audit (strict): check a test is present.

Library/Homebrew/cmd/audit.rb

@@ -56,6 +56,10 @@ class FormulaText
   def has_trailing_newline?
     /\Z\n/ =~ @text
   end
+
+  def has_test?
+    @text.include? "test do"
+  end
 end
 
 class FormulaAuditor
@@ -104,6 +108,12 @@ class FormulaAuditor
     unless text.has_trailing_newline?
       problem "File should end with a newline"
     end
+
+    if @strict
+      unless text.has_test?
+        problem "A `test do` test block should be added"
+      end
+    end
   end
 
   @@aliases ||= Formula.aliases