Replace Zeus with process forking strategy (#271)

Integration tests without Zeus are very slow because we run each example
in a new process, which has to load all dependencies and frameworks –
like RSpec, SuperDiff, ActiveSupport, etc – from scratch.

Zeus improved on this, but has a client-server architecture and has been
proving somewhat difficult to use. If we instead load the dependencies
and then run RSpec in a new
[_forked_](https://man7.org/linux/man-pages/man2/fork.2.html)
subprocess, we don't have to reload anything loaded before fork time,
and don't have to use Zeus.

Light testing shows a ~5x speed-up over non-Zeus integration tests.

Author: jas14

.gitignore

@@ -6,8 +6,6 @@ pkg
 spec/examples.txt
 spec/internal
 tmp
-zeus.server.log
-zeus.server-start.log
 
 # Ignore Yarn stuff
 .pnp.*

CHANGELOG.md

@@ -12,6 +12,7 @@
 
 - Switch from Prettier to Rubocop. [#269](https://github.com/splitwise/super_diff/pull/269)
 - Fix outdated reference in documentation. [#270](https://github.com/splitwise/super_diff/pull/270) by [@emmanuel-ferdman](https://github.com/emmanuel-ferdman)
+- Replace Zeus with forking strategy for tests. [#271](https://github.com/splitwise/super_diff/pull/271)
 
 ## 0.13.0 - 2024-09-22
 

Gemfile

@@ -16,6 +16,5 @@ gem 'rubocop'
 gem 'syntax_tree'
 gem 'syntax_tree-haml'
 gem 'syntax_tree-rbs'
-gem 'warnings_logger'
 
 gemspec

Gemfile.lock

@@ -83,7 +83,6 @@ GEM
     thor (1.3.2)
     tilt (2.4.0)
     unicode-display_width (2.6.0)
-    warnings_logger (0.1.1)
 
 PLATFORMS
   arm64-darwin-21
@@ -105,7 +104,6 @@ DEPENDENCIES
   syntax_tree
   syntax_tree-haml
   syntax_tree-rbs
-  warnings_logger
 
 BUNDLED WITH
    2.5.20

bin/start-dev

@@ -244,28 +244,17 @@ They are divided into two kinds:
   holds tests for individual classes and methods.
 - **Integration tests**, located in `spec/integration/`,
   construct tiny test suites which import SuperDiff
-  and run them in isolated environments
+  and run them in forked processes
   to ensure that SuperDiff works as designed
-  in more real-world scenarios.
+  in more real-world scenarios. We fork instead of
+  running from scratch to avoid having to reload
+  SuperDiff and other libraries for every example.
 
 The files in `spec/support/` (imported via `spec_helper.rb`)
 contain helpers, matchers, and tests
 that are shared among unit and integration tests,
 at their respective levels.
 
-Beyond this, [Zeus][zeus], a way to speed up integration tests,
-and is run and configured via these files:
-
-- `bin/start-dev`
-- `config/zeus_plan.rb`
-- `support/test_plan.rb`
-- `zeus.json`
-
-The [official Zeus docs](https://github.com/burke/zeus/blob/master/docs/ruby/modifying.md)
-is helpful for understanding how these files work together.
-
-[zeus]: https://github.com/burke/zeus
-
 ## Ruby
 
 The following files are used to set up Ruby,

docs/contributors/architecture/structure.md

@@ -62,23 +62,6 @@ bin/rspec spec/integration/...
 bin/rspec spec/unit/...
 ```
 
-Note that the integration tests
-can be quite slow to run.
-If you'd like to speed them up,
-run the following command in a separate terminal session:
-
-```
-zeus start
-```
-
-Now the next time you run an integration test by saying
-
-```
-bin/rspec spec/integration/...
-```
-
-it should run twice as fast.
-
 ## 5. Run the linter
 
 Code is linted and formatted using Rubocop.

docs/contributors/how-to-contribute.md

@@ -14,7 +14,6 @@ gem "rubocop"
 gem "syntax_tree"
 gem "syntax_tree-haml"
 gem "syntax_tree-rbs"
-gem "warnings_logger"
 gem "rspec", "3.12.0"
 gem "rspec-core", "3.12.0"
 gem "rspec-expectations", "3.12.3"

gemfiles/no_rails_rspec_gte_3_10.gemfile

@@ -14,7 +14,6 @@ gem "rubocop"
 gem "syntax_tree"
 gem "syntax_tree-haml"
 gem "syntax_tree-rbs"
-gem "warnings_logger"
 gem "rspec", "~> 3.9.0"
 
 gemspec path: "../"

gemfiles/no_rails_rspec_lt_3_10.gemfile

@@ -14,7 +14,6 @@ gem "rubocop"
 gem "syntax_tree"
 gem "syntax_tree-haml"
 gem "syntax_tree-rbs"
-gem "warnings_logger"
 gem "activerecord-jdbcsqlite3-adapter", platform: :jruby
 gem "jdbc-sqlite3", platform: :jruby
 gem "net-ftp"