Document Assertions.

Library/Homebrew/formula_assertions.rb

@@ -1,6 +1,9 @@
 # frozen_string_literal: true
 
 module Homebrew
+  # Helper functions available in formula `test` blocks.
+  #
+  # @api private
   module Assertions
     include Context
 
@@ -8,6 +11,7 @@ module Homebrew
     include ::Test::Unit::Assertions
 
     # Returns the output of running cmd, and asserts the exit status
+    # @api public
     def shell_output(cmd, result = 0)
       ohai cmd
       output = `#{cmd}`
@@ -19,7 +23,8 @@ module Homebrew
     end
 
     # Returns the output of running the cmd with the optional input, and
-    # optionally asserts the exit status
+    # optionally asserts the exit status.
+    # @api public
     def pipe_output(cmd, input = nil, result = nil)
       ohai cmd
       output = IO.popen(cmd, "w+") do |pipe|