Add Use Tap For Better Test Data Setup as a ruby til

ruby/use-tap-for-better-test-data-setup.md

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+# Use Tap For Better Test Data Setup
+
+I often use RSpec's `let` statement to set up some test data.
+
+```ruby
+let(:order) { create(:order, name: "My Order") }
+```
+
+Often times, realistic test data requires setting up peripheral data as well.
+
+```ruby
+let(:order) do
+  order = create(:order, name: "My Order")
+  create(:item, name: "Burger", order: order, price: 4.99)
+  create(:item, name: "Fries", order: order, price: 2.99)
+  order
+end
+```
+
+This can get hard to read as the subject of the `let` gets obscured. It is also
+clumsy that we have to end with returning the `order`. This can be cleaned up
+with the use of [`#tap`](https://devdocs.io/ruby~2.5/object#method-i-tap).
+
+```ruby
+let(:order) do
+  create(:order, name: "My Order").tap do |order|
+    create(:item, name: "Burger", order: order, price: 4.99)
+    create(:item, name: "Fries", order: order, price: 2.99)
+  end
+end
+```
+
+The block notation and indentation make it clear that the `order` is what is
+getting created. Meanwhile, the interior of the block gives us a designated
+area to do what we need to with the newly-created `order` instance.