From https://once.com/writebook

test/models/leaf_test.rb

@@ -0,0 +1,13 @@
+require "test_helper"
+
+class LeafTest < ActiveSupport::TestCase
+  test "slug is generated from title" do
+    leaf = Leaf.new(title: "Hello, World!")
+    assert_equal "hello-world", leaf.slug
+  end
+
+  test "slug is never completely blank" do
+    leaf = Leaf.new(title: "")
+    assert_equal "-", leaf.slug
+  end
+end