```ruby
class DeferredGarbageCollection
DEFERRED_GC_THRESHOLD = (ENV['DEFER_GC'] || 10.0).to_f
@last_gc_run = Time.now
def self.start
GC.disable if DEFERRED_GC_THRESHOLD > 0
end
def self.reconsider
if DEFERRED_GC_THRESHOLD > 0 && Time.now - @last_gc_run >= DEFERRED_GC_THRESHOLD
GC.enable
GC.start
GC.disable
@last_gc_run = Time.now
end
end
end
module MiniTestDeferredGC
def before_setup
DeferredGarbageCollection.start
super
end
def after_teardown
super
DeferredGarbageCollection.reconsider
end
end
class MiniTest::Test
include MiniTestDeferredGC
end
```