[api] remove one left over from test::unit

src/api/test/test_helper.rb

@@ -5,7 +5,7 @@
 
 require File.expand_path('../../config/environment', __FILE__)
 require 'rails/test_help'
-require 'test/unit/assertions'
+require 'minitest/unit'
 
 # uncomment to enable tests which currently are known to fail, but where either the test
 # or the code has to be fixed
@@ -90,13 +90,13 @@ def load_backend_file(path)
     def assert_xml_tag(conds)
       node = ActiveXML::Base.new(@response.body)
       ret = node.find_matching(NodeMatcher::Conditions.new(conds))
-      raise Test::Unit::AssertionFailedError.new("expected tag, but no tag found matching #{conds.inspect} in:\n#{node.dump_xml}") unless ret
+      raise MiniTest::Assertion.new("expected tag, but no tag found matching #{conds.inspect} in:\n#{node.dump_xml}") unless ret
     end
 
     def assert_no_xml_tag(conds)
      node = ActiveXML::Base.new(@response.body)
      ret = node.find_matching(NodeMatcher::Conditions.new(conds))
-     raise Test::Unit::AssertionFailedError.new("expected no tag, but found tag matching #{conds.inspect} in:\n#{node.dump_xml}") if ret
+     raise MiniTest::Assertion.new("expected no tag, but found tag matching #{conds.inspect} in:\n#{node.dump_xml}") if ret
     end
 
     # useful to fix our test cases