Rspec. When hashes are used inside arrays

I'm always amazed at the flexibility of unit testing when working with Ruby projects. Below are examples of such flexibility in which you can check the contents of hashes nested in an array.

context 'when hashes in array' do
  let(:hash_set) do
    [
      { attr1: 1, attr2: 2 },
      { attr1: 3, attr2: 4 }
    ]
  end

  let(:attribute_keys) { %i[attr1 attr2] }

  it 'contains a set of attribute keys' do
    expect(hash_set).to all(include(*attribute_keys))
  end
end

context 'when hashes in nested array' do
  let(:hash_set) do
    [
      { attr1: 1, attr2: [{ attr3: 3, attr4: 4 }] },
      { attr1: 5, attr2: [{ attr3: 6, attr4: 7 }] }
    ]
  end

  let(:first_attribute_keys) { %i[attr1 attr2] }
  let(:second_attribute_keys) { %i[attr3 attr4] }

  it 'contains a set of first attribute keys' do
    expect(hash_set).to all(include(*first_attribute_keys))
  end

  it 'contains a set of second attribute keys' do
    expect(hash_set).to all(
      include(attr2: all(include(*second_attribute_keys)))
    )
  end
end

# Some class for testing
class Tester
  def exec(options)
    # some work
  end
end

context 'when hashes are passed as parameters' do
  subject(:tester) { Tester.new }

  let(:options) do
    {
      attr1: 1,
      attr2: { attr4: 2 },
      attr3: [
        { attr5: 3 },
        { attr6: 4 }
      ]
    }
  end

  it 'contains a set of attribute keys with values' do
    expect(tester).to receive(:exec).with(
      hash_including(
        attr1: 1,
        attr2: hash_including(attr4: 2),
        attr3: [hash_including(attr5: 3), hash_including(attr6: 4)]
      )
    )

    tester.exec(options)
  end

  it 'contains a set of attribute keys' do
    expect(tester).to receive(:exec).with(
      hash_including(
        :attr1,
        attr2: hash_including(:attr4),
        attr3: array_including(hash_including(:attr5), hash_including(:attr6))
      )
    )

    tester.exec(options)
  end
end

Ruby. Messages from RuboCop about using predefined variables

Ruby has a lot of predefined variables. The one of them is $/. It is used as a universal substitution of newline symbol:

> numbers = ['one', 'two', 'three']
=> ["one", "two", "three"]

> numbers.join($/)
=> "one\ntwo\nthree"

> puts numbers.join($/)
one
two
three
=> nil

RuboCop is a Ruby code style checker (linter) and formatter based on the community-driven Ruby Style Guide. If you use it in your project, then it is possible that you will face with the next problem when using $/:

Prefer `$INPUT_RECORD_SEPARATOR` or `$RS` from the stdlib 'English' module
(don't forget to require it) over `$/`.(convention:Style/SpecialGlobalVars)

To fix it you can do like this:

# readable global var aliases
require 'English'

...
def log_error(error)
  backtrace_cleaner = ActiveSupport::BacktraceCleaner.new
  backtrace_cleaner.add_filter { |line| line.gsub(Rails.root.to_s, '') }
  backtrace_cleaner.add_silencer { |line| line =~ /puma|rubygems/ }

  Rails.logger.error(
    [
      "#{error.class}: #{error.message}",
      *backtrace_cleaner.clean(error.backtrace)
    ].join($RS)
  )
end
...

As you can see I have used the $RS. Instead, you can use $INPUT_RECORD_SEPARATOR.

Mathematical equivalence of bit shifts

a << b <=> a * (2 ^ b)
a >> b <=> a / (2 ^ b)

Apache Bench

The Apache software foundation offers a lot of cool tools. The one of them is Apache Bench. It gives you ability to test and get benchmarks of handling http requests by your web service. I currently use Ubuntu so to play around I ran next command:

sudo apt-get install apache2-utils

And fed my service to it:

ab -n 100 -c 10 http://127.0.0.1/greet

As a result, you'll get next output:

This is ApacheBench, Version 2.3 <$Revision: 1807734 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 127.0.0.1 (be patient).....done


Server Software:        nginx/1.17.6
Server Hostname:        127.0.0.1
Server Port:            80

Document Path:          /greet
Document Length:        10 bytes

Concurrency Level:      10
Time taken for tests:   0.004 seconds
Complete requests:      100
Failed requests:        0
Total transferred:      15300 bytes
HTML transferred:       1000 bytes
Requests per second:    27956.39 [#/sec] (mean)
Time per request:       0.358 [ms] (mean)
Time per request:       0.036 [ms] (mean, across all concurrent requests)
Transfer rate:          4177.08 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:     0    0   0.0      0       0
Waiting:        0    0   0.0      0       0
Total:          0    0   0.0      0       0

Percentage of the requests served within a certain time (ms)
  50%      0
  66%      0
  75%      0
  80%      0
  90%      0
  95%      0
  98%      0
  99%      0
 100%      0 (longest request)