Speed up integration tests

The integration tests can be quite slow to run. This is because we are
actually creating a test program as a string, dumping that string into a
temporary file, shelling out to another instance of Ruby/RSpec, running
the file inside of that process, then performing a test on the output.
We have a lot of integration tests, and running the test suite on Travis
can take around 20 minutes. In my opinion, that's way too long for a gem
that isn't terribly large.

This commit attempts to alleviate this pain point by introducing a
development dependency on Zeus. [Zeus] is a "code preloader" that was
primarily designed to speed up development within a Rails app, as it can
preload your Rails environment so that your tests will run faster. While
Zeus has largely been superceded by Spring, it is still a valuable tool
and can also be used for non-Rails applications.

How does Zeus work? The Zeus server is a persistent process that
establishes an environment by running Ruby code of your choosing, then
awaits a connection from the Zeus client, which will then run some code
within that environment. Zeus employs forking to keep the environment
code in memory so that it does not need to be re-run. (This is not the
best description, but there is more information on the website if you
want to learn more.)

The way that we use Zeus is that we create an environment where
`super_diff` is already required and — for tests that need ActiveRecord
— where ActiveRecord is already required too. The integration tests will
then re-use this environment (the code that's run in this environment is
specified in the test itself).

After all is said and done, this ends up speeding up all integration
tests by a little over 2x.

How do you get this goodness? I've added a `bin/start-dev` script which
will run the persistent Zeus server by way of `zeus start`. You will
want to run this command in a separate tab. After this, you can then run
`bin/rspec spec/integration/...` and you should see the speed bump.

[Zeus]: https://github.com/burke/zeus

Author: mcmire

.gitignore

@@ -3,3 +3,5 @@ Gemfile.lock
 pkg
 spec/examples.txt
 tmp
+zeus.server.log
+zeus.server-start.log

.rubocop.yml

@@ -3,7 +3,7 @@ AllCops:
   Exclude:
     - db/schema.rb
   TargetRubyVersion: 2.4
-Layout/AlignParameters:
+Layout/ParameterAlignment:
   EnforcedStyle: with_fixed_indentation
 Layout/ClassStructure:
   Enabled: true
@@ -13,11 +13,11 @@ Layout/CommentIndentation:
   Enabled: false
 Layout/InitialIndentation:
   Enabled: false
-Layout/IndentFirstArrayElement:
+Layout/FirstArrayElementIndentation:
   EnforcedStyle: "consistent"
-Layout/IndentFirstHashElement:
+Layout/FirstHashElementIndentation:
   EnforcedStyle: "consistent"
-Layout/IndentHeredoc:
+Layout/HeredocIndentation:
   Enabled: false
 Layout/MultilineOperationIndentation:
   EnforcedStyle: indented
@@ -29,7 +29,7 @@ Layout/SpaceInsideStringInterpolation:
   Enabled: false
 Lint/AssignmentInCondition:
   Enabled: false
-Lint/HandleExceptions:
+Lint/SuppressedException:
   Enabled: false
 Lint/RequireParentheses:
   Enabled: false
@@ -56,7 +56,7 @@ Metrics/ClassLength:
   Enabled: false
 Metrics/CyclomaticComplexity:
   Max: 15
-Metrics/LineLength:
+Layout/LineLength:
   Max: 80
   IgnoredPatterns:
     - "^\\s*RSpec.describe"
@@ -77,11 +77,11 @@ Naming/AccessorMethodName:
 Naming/MemoizedInstanceVariableName:
   EnforcedStyleForLeadingUnderscores: required
 Naming/PredicateName:
-  NamePrefixBlacklist:
+  ForbiddenPrefixes:
     - is_
   Exclude:
     - spec/**/*
-Naming/UncommunicativeMethodParamName:
+Naming/MethodParameterName:
   Enabled: false
 Style/AccessModifierDeclarations:
   Enabled: false
@@ -91,6 +91,8 @@ Style/CollectionMethods:
   Enabled: true
 Style/Documentation:
   Enabled: false
+Style/DoubleNegation:
+  Enabled: false
 Style/EachWithObject:
   Enabled: false
 Style/EmptyElse:
@@ -99,6 +101,8 @@ Style/EmptyMethod:
   EnforcedStyle: expanded
 Style/FormatString:
   EnforcedStyle: percent
+Style/FormatStringToken:
+  Enabled: false
 Style/FrozenStringLiteralComment:
   Enabled: false
 Style/GuardClause:
@@ -153,7 +157,7 @@ Style/TrailingCommaInArrayLiteral:
   EnforcedStyleForMultiline: comma
 Style/TrailingCommaInHashLiteral:
   EnforcedStyleForMultiline: comma
-Style/UnneededCondition:
+Style/RedundantCondition:
   Enabled: false
 Style/WhileUntilModifier:
   Enabled: false

.travis.yml

@@ -1,6 +1,12 @@
 language: ruby
 before_install:
   - "gem install bundler -v '~> 2.0'"
+  - "gem install zeus"
+  - "bundle config set deployment true"
+  - "unset RAILS_ENV"
+install: "bundle install --jobs=3 --retry=3 --path=${BUNDLE_PATH:-vendor/bundle}"
+before_script:
+  - "bin/start-dev --background --debug"
 cache:
   bundler: true
 env:

CONTRIBUTING.md

@@ -36,6 +36,26 @@ I may have suggestions about code style or your approach,
 but hopefully everything looks good and your changes get merged!
 Now you're a contributor! 🎉
 
+## Speeding up the integration tests
+
+The integration tests,
+located in `spec/integration`,
+can be quite slow to run.
+If you'd like to speed them up,
+run the following command in a separate tab:
+
+```
+zeus start
+```
+
+Now the next time you run an integration test by saying
+
+```
+bin/rspec spec/integration/...
+```
+
+it should run twice as fast.
+
 ## Understanding the codebase
 
 If you want to make a change

Gemfile

@@ -9,10 +9,7 @@ gem "childprocess"
 gem "pry-byebug", platform: :mri
 gem "pry-nav", platform: :jruby
 gem "rake"
-gem "rspec-core", github: "rspec/rspec-core"
-gem "rspec-expectations", github: "rspec/rspec-expectations"
-gem "rspec-mocks", github: "rspec/rspec-mocks"
-gem "rspec-support", github: "rspec/rspec-support"
+gem "rspec"
 gem "rubocop"
 
 gemspec

bin/rspec

@@ -4,6 +4,6 @@ require_relative "../support/current_bundle"
 
 current_bundle = SuperDiff::CurrentBundle.instance
 
-ENV["BUNDLE_GEMFILE"] ||= current_bundle.latest_appraisal.gemfile_path
+ENV["BUNDLE_GEMFILE"] ||= current_bundle.latest_appraisal.gemfile_path.to_s
 
 exec("bundle", "exec", "rspec", *ARGV)

bin/start-dev

@@ -0,0 +1,79 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+success() {
+  echo -e "\033[32m$@\033[0m"
+}
+
+error() {
+  echo -e "\033[31m$@\033[0m"
+}
+
+print-help() {
+  echo "USAGE: $0 [--debug]"
+  echo "This script runs Zeus, for speeding up integration tests."
+}
+
+debug=0
+background=0
+
+while [[ ${1:-} ]]; do
+  case "$1" in
+  --debug)
+    debug=1
+    shift
+    ;;
+  -h | --help)
+    print-help
+    exit
+    ;;
+  --background)
+    background=1
+    shift
+    ;;
+  *)
+    error "Invalid option $1."
+    print-help
+    exit 1
+    ;;
+  esac
+done
+
+if [[ -S .zeus.sock ]]; then
+  error "It looks like Zeus is already running."
+  echo "Try running 'pkill zeus' to stop it, then run this again."
+  exit 1
+fi
+
+if [[ $background -eq 1 ]]; then
+  echo -n "Starting Zeus..."
+
+  if [[ $debug -eq 1 ]]; then
+    rm -f zeus.server.log
+    zeus --log zeus.server.log start &>zeus.server-start.log &
+  else
+    zeus start &>zeus.server-start.log &
+  fi
+  pid="$!"
+  echo " ($pid)"
+
+  echo "Confirming that Zeus is started..."
+
+  sleep 3
+
+  if [[ $debug -eq 1 ]]; then
+    cat zeus.server-start.log
+    if [[ -f zeus.server.log ]]; then
+      cat zeus.server.log
+    fi
+  fi
+
+  exec zeus confirm_started
+else
+  if [[ $debug -eq 1 ]]; then
+    exec zeus --log zeus.server.log start
+  else
+    exec zeus start
+  fi
+fi

config/zeus_plan.rb

@@ -0,0 +1,29 @@
+require "zeus"
+require "zeus/plan"
+require "forwardable"
+
+require_relative "../support/test_plan"
+
+class CustomZeusPlan < Zeus::Plan
+  extend Forwardable
+
+  def_delegators(
+    :@test_plan,
+    :after_fork,
+    :boot,
+    :boot_active_record,
+    :run_plain_test,
+    :run_rspec_active_record_test,
+    :run_rspec_rails_test,
+    :confirm_started,
+  )
+
+  def initialize(using_outside_of_zeus: false, color_enabled: false)
+    @test_plan = TestPlan.new(
+      using_outside_of_zeus: using_outside_of_zeus,
+      color_enabled: color_enabled,
+    )
+  end
+end
+
+Zeus.plan = CustomZeusPlan.new

gemfiles/no_rails.gemfile

@@ -7,10 +7,7 @@ gem "childprocess"
 gem "pry-byebug", platform: :mri
 gem "pry-nav", platform: :jruby
 gem "rake"
-gem "rspec-core", git: "https://github.com/rspec/rspec-core"
-gem "rspec-expectations", git: "https://github.com/rspec/rspec-expectations"
-gem "rspec-mocks", git: "https://github.com/rspec/rspec-mocks"
-gem "rspec-support", git: "https://github.com/rspec/rspec-support"
+gem "rspec"
 gem "rubocop"
 
 gemspec path: "../"

gemfiles/no_rails.gemfile.lock

@@ -1,32 +1,3 @@
-GIT
-  remote: https://github.com/rspec/rspec-core
-  revision: 1174cc5e58ae72fb8cdc689a785089889bfdb740
-  specs:
-    rspec-core (3.10.0.pre)
-      rspec-support (= 3.10.0.pre)
-
-GIT
-  remote: https://github.com/rspec/rspec-expectations
-  revision: c085c5a6f0678ae7f88a489996e391e6b661d8a9
-  specs:
-    rspec-expectations (3.10.0.pre)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (= 3.10.0.pre)
-
-GIT
-  remote: https://github.com/rspec/rspec-mocks
-  revision: e6057a61d8a15c4638dec116f68579d83fdd5ad5
-  specs:
-    rspec-mocks (3.10.0.pre)
-      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (= 3.10.0.pre)
-
-GIT
-  remote: https://github.com/rspec/rspec-support
-  revision: b83b4cecb3bb56300addae89cb0c437f1af906fb
-  specs:
-    rspec-support (3.10.0.pre)
-
 PATH
   remote: ..
   specs:
@@ -43,37 +14,50 @@ GEM
       rake
       thor (>= 0.14.0)
     ast (2.4.0)
-    attr_extras (6.2.2)
-    byebug (11.0.1)
+    attr_extras (6.2.3)
+    byebug (11.1.3)
     childprocess (3.0.0)
     coderay (1.1.2)
     diff-lcs (1.3)
-    jaro_winkler (1.5.4)
-    method_source (0.9.2)
+    method_source (1.0.0)
     parallel (1.19.1)
-    parser (2.7.0.2)
+    parser (2.7.1.2)
       ast (~> 2.4.0)
     patience_diff (1.1.0)
       trollop (~> 1.16)
-    pry (0.12.2)
-      coderay (~> 1.1.0)
-      method_source (~> 0.9.0)
-    pry-byebug (3.7.0)
+    pry (0.13.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
+    pry-byebug (3.9.0)
       byebug (~> 11.0)
-      pry (~> 0.10)
+      pry (~> 0.13.0)
     rainbow (3.0.0)
     rake (13.0.1)
-    rubocop (0.79.0)
-      jaro_winkler (~> 1.5.1)
+    rexml (3.2.4)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.2)
+      rspec-support (~> 3.9.3)
+    rspec-expectations (3.9.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.9.0)
+    rspec-support (3.9.3)
+    rubocop (0.83.0)
       parallel (~> 1.10)
       parser (>= 2.7.0.1)
       rainbow (>= 2.2.2, < 4.0)
+      rexml
       ruby-progressbar (~> 1.7)
-      unicode-display_width (>= 1.4.0, < 1.7)
+      unicode-display_width (>= 1.4.0, < 2.0)
     ruby-progressbar (1.10.1)
     thor (1.0.1)
     trollop (1.16.2)
-    unicode-display_width (1.6.0)
+    unicode-display_width (1.7.0)
 
 PLATFORMS
   ruby
@@ -84,15 +68,9 @@ DEPENDENCIES
   pry-byebug
   pry-nav
   rake
-  rspec-core!
-  rspec-expectations!
-  rspec-mocks!
-  rspec-support!
+  rspec
   rubocop
   super_diff!
 
-RUBY VERSION
-   ruby 2.7.1p83
-
 BUNDLED WITH
    2.1.4