1 files changed, 53 insertions, 7 deletions
diff --git a/spec/ruby/core/thread/backtrace_locations_spec.rb b/spec/ruby/core/thread/backtrace_locations_spec.rb
index 66947f8ea6..28a488f311 100644
--- a/spec/ruby/core/thread/backtrace_locations_spec.rb
+++ b/spec/ruby/core/thread/backtrace_locations_spec.rb
@@ -3,20 +3,66 @@ require_relative '../../spec_helper'
 describe "Thread#backtrace_locations" do
   it "returns an Array" do
     locations = Thread.current.backtrace_locations
-    locations.should be_an_instance_of(Array)
-    locations.should_not be_empty
+    locations.should.instance_of?(Array)
+    locations.should_not.empty?
   end
 
   it "sets each element to a Thread::Backtrace::Location" do
     locations = Thread.current.backtrace_locations
-    locations.each { |loc| loc.should be_an_instance_of(Thread::Backtrace::Location) }
+    locations.each { |loc| loc.should.instance_of?(Thread::Backtrace::Location) }
   end
 
   it "can be called on any Thread" do
     locations = Thread.new { Thread.current.backtrace_locations }.value
-    locations.should be_an_instance_of(Array)
-    locations.should_not be_empty
-    locations.each { |loc| loc.should be_an_instance_of(Thread::Backtrace::Location) }
+    locations.should.instance_of?(Array)
+    locations.should_not.empty?
+    locations.each { |loc| loc.should.instance_of?(Thread::Backtrace::Location) }
+  end
+
+  it "can be called with a number of locations to omit" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2)
+    locations2.length.should == locations1[2..-1].length
+    locations2.map(&:to_s).should == locations1[2..-1].map(&:to_s)
+  end
+
+  it "can be called with a maximum number of locations to return as second parameter" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2, 3)
+    locations2.map(&:to_s).should == locations1[2..4].map(&:to_s)
+  end
+
+  it "can be called with a range" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2..4)
+    locations2.map(&:to_s).should == locations1[2..4].map(&:to_s)
+  end
+
+  it "can be called with a range whose end is negative" do
+    Thread.current.backtrace_locations(2..-1).map(&:to_s).should == Thread.current.backtrace_locations[2..-1].map(&:to_s)
+    Thread.current.backtrace_locations(2..-2).map(&:to_s).should == Thread.current.backtrace_locations[2..-2].map(&:to_s)
+  end
+
+  it "can be called with an endless range" do
+    locations1 = Thread.current.backtrace_locations(0)
+    locations2 = Thread.current.backtrace_locations(eval("(2..)"))
+    locations2.map(&:to_s).should == locations1[2..-1].map(&:to_s)
+  end
+
+  it "can be called with an beginless range" do
+    locations1 = Thread.current.backtrace_locations(0)
+    locations2 = Thread.current.backtrace_locations((..5))
+    locations2.map(&:to_s)[eval("(2..)")].should == locations1[(..5)].map(&:to_s)[eval("(2..)")]
+  end
+
+  it "returns nil if omitting more locations than available" do
+    Thread.current.backtrace_locations(100).should == nil
+    Thread.current.backtrace_locations(100..-1).should == nil
+  end
+
+  it "returns [] if omitting exactly the number of locations available" do
+    omit = Thread.current.backtrace_locations.length
+    Thread.current.backtrace_locations(omit).should == []
   end
 
   it "without argument is the same as showing all locations with 0..-1" do
@@ -24,7 +70,7 @@ describe "Thread#backtrace_locations" do
   end
 
   it "the first location reports the call to #backtrace_locations" do
-    Thread.current.backtrace_locations(0..0)[0].to_s.should == "#{__FILE__ }:#{__LINE__ }:in `backtrace_locations'"
+    Thread.current.backtrace_locations(0..0)[0].to_s.should =~ /\A#{__FILE__ }:#{__LINE__ }:in [`'](?:Thread#)?backtrace_locations'\z/
   end
 
   it "[1..-1] is the same as #caller_locations(0..-1) for Thread.current" do