Add Fail as a ruby til

README.md

@@ -242,6 +242,7 @@ _336 TILs and counting..._
 - [Editing Code In Pry](ruby/editing-code-in-pry.md)
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
 - [FactoryGirl Sequences](ruby/factory-girl-sequences.md)
+- [Fail](ruby/fail.md)
 - [Finding The Source of Ruby Methods](ruby/finding-the-source-of-ruby-methods.md)
 - [Identify Outdated Gems](ruby/identify-outdated-gems.md)
 - [If You Detect None](ruby/if-you-detect-none.md)

ruby/fail.md

@@ -0,0 +1,22 @@
+# Fail
+
+The `fail` method is synonymous with `raise` in Ruby. Consider the following
+code snippet:
+
+```ruby
+def is_odd?(num)
+  num.odd?
+rescue
+  fail StandardError, 'you cannot use odd on this'
+end
+
+> is_odd?(1)
+#=> true
+> is_odd?('hello')
+#=> StandardError: you cannot use odd on this
+```
+
+Nevertheless, I believe the `raise` method is preferred to the `fail`
+method.
+
+[source](http://ruby-doc.org/core-2.3.0/Kernel.html#method-i-fail)