add helpers for formula tests

Library/Homebrew/cmd/test.rb

@@ -25,6 +25,8 @@ module Homebrew
     FailedAssertion = Test::Unit::AssertionFailedError
   end
 
+  require "formula_assertions"
+
   def test
     raise FormulaUnspecifiedError if ARGV.named.empty?
 
@@ -47,6 +49,7 @@ module Homebrew
       puts "Testing #{f.name}"
 
       f.extend(Test::Unit::Assertions)
+      f.extend(Homebrew::Assertions)
 
       begin
         # tests can also return false to indicate failure

Library/Homebrew/formula_assertions.rb

@@ -0,0 +1,23 @@
+require 'test/unit/assertions'
+
+module Homebrew
+  module Assertions
+    include Test::Unit::Assertions
+
+    # Returns the output of running cmd, and asserts the exit status
+    def shell_output(cmd, result=0)
+      output = `#{cmd}`
+      assert_equal result, $?.exitstatus
+      output
+    end
+
+    # Returns the output of running the cmd, with the optional input
+    def pipe_output(cmd, input=nil)
+      IO.popen(cmd, "w+") do |pipe|
+        pipe.write(input) unless input.nil?
+        pipe.close_write
+        pipe.read
+      end
+    end
+  end
+end