Better support test-unit or minitest

Gemfile.lock

@@ -8,6 +8,7 @@ GEM
   specs:
     builder (3.2.2)
     diff-lcs (1.2.5)
+    minitest (5.4.3)
     pr_geohash (1.0.0)
     rake (10.4.2)
     rsolr (1.0.12)
@@ -34,6 +35,7 @@ PLATFORMS
 
 DEPENDENCIES
   bundler (>= 1.0.0)
+  minitest
   rake
   rspec
   sunspot (~> 2.2.0)

lib/sunspot_matchers/sunspot_session_spy.rb

@@ -24,6 +24,7 @@ def initialize(original_session)
       # Support Sunspot random field in test -- Sunspot originally generate a random number for the field
       # Only patch method if SunspotSessionSpy is initialized to prevent poisoning class simply by being included in Gemfile.
       Sunspot::Query::Sort::RandomSort.class_eval do
+        remove_method :to_param
         define_method :to_param do
           "random #{direction_for_solr}"
         end

lib/sunspot_matchers/test_helper.rb

@@ -1,10 +1,13 @@
 require 'sunspot'
-require 'minitest/autorun'
 require File.expand_path('../matchers', __FILE__)
 require File.expand_path('../sunspot_session_spy', __FILE__)
 module SunspotMatchers
   class HaveSearchParamsForSession
-    include MiniTest::Assertions
+    if defined?(MiniTest::Assertions)
+      include MiniTest::Assertions
+    else
+      include Test::Unit::Assertions
+    end
 
     def initialize(session, method, *args, &block)
       @session = session

sunspot_matchers.gemspec

@@ -18,6 +18,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rspec"
   s.add_development_dependency "sunspot", "~> 2.2.0"
   s.add_development_dependency "rake"
+  s.add_development_dependency "minitest"
 
   s.files        = `git ls-files`.split("\n")
   s.require_path = 'lib'

test/sunspot_matchers_test.rb

@@ -1,5 +1,6 @@
 require 'rubygems'
 require 'bundler'
+require 'minitest/autorun'
 require 'sunspot_matchers/test_helper'
 
 class Post; end
@@ -22,7 +23,7 @@ class Person; end
   string :name
 end
 
-class SunspotMatchersTest < MiniTest::Unit::TestCase
+class SunspotMatchersTest < MiniTest::Test
   include SunspotMatchers::TestHelper
 
   def setup