Code: create Block class and tests

.bundle/config

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+---
+BUNDLE_BIN: "bin"

.rspec

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+--require spec_helper

Gemfile

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+source "https://rubygems.org"
+
+gem 'rspec'

Gemfile.lock

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+GEM
+  remote: https://rubygems.org/
+  specs:
+    diff-lcs (1.5.0)
+    rspec (3.11.0)
+      rspec-core (~> 3.11.0)
+      rspec-expectations (~> 3.11.0)
+      rspec-mocks (~> 3.11.0)
+    rspec-core (3.11.0)
+      rspec-support (~> 3.11.0)
+    rspec-expectations (3.11.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-mocks (3.11.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.11.0)
+    rspec-support (3.11.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  rspec
+
+BUNDLED WITH
+   2.3.8

bin/bundle

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+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'bundle' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "rubygems"
+
+m = Module.new do
+  module_function
+
+  def invoked_as_script?
+    File.expand_path($0) == File.expand_path(__FILE__)
+  end
+
+  def env_var_version
+    ENV["BUNDLER_VERSION"]
+  end
+
+  def cli_arg_version
+    return unless invoked_as_script? # don't want to hijack other binstubs
+    return unless "update".start_with?(ARGV.first || " ") # must be running `bundle update`
+    bundler_version = nil
+    update_index = nil
+    ARGV.each_with_index do |a, i|
+      if update_index && update_index.succ == i && a =~ Gem::Version::ANCHORED_VERSION_PATTERN
+        bundler_version = a
+      end
+      next unless a =~ /\A--bundler(?:[= ](#{Gem::Version::VERSION_PATTERN}))?\z/
+      bundler_version = $1
+      update_index = i
+    end
+    bundler_version
+  end
+
+  def gemfile
+    gemfile = ENV["BUNDLE_GEMFILE"]
+    return gemfile if gemfile && !gemfile.empty?
+
+    File.expand_path("../../Gemfile", __FILE__)
+  end
+
+  def lockfile
+    lockfile =
+      case File.basename(gemfile)
+      when "gems.rb" then gemfile.sub(/\.rb$/, gemfile)
+      else "#{gemfile}.lock"
+      end
+    File.expand_path(lockfile)
+  end
+
+  def lockfile_version
+    return unless File.file?(lockfile)
+    lockfile_contents = File.read(lockfile)
+    return unless lockfile_contents =~ /\n\nBUNDLED WITH\n\s{2,}(#{Gem::Version::VERSION_PATTERN})\n/
+    Regexp.last_match(1)
+  end
+
+  def bundler_requirement
+    @bundler_requirement ||=
+      env_var_version || cli_arg_version ||
+        bundler_requirement_for(lockfile_version)
+  end
+
+  def bundler_requirement_for(version)
+    return "#{Gem::Requirement.default}.a" unless version
+
+    bundler_gem_version = Gem::Version.new(version)
+
+    requirement = bundler_gem_version.approximate_recommendation
+
+    return requirement unless Gem.rubygems_version < Gem::Version.new("2.7.0")
+
+    requirement += ".a" if bundler_gem_version.prerelease?
+
+    requirement
+  end
+
+  def load_bundler!
+    ENV["BUNDLE_GEMFILE"] ||= gemfile
+
+    activate_bundler
+  end
+
+  def activate_bundler
+    gem_error = activation_error_handling do
+      gem "bundler", bundler_requirement
+    end
+    return if gem_error.nil?
+    require_error = activation_error_handling do
+      require "bundler/version"
+    end
+    return if require_error.nil? && Gem::Requirement.new(bundler_requirement).satisfied_by?(Gem::Version.new(Bundler::VERSION))
+    warn "Activating bundler (#{bundler_requirement}) failed:\n#{gem_error.message}\n\nTo install the version of bundler this project requires, run `gem install bundler -v '#{bundler_requirement}'`"
+    exit 42
+  end
+
+  def activation_error_handling
+    yield
+    nil
+  rescue StandardError, LoadError => e
+    e
+  end
+end
+
+m.load_bundler!
+
+if m.invoked_as_script?
+  load Gem.bin_path("bundler", "bundle")
+end

bin/htmldiff

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+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'htmldiff' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("diff-lcs", "htmldiff")

bin/ldiff

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+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'ldiff' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("diff-lcs", "ldiff")

bin/rspec

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+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rspec' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+require "pathname"
+ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
+  Pathname.new(__FILE__).realpath)
+
+bundle_binstub = File.expand_path("../bundle", __FILE__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require "rubygems"
+require "bundler/setup"
+
+load Gem.bin_path("rspec-core", "rspec")

lib/block.rb

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+require 'digest'
+
+class Block
+  attr_reader :hash
+
+  def initialize(index, data, timestamp= Time.now.inspect, previous_hash='')
+    @index = index
+    @data = data
+    @timestamp = timestamp
+    @previous_hash = previous_hash
+    @hash = calculate_hash
+  end
+
+  private
+
+  def calculate_hash
+    Digest::SHA256.hexdigest @index.to_s + @data.to_s + @timestamp.to_s + @previous_hash.to_s
+  end
+end

spec/block_spec.rb

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+require 'block'
+
+RSpec.describe Block, '#initialize' do
+    let(:new_block) { Block.new(1,{data: "some data"}) }
+    it "creates a new Block instance" do
+        expected = new_block
+
+        expect(expected).to be_an_instance_of Block
+    end
+    it "generate a unique hash for the block" do
+        expected = new_block.hash
+        another_block = Block.new(2,{data: "another data"})
+
+        expect(expected.length).to eq 64
+        expect(expected).to be_an_instance_of String
+        expect(expected).to_not eq another_block.hash
+    end
+end

spec/spec_helper.rb

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+# This file was generated by the `rspec --init` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+# The settings below are suggested to provide a good initial experience
+# with RSpec, but feel free to customize to your heart's content.
+=begin
+  # This allows you to limit a spec run to individual examples or groups
+  # you care about by tagging them with `:focus` metadata. When nothing
+  # is tagged with `:focus`, all examples get run. RSpec also provides
+  # aliases for `it`, `describe`, and `context` that include `:focus`
+  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  config.filter_run_when_matching :focus
+
+  # Allows RSpec to persist some state between runs in order to support
+  # the `--only-failures` and `--next-failure` CLI options. We recommend
+  # you configure your source control system to ignore this file.
+  config.example_status_persistence_file_path = "spec/examples.txt"
+
+  # Limits the available syntax to the non-monkey patched syntax that is
+  # recommended. For more details, see:
+  # https://relishapp.com/rspec/rspec-core/docs/configuration/zero-monkey-patching-mode
+  config.disable_monkey_patching!
+
+  # This setting enables warnings. It's recommended, but in some cases may
+  # be too noisy due to issues in dependencies.
+  config.warnings = true
+
+  # Many RSpec users commonly either run the entire suite or an individual
+  # file, and it's useful to allow more verbose output when running an
+  # individual spec file.
+  if config.files_to_run.one?
+    # Use the documentation formatter for detailed output,
+    # unless a formatter has already been configured
+    # (e.g. via a command-line flag).
+    config.default_formatter = "doc"
+  end
+
+  # Print the 10 slowest examples and example groups at the
+  # end of the spec run, to help surface which specs are running
+  # particularly slow.
+  config.profile_examples = 10
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = :random
+
+  # Seed global randomization in this process using the `--seed` CLI option.
+  # Setting this allows you to use `--seed` to deterministically reproduce
+  # test failures related to randomization by passing the same `--seed` value
+  # as the one that triggered the failure.
+  Kernel.srand config.seed
+=end
+end