Fix deprecation warning from ActiveSupport for Kernel#capture

test/foreigner/adapter_test.rb

@@ -1,6 +1,6 @@
 require 'helper'
 
-class Foreigner::AdapterTest < ActiveSupport::TestCase
+class Foreigner::AdapterTest < Foreigner::UnitTest
   test "load" do
     Foreigner::Adapter.register 'foo', 'bar'
     Foreigner::Adapter.expects(:configured_name).at_least_once.returns('foo')
@@ -17,13 +17,4 @@ class Foreigner::AdapterTest < ActiveSupport::TestCase
 
     assert_equal 2, output.string.split("\n").length
   end
-
-  private
-  def with_stdout(stream)
-    oldstdout = $stdout
-    $stdout = stream
-    yield
-  ensure
-    $stdout = oldstdout
-  end
 end

test/foreigner/connection_adapters/mysql_adapter_test.rb

@@ -2,10 +2,10 @@
 
 class Foreigner::MysqlAdapterTest < Foreigner::UnitTest
   test 'warning' do
-    skip unless respond_to?(:capture) # < not available until 3.1.x
-    output = capture(:stdout) do
+    output = StringIO.new
+    with_stdout(output) do
       require 'foreigner/connection_adapters/mysql_adapter'
     end
-    assert_match /WARNING: Please upgrade to mysql2. The old mysql adapter is not supported by foreigner./, output
+    assert_match /WARNING: Please upgrade to mysql2. The old mysql adapter is not supported by foreigner./, output.string
   end
 end

test/helper.rb

@@ -48,6 +48,14 @@ def execute(sql, name = nil)
 
 module Foreigner
   class UnitTest < ActiveSupport::TestCase
+    private
+    def with_stdout(stream)
+      oldstdout = $stdout
+      $stdout = stream
+      yield
+    ensure
+      $stdout = oldstdout
+    end
   end
 
   class IntegrationTest < ActiveSupport::TestCase