From 3a52fbbe9ddd913dac44dcab8811e0baa395a734 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Sat, 13 Apr 2019 09:16:06 -0500
Subject: [PATCH] Add Define A Custom RSpec Matcher as a ruby til

---
 README.md                             |  3 ++-
 ruby/define-a-custom-rspec-matcher.md | 32 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 ruby/define-a-custom-rspec-matcher.md

diff --git a/README.md b/README.md
index f2f4d38..de2bd0c 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_804 TILs and counting..._
+_805 TILs and counting..._
 
 ---
 
@@ -615,6 +615,7 @@ _804 TILs and counting..._
 - [Create Listing Of All Middleman Pages](ruby/create-listing-of-all-middleman-pages.md)
 - [Create Thumbnail Image For A PDF](ruby/create-thumbnail-image-for-a-pdf.md)
 - [Defaulting To Frozen String Literals](ruby/defaulting-to-frozen-string-literals.md)
+- [Define A Custom RSpec Matcher](ruby/define-a-custom-rspec-matcher.md)
 - [Destructuring Arrays In Blocks](ruby/destructuring-arrays-in-blocks.md)
 - [Disassemble Some Codes](ruby/disassemble-some-codes.md)
 - [Double Splat To Merge Hashes](ruby/double-splat-to-merge-hashes.md)
diff --git a/ruby/define-a-custom-rspec-matcher.md b/ruby/define-a-custom-rspec-matcher.md
new file mode 100644
index 0000000..6b5ad97
--- /dev/null
+++ b/ruby/define-a-custom-rspec-matcher.md
@@ -0,0 +1,32 @@
+# Define A Custom RSpec Matcher
+
+You can define your own custom RSpec matchers. This is a great way to keep
+your spec tight and readable. A custom, domain-specific matcher can convey
+more intent in a single line than several lines of built-in matchers.
+
+Here is a matcher to check if something is in a range:
+
+```ruby
+require 'rspec/expectations'
+
+RSpec::Matchers.define :be_betwen do |lower, upper|
+  match do |operand|
+    expect(operand).to be >= lower
+    expect(operand).to be <= upper
+  end
+end
+
+describe MyThing do
+  it "has a value between 0 and 10" do
+    thing = MyThing.new
+
+    expect(thing.value).to be_between(0, 10)
+  end
+end
+```
+
+By requiring `rspec/expectations` we are able to define a matcher that takes
+0 or more arguments (in our case, `lower` and `upper`) and then make
+assertions with them and the `expect` value.
+
+[source](https://relishapp.com/rspec/rspec-expectations/v/2-4/docs/custom-matchers/define-matcher)