1 files changed, 21 insertions, 2 deletions
diff --git a/Library/Homebrew/formula_assertions.rb b/Library/Homebrew/formula_assertions.rb
index a82b06f81..ea12ce001 100644
--- a/Library/Homebrew/formula_assertions.rb
+++ b/Library/Homebrew/formula_assertions.rb
@@ -1,7 +1,26 @@
-require 'test/unit/assertions'
-
 module Homebrew
   module Assertions
+    if defined?(Gem)
+      begin
+        gem "minitest", "< 5.0.0"
+      rescue Gem::LoadError
+        require "test/unit/assertions"
+      else
+        require "minitest/unit"
+        require "test/unit/assertions"
+      end
+    else
+      require "test/unit/assertions"
+    end
+
+    if defined?(MiniTest::Assertion)
+      FailedAssertion = MiniTest::Assertion
+    elsif defined?(Minitest::Assertion)
+      FailedAssertion = Minitest::Assertion
+    else
+      FailedAssertion = Test::Unit::AssertionFailedError
+    end
+
     include Test::Unit::Assertions
 
     # Returns the output of running cmd, and asserts the exit status