Add Rerun Only Failures With RSpec as a ruby til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_498 TILs and counting..._
+_499 TILs and counting..._
 
 ---
 
@@ -379,6 +379,7 @@ _498 TILs and counting..._
 - [Rendering ERB](ruby/rendering-erb.md)
 - [Replace The Current Process With An External Command](ruby/replace-the-current-process-with-an-external-command.md)
 - [Require Entire Gemfile In Pry Session](ruby/require-entire-gemfile-in-pry-session.md)
+- [Rerun Only Failures With RSpec](ruby/rerun-only-failures-with-rspec.md)
 - [Returning With Sequel](ruby/returning-with-sequel.md)
 - [Running A Single MiniTest Example](ruby/running-a-single-minitest-example.md)
 - [Safe Navigation Operator](ruby/safe-navigation-operator.md)

ruby/rerun-only-failures-with-rspec.md

@@ -0,0 +1,26 @@
+# Rerun Only Failures With RSpec
+
+After running a big test suite, I may have a bunch of output on the screen
+including the results of a couple test failures. I like to bring the context
+of the test failures front and center and make sure they are consistent test
+failures (not flickering failures). Instead of copying and pasting each
+failure, I can rerun `rspec` in a way that executes on the test cases that
+failed.
+
+```
+$ rspec --only-failures
+```
+
+This feature requires that you set a file for RSpec to persist some state
+between runs. Do this in the `spec/spec_helper.rb` file. For example:
+
+```ruby
+RSpec.configure do |config|
+  config.example_status_persistence_file_path = "spec/examples.txt"
+end
+```
+
+See more details
+[here](https://relishapp.com/rspec/rspec-core/docs/command-line/only-failures).
+
+h/t Brian Dunn