverse is: #{@data.reverse}\n")
      end
    end
  end

end

Run the specs:

~/ruby_programs/sockets$ rspec my_specs.rb
..

Finished in 2.01 seconds (files took 0.11932 seconds to load)
2 examples, 0 failures