1 files changed, 28 insertions, 0 deletions
diff --git a/spec/ruby/library/stringscanner/unscan_spec.rb b/spec/ruby/library/stringscanner/unscan_spec.rb
new file mode 100644
index 0000000000..f738778273
--- /dev/null
+++ b/spec/ruby/library/stringscanner/unscan_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#unscan" do
+  before :each do
+    @s = StringScanner.new("This is a test")
+  end
+
+  it "set the scan pointer to the previous position" do
+    @s.scan(/This/)
+    @s.unscan
+    @s.matched.should == nil
+    @s.pos.should == 0
+  end
+
+  it "remember only one previous position" do
+    @s.scan(/This/)
+    pos = @s.pos
+    @s.scan(/ is/)
+    @s.unscan
+    @s.pos.should == pos
+  end
+
+  it "raises a StringScanner::Error when the previous match had failed" do
+    -> { @s.unscan }.should.raise(StringScanner::Error)
+    -> { @s.scan(/\d/); @s.unscan }.should.raise(StringScanner::Error)
+  end
+end