1 files changed, 37 insertions, 3 deletions
diff --git a/spec/ruby/core/thread/backtrace_spec.rb b/spec/ruby/core/thread/backtrace_spec.rb
index 84ed574d5c..770c300f06 100644
--- a/spec/ruby/core/thread/backtrace_spec.rb
+++ b/spec/ruby/core/thread/backtrace_spec.rb
@@ -12,8 +12,8 @@ describe "Thread#backtrace" do
     Thread.pass while t.status && t.status != 'sleep'
 
     backtrace = t.backtrace
-    backtrace.should be_kind_of(Array)
-    backtrace.first.should =~ /`sleep'/
+    backtrace.should.is_a?(Array)
+    backtrace.first.should =~ /[`'](?:Kernel#)?sleep'/
 
     t.raise 'finish the thread'
     t.join
@@ -30,6 +30,40 @@ describe "Thread#backtrace" do
     backtrace = t.backtrace
     t.kill
     t.join
-    backtrace.should be_kind_of(Array)
+    backtrace.should.is_a?(Array)
+  end
+
+  it "can be called with a number of locations to omit" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2)
+    locations1[2..-1].length.should == locations2.length
+    locations1[2..-1].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a maximum number of locations to return as second parameter" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2, 3)
+    locations1[2..4].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a range" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2..4)
+    locations1[2..4].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a range whose end is negative" do
+    Thread.current.backtrace(2..-1).should == Thread.current.backtrace[2..-1]
+    Thread.current.backtrace(2..-2).should == Thread.current.backtrace[2..-2]
+  end
+
+  it "returns nil if omitting more locations than available" do
+    Thread.current.backtrace(100).should == nil
+    Thread.current.backtrace(100..-1).should == nil
+  end
+
+  it "returns [] if omitting exactly the number of locations available" do
+    omit = Thread.current.backtrace.length
+    Thread.current.backtrace(omit).should == []
   end
 end