Update test

test/custom_importer_test.rb

@@ -3,7 +3,7 @@
 require_relative 'test_helper'
 
 module SassC
-  class CustomImporterTest < MiniTest::Test
+  class CustomImporterTest < Minitest::Test
     include TempFileTest
 
     class CustomImporter < Importer

test/engine_test.rb

@@ -3,7 +3,7 @@
 require_relative 'test_helper'
 
 module SassC
-  class EngineTest < MiniTest::Test
+  class EngineTest < Minitest::Test
     include TempFileTest
 
     def render(data)

test/error_test.rb

@@ -3,7 +3,7 @@
 require_relative 'test_helper'
 
 module SassC
-  class ErrorTest < MiniTest::Test
+  class ErrorTest < Minitest::Test
     def render(data, opts = {})
       Engine.new(data, opts).render
     end

test/functions_test.rb

@@ -4,7 +4,7 @@
 require 'stringio'
 
 module SassC
-  class FunctionsTest < MiniTest::Test
+  class FunctionsTest < Minitest::Test
     include FixtureHelper
 
     def setup

test/output_style_test.rb

@@ -3,7 +3,7 @@
 require_relative 'test_helper'
 
 module SassC
-  class OutputStyleTest < MiniTest::Test
+  class OutputStyleTest < Minitest::Test
     def input_scss
       <<~CSS
         $color: #fff;

test/vendor_test.rb

@@ -3,7 +3,7 @@
 require_relative 'test_helper'
 
 module SassC
-  class VendorTest < MiniTest::Test
+  class VendorTest < Minitest::Test
     class PassthroughImporter < Importer
       def imports(path, _parent_path)
         Import.new(path)