1 files changed, 17 insertions, 4 deletions
diff --git a/spec/ruby/core/time/shared/now.rb b/spec/ruby/core/time/shared/now.rb
index c35115fcf4..839cfdcd2a 100644
--- a/spec/ruby/core/time/shared/now.rb
+++ b/spec/ruby/core/time/shared/now.rb
@@ -1,14 +1,14 @@
-require File.expand_path('../../fixtures/classes', __FILE__)
+require_relative '../fixtures/classes'
 
 describe :time_now, shared: true do
   it "creates a subclass instance if called on a subclass" do
-    TimeSpecs::SubTime.send(@method).should be_an_instance_of(TimeSpecs::SubTime)
-    TimeSpecs::MethodHolder.send(@method).should be_an_instance_of(Time)
+    TimeSpecs::SubTime.send(@method).should.instance_of?(TimeSpecs::SubTime)
+    TimeSpecs::MethodHolder.send(@method).should.instance_of?(Time)
   end
 
   it "sets the current time" do
     now = TimeSpecs::MethodHolder.send(@method)
-    now.to_f.should be_close(Process.clock_gettime(Process::CLOCK_REALTIME), 10.0)
+    now.to_f.should be_close(Process.clock_gettime(Process::CLOCK_REALTIME), TIME_TOLERANCE)
   end
 
   it "uses the local timezone" do
@@ -17,4 +17,17 @@ describe :time_now, shared: true do
       now.utc_offset.should == (-8 * 60 * 60)
     end
   end
+
+  it "has at least microsecond precision" do
+    # The clock should not be less accurate than expected (times should
+    # not all be a multiple of the next precision up, assuming precisions
+    # are multiples of ten.)
+    expected = 1_000
+    t = 0
+    10_000.times.find do
+      t = Time.now.nsec
+      t % (expected * 10) != 0
+    end
+    (t % (expected * 10)).should != 0
+  end
 end