Only assert a lower bound on sleep times

* There might be arbitrary delays due to GC, other process, load, etc.

Author: eregon

spec/ruby/core/kernel/sleep_spec.rb

@@ -6,16 +6,20 @@
     Kernel.should have_private_instance_method(:sleep)
   end
 
+  it "returns an Integer" do
+    sleep(0.001).should be_kind_of(Integer)
+  end
+
   it "accepts a Float" do
-    sleep(0.1).should be_close(0, 2)
+    sleep(0.001).should >= 0
   end
 
   it "accepts a Fixnum" do
-    sleep(0).should be_close(0, 2)
+    sleep(0).should >= 0
   end
 
   it "accepts a Rational" do
-    sleep(Rational(1, 9)).should be_close(0, 2)
+    sleep(Rational(1, 999)).should >= 0
   end
 
   it "raises an ArgumentError when passed a negative duration" do

spec/ruby/optional/capi/mutex_spec.rb

@@ -72,9 +72,10 @@
 
     it "sleeps when the mutex is locked" do
       @m.lock
-      start = Time.now
-      @s.rb_mutex_sleep(@m, 0.1)
-      (Time.now - start).should be_close(0.1, 0.2)
+      t1 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      @s.rb_mutex_sleep(@m, 0.001)
+      t2 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (t2 - t1).should >= 0
       @m.locked?.should be_true
     end
   end