Manage sandbox test resources in setup/teardown

Library/Homebrew/test/test_sandbox.rb

@@ -4,25 +4,25 @@ require "sandbox"
 class SandboxTest < Homebrew::TestCase
   def setup
     skip "sandbox not implemented" unless Sandbox.available?
+    @sandbox = Sandbox.new
+    @dir = Pathname.new(Dir.mktmpdir)
+    @file = @dir/"foo"
+  end
+
+  def teardown
+    @dir.rmtree
   end
 
   def test_allow_write
-    s = Sandbox.new
-    testpath = Pathname.new(TEST_TMPDIR)
-    foo = testpath/"foo"
-    s.allow_write foo
-    s.exec "touch", foo
-    assert_predicate foo, :exist?
-    foo.unlink
+    @sandbox.allow_write @file
+    @sandbox.exec "touch", @file
+    assert_predicate @file, :exist?
   end
 
   def test_deny_write
-    s = Sandbox.new
-    testpath = Pathname.new(TEST_TMPDIR)
-    bar = testpath/"bar"
     shutup do
-      assert_raises(ErrorDuringExecution) { s.exec "touch", bar }
+      assert_raises(ErrorDuringExecution) { @sandbox.exec "touch", @file }
     end
-    refute_predicate bar, :exist?
+    refute_predicate @file, :exist?
   end
 end