Convert to RSpec

7 files changed, 1199 insertions, 0 deletions

diff --git a/spec/diff_lcs_balanced_spec.rb b/spec/diff_lcs_balanced_spec.rb
new file mode 100644
index 0000000..36e11c9
--- /dev/null
+++ b/spec/diff_lcs_balanced_spec.rb
@@ -0,0 +1,169 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.traverse_balanced should traverse sequences correctly" do
+  include Diff::LCS::SpecHelper::Matchers
+
+  def reverse(change_result)
+    new_result = []
+    change_result.each { |line|
+      line = [ line[0], line[2], line[1] ]
+      case line[0]
+      when '<'
+        line[0] = '>'
+      when '>'
+        line[0] = '<'
+      end
+      new_result << line
+    }
+    new_result.sort_by { |line| line[1] }
+  end
+
+  def no_change(change_result)
+    new_result = []
+    change_result.each { |line|
+      case line[0]
+      when '!'
+        new_result << [ '<', line[1], line[2] ]
+        new_result << [ '>', line[1] + 1, line[2] ]
+      else
+        new_result << line
+      end
+    }
+    new_result
+  end
+
+  def traverse(s1, s2, callback_type)
+    callback = __send__(callback_type)
+    Diff::LCS.traverse_balanced(s1, s2, callback)
+    callback
+  end
+
+  def do_balanced_traversal(s1, s2, result)
+    balanced_s1_s2 = traverse(s1, s2, :balanced_callback)
+    balanced_s2_s1 = traverse(s2, s1, :balanced_callback)
+    balanced_s1_s2_no_change = traverse(s1, s2, :balanced_callback_no_change)
+    balanced_s2_s1_no_change = traverse(s2, s1, :balanced_callback_no_change)
+
+    balanced_s1_s2.result.should == result
+    balanced_s2_s1.result.should == reverse(result)
+
+    balanced_s1_s2_no_change.result.should == no_change(result)
+    balanced_s2_s1_no_change.result.should == no_change(reverse(result))
+  end
+
+  it "sequence-a" do
+    s1 = %w(a b c)
+    s2 = %w(a x c)
+
+    result = [
+      [ '=', 0, 0 ],
+      [ '!', 1, 1 ],
+      [ '=', 2, 2 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-b" do
+    s1 = %w(a x y c)
+    s2 = %w(a v w c)
+
+    result = [
+      [ '=', 0, 0 ],
+      [ '!', 1, 1 ],
+      [ '!', 2, 2 ],
+      [ '=', 3, 3 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-c" do
+    s1 = %w(x y c)
+    s2 = %w(v w c)
+    result = [
+      [ '!', 0, 0 ],
+      [ '!', 1, 1 ],
+      [ '=', 2, 2 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-d" do
+    s1 = %w(a x y z)
+    s2 = %w(b v w)
+    result = [
+      [ '!', 0, 0 ],
+      [ '!', 1, 1 ],
+      [ '!', 2, 2 ],
+      [ '<', 3, 3 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-e" do
+    s1 = %w(a z)
+    s2 = %w(a)
+    result = [
+      [ '=', 0, 0 ],
+      [ '<', 1, 1 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-f" do
+    s1 = %w(z a)
+    s2 = %w(a)
+    result = [
+      [ '<', 0, 0 ],
+      [ '=', 1, 0 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-g" do
+    s1 = %w(a b c)
+    s2 = %w(x y z)
+    result = [
+      [ '!', 0, 0 ],
+      [ '!', 1, 1 ],
+      [ '!', 2, 2 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-h" do
+    s1 = %w(abcd efgh ijkl mnopqrstuvwxyz)
+    s2 = []
+    result = [
+      [ '<', 0, 0 ],
+      [ '<', 1, 0 ],
+      [ '<', 2, 0 ],
+      [ '<', 3, 0 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+
+  it "sequence-i" do
+    s1 = []
+    s2 = %w(abcd efgh ijkl mnopqrstuvwxyz)
+    result = [
+      [ '>', 0, 0 ],
+      [ '>', 0, 1 ],
+      [ '>', 0, 2 ],
+      [ '>', 0, 3 ]
+    ]
+
+    do_balanced_traversal(s1, s2, result)
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/diff_lcs_diff_spec.rb b/spec/diff_lcs_diff_spec.rb
new file mode 100644
index 0000000..43ea5c7
--- /dev/null
+++ b/spec/diff_lcs_diff_spec.rb
@@ -0,0 +1,33 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.diff" do
+  include Diff::LCS::SpecHelper::Matchers
+
+  it "should correctly diff the sequences" do
+    diff_s1_s2 = Diff::LCS.diff(seq1, seq2)
+    diff_s2_s1 = Diff::LCS.diff(seq2, seq1)
+
+    change_diff(correct_forward_diff).should == diff_s1_s2
+    change_diff(correct_backward_diff).should == diff_s2_s1
+  end
+
+  it "should correctly diff against an empty sequence" do
+    diff = Diff::LCS.diff(word_sequence, [])
+    correct_diff = [
+      [ [ '-', 0, 'abcd'           ],
+        [ '-', 1, 'efgh'           ],
+        [ '-', 2, 'ijkl'           ],
+        [ '-', 3, 'mnopqrstuvwxyz' ] ]
+    ]
+
+    change_diff(correct_diff).should == diff
+
+    diff = Diff::LCS.diff([], word_sequence)
+    correct_diff.each { |hunk| hunk.each { |change| change[0] = '+' } }
+    change_diff(correct_diff).should == diff
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/diff_lcs_lcs_spec.rb b/spec/diff_lcs_lcs_spec.rb
new file mode 100644
index 0000000..c95ba61
--- /dev/null
+++ b/spec/diff_lcs_lcs_spec.rb
@@ -0,0 +1,36 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.LCS and Diff::LCS.__lcs" do
+  include Diff::LCS::SpecHelper::Matchers
+
+  it "should return the correct raw values from Diff::LCS.__lcs" do
+    res = Diff::LCS.__lcs(seq1, seq2)
+    # The result of the LCS (less the +nil+ values) must be as long as the
+    # correct result.
+    res.compact.size.should == correct_lcs.size
+    res.should correctly_map_sequence(seq1).to_other_sequence(seq2)
+
+    # Compact these transformations and they should be the correct LCS.
+    x_seq1 = (0...res.size).map { |ix| res[ix] ? seq1[ix] : nil }.compact
+    x_seq2 = (0...res.size).map { |ix| res[ix] ? seq2[res[ix]] : nil }.compact
+
+    x_seq1.should == correct_lcs
+    x_seq2.should == correct_lcs
+  end
+
+  it "should return the correct compacted values from Diff::LCS.LCS" do
+    res = Diff::LCS.LCS(seq1, seq2)
+    res.should == correct_lcs
+    res.compact.should == res
+  end
+
+  it "should be transitive" do
+    res = Diff::LCS.LCS(seq2, seq1)
+    res.should == correct_lcs
+    res.compact.should == res
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/diff_lcs_patch_spec.rb b/spec/diff_lcs_patch_spec.rb
new file mode 100644
index 0000000..7e480e0
--- /dev/null
+++ b/spec/diff_lcs_patch_spec.rb
@@ -0,0 +1,428 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.patch" do
+  include Diff::LCS::SpecHelper::Matchers
+
+  describe "using a Diff::LCS.diff patchset" do
+    describe "with default diff callbacks (DiffCallbacks)" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(seq1, seq2)
+        @patch_set_s2_s1 = Diff::LCS.diff(seq2, seq1)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+
+    describe "with context diff callbacks (ContextDiffCallbacks)" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(seq1, seq2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(seq2, seq1, Diff::LCS::ContextDiffCallbacks)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+
+    describe "with sdiff callbacks (SDiffCallbacks)" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(seq1, seq2, Diff::LCS::SDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(seq2, seq1, Diff::LCS::SDiffCallbacks)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+  end
+
+  describe "using a Diff::LCS.sdiff patchset" do
+    describe "with default diff callbacks (DiffCallbacks)" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(seq1, seq2, Diff::LCS::DiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(seq2, seq1, Diff::LCS::DiffCallbacks)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+
+    describe "with context diff callbacks (ContextDiffCallbacks)" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(seq1, seq2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(seq2, seq1, Diff::LCS::ContextDiffCallbacks)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+
+    describe "with sdiff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(seq1, seq2)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(seq2, seq1)
+      end
+
+      it "should correctly patch left-to-right (patch autodiscovery)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(seq1, @patch_set_s1_s2, :patch).should == seq2
+        Diff::LCS.patch(seq2, @patch_set_s2_s1, :patch).should == seq1
+        Diff::LCS.patch!(seq1, @patch_set_s1_s2).should == seq2
+        Diff::LCS.patch!(seq2, @patch_set_s2_s1).should == seq1
+      end
+
+      it "should correctly patch right-to-left (unpatch autodiscovery)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1).should == seq2
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(seq2, @patch_set_s1_s2, :unpatch).should == seq1
+        Diff::LCS.patch(seq1, @patch_set_s2_s1, :unpatch).should == seq2
+        Diff::LCS.unpatch!(seq2, @patch_set_s1_s2).should == seq1
+        Diff::LCS.unpatch!(seq1, @patch_set_s2_s1).should == seq2
+      end
+    end
+  end
+
+  describe "fix bug 891: patchsets do not contain the last equal part" do
+    before(:each) do
+      @s1 = %w(a b c d   e f g h i j k)
+      @s2 = %w(a b c d D e f g h i j k)
+    end
+
+    describe "using Diff::LCS.diff with default diff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2)
+        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+
+    describe "using Diff::LCS.diff with context diff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1, Diff::LCS::ContextDiffCallbacks)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+
+    describe "using Diff::LCS.diff with sdiff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.diff(@s1, @s2, Diff::LCS::SDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.diff(@s2, @s1, Diff::LCS::SDiffCallbacks)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+
+    describe "using Diff::LCS.sdiff with default sdiff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+
+    describe "using Diff::LCS.sdiff with context diff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2, Diff::LCS::ContextDiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1, Diff::LCS::ContextDiffCallbacks)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+
+    describe "using Diff::LCS.xdiff with default diff callbacks" do
+      before(:each) do
+        @patch_set_s1_s2 = Diff::LCS.sdiff(@s1, @s2, Diff::LCS::DiffCallbacks)
+        @patch_set_s2_s1 = Diff::LCS.sdiff(@s2, @s1, Diff::LCS::DiffCallbacks)
+      end
+
+      it "does not autodiscover s1 to s2 patches" do
+        # It should, but it doesn't.
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s1_s2).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+
+        expect do
+          Diff::LCS.patch(@s1, @patch_set_s2_s1).should == @s2
+        end.to raise_error(RuntimeError, /provided patchset/)
+      end
+
+      it "should autodiscover s2 to s1 the left-to-right patches" do
+        Diff::LCS.patch(@s2, @patch_set_s2_s1).should == @s1
+        Diff::LCS.patch(@s2, @patch_set_s1_s2).should == @s1
+      end
+
+      it "should correctly patch left-to-right (explicit patch)" do
+        Diff::LCS.patch(@s1, @patch_set_s1_s2, :patch).should == @s2
+        Diff::LCS.patch(@s2, @patch_set_s2_s1, :patch).should == @s1
+        Diff::LCS.patch!(@s1, @patch_set_s1_s2).should == @s2
+        Diff::LCS.patch!(@s2, @patch_set_s2_s1).should == @s1
+      end
+
+      it "should correctly patch right-to-left (explicit unpatch)" do
+        Diff::LCS.patch(@s2, @patch_set_s1_s2, :unpatch).should == @s1
+        Diff::LCS.patch(@s1, @patch_set_s2_s1, :unpatch).should == @s2
+        Diff::LCS.unpatch!(@s2, @patch_set_s1_s2).should == @s1
+        Diff::LCS.unpatch!(@s1, @patch_set_s2_s1).should == @s2
+      end
+    end
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/diff_lcs_sdiff_spec.rb b/spec/diff_lcs_sdiff_spec.rb
new file mode 100644
index 0000000..b6a3f10
--- /dev/null
+++ b/spec/diff_lcs_sdiff_spec.rb
@@ -0,0 +1,180 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.sdiff should compare sequences correctly" do
+  include Diff::LCS::SpecHelper::Matchers
+
+  def do_sdiff_comparison(s1, s2, forward_sdiff)
+    sdiff_s1_s2 = Diff::LCS.sdiff(s1, s2)
+    sdiff_s2_s1 = Diff::LCS.sdiff(s2, s1)
+
+    sdiff_s1_s2.should == context_diff(forward_sdiff)
+    sdiff_s2_s1.should == context_diff(reverse_sdiff(forward_sdiff))
+  end
+
+  it "sequence-a" do
+    do_sdiff_comparison(seq1, seq2, correct_forward_sdiff)
+  end
+
+  it "sequence-b" do
+    s1 = %w(abc def yyy xxx ghi jkl)
+    s2 = %w(abc dxf xxx ghi jkl)
+    forward_sdiff = [
+      [ '=', [ 0, 'abc' ], [ 0, 'abc' ] ],
+      [ '!', [ 1, 'def' ], [ 1, 'dxf' ] ],
+      [ '-', [ 2, 'yyy' ], [ 2,  nil  ] ],
+      [ '=', [ 3, 'xxx' ], [ 2, 'xxx' ] ],
+      [ '=', [ 4, 'ghi' ], [ 3, 'ghi' ] ],
+      [ '=', [ 5, 'jkl' ], [ 4, 'jkl' ] ]
+    ]
+
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-c" do
+    s1 = %w(a b c d e)
+    s2 = %w(a e)
+    forward_sdiff = [
+      [ '=', [ 0, 'a' ], [ 0, 'a' ] ],
+      [ '-', [ 1, 'b' ], [ 1, nil ] ],
+      [ '-', [ 2, 'c' ], [ 1, nil ] ],
+      [ '-', [ 3, 'd' ], [ 1, nil ] ],
+      [ '=', [ 4, 'e' ], [ 1, 'e' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-d" do
+    s1 = %w(a e)
+    s2 = %w(a b c d e)
+    forward_sdiff = [
+      [ '=', [ 0, 'a' ], [ 0, 'a' ] ],
+      [ '+', [ 1, nil ], [ 1, 'b' ] ],
+      [ '+', [ 1, nil ], [ 2, 'c' ] ],
+      [ '+', [ 1, nil ], [ 3, 'd' ] ],
+      [ '=', [ 1, 'e' ], [ 4, 'e' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-e" do
+    s1 = %w(v x a e)
+    s2 = %w(w y a b c d e)
+    forward_sdiff = [
+      [ '!', [ 0, 'v' ], [ 0, 'w' ] ],
+      [ '!', [ 1, 'x' ], [ 1, 'y' ] ],
+      [ '=', [ 2, 'a' ], [ 2, 'a' ] ],
+      [ '+', [ 3, nil ], [ 3, 'b' ] ],
+      [ '+', [ 3, nil ], [ 4, 'c' ] ],
+      [ '+', [ 3, nil ], [ 5, 'd' ] ],
+      [ '=', [ 3, 'e' ], [ 6, 'e' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-f" do
+    s1 = %w(x a e)
+    s2 = %w(a b c d e)
+    forward_sdiff = [
+      [ '-', [ 0, 'x' ], [ 0, nil ] ],
+      [ '=', [ 1, 'a' ], [ 0, 'a' ] ],
+      [ '+', [ 2, nil ], [ 1, 'b' ] ],
+      [ '+', [ 2, nil ], [ 2, 'c' ] ],
+      [ '+', [ 2, nil ], [ 3, 'd' ] ],
+      [ '=', [ 2, 'e' ], [ 4, 'e' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-g" do
+    s1 = %w(a e)
+    s2 = %w(x a b c d e)
+    forward_sdiff = [
+      [ '+', [ 0, nil ], [ 0, 'x' ] ],
+      [ '=', [ 0, 'a' ], [ 1, 'a' ] ],
+      [ '+', [ 1, nil ], [ 2, 'b' ] ],
+      [ '+', [ 1, nil ], [ 3, 'c' ] ],
+      [ '+', [ 1, nil ], [ 4, 'd' ] ],
+      [ '=', [ 1, 'e' ], [ 5, 'e' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-h" do
+    s1 = %w(a e v)
+    s2 = %w(x a b c d e w x)
+    forward_sdiff = [
+      [ '+', [ 0, nil ], [ 0, 'x' ] ],
+      [ '=', [ 0, 'a' ], [ 1, 'a' ] ],
+      [ '+', [ 1, nil ], [ 2, 'b' ] ],
+      [ '+', [ 1, nil ], [ 3, 'c' ] ],
+      [ '+', [ 1, nil ], [ 4, 'd' ] ],
+      [ '=', [ 1, 'e' ], [ 5, 'e' ] ],
+      [ '!', [ 2, 'v' ], [ 6, 'w' ] ],
+      [ '+', [ 3, nil ], [ 7, 'x' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-i" do
+    s1 = %w()
+    s2 = %w(a b c)
+    forward_sdiff = [
+      [ '+', [ 0, nil ], [ 0, 'a' ] ],
+      [ '+', [ 0, nil ], [ 1, 'b' ] ],
+      [ '+', [ 0, nil ], [ 2, 'c' ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-j" do
+    s1 = %w(a b c)
+    s2 = %w()
+    forward_sdiff = [
+      [ '-', [ 0, 'a' ], [ 0, nil ] ],
+      [ '-', [ 1, 'b' ], [ 0, nil ] ],
+      [ '-', [ 2, 'c' ], [ 0, nil ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-k" do
+    s1 = %w(a b c)
+    s2 = %w(1)
+    forward_sdiff = [
+      [ '!', [ 0, 'a' ], [ 0, '1' ] ],
+      [ '-', [ 1, 'b' ], [ 1, nil ] ],
+      [ '-', [ 2, 'c' ], [ 1, nil ] ] ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-l" do
+    s1 = %w(a b c)
+    s2 = %w(c)
+    forward_sdiff = [
+      [ '-', [ 0, 'a' ], [ 0, nil ] ],
+      [ '-', [ 1, 'b' ], [ 0, nil ] ],
+      [ '=', [ 2, 'c' ], [ 0, 'c' ] ]
+    ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-m" do
+    s1 = %w(abcd efgh ijkl mnop)
+    s2 = []
+    forward_sdiff = [
+      [ '-', [ 0, 'abcd' ], [ 0, nil ] ],
+      [ '-', [ 1, 'efgh' ], [ 0, nil ] ],
+      [ '-', [ 2, 'ijkl' ], [ 0, nil ] ],
+      [ '-', [ 3, 'mnop' ], [ 0, nil ] ]
+    ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+
+  it "sequence-n" do
+    s1 = []
+    s2 = %w(abcd efgh ijkl mnop)
+    forward_sdiff = [
+      [ '+', [ 0, nil ], [ 0, 'abcd' ] ],
+      [ '+', [ 0, nil ], [ 1, 'efgh' ] ],
+      [ '+', [ 0, nil ], [ 2, 'ijkl' ] ],
+      [ '+', [ 0, nil ], [ 3, 'mnop' ] ]
+    ]
+    do_sdiff_comparison(s1, s2, forward_sdiff)
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/diff_lcs_sequences_spec.rb b/spec/diff_lcs_sequences_spec.rb
new file mode 100644
index 0000000..c7a5558
--- /dev/null
+++ b/spec/diff_lcs_sequences_spec.rb
@@ -0,0 +1,83 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'spec_helper'
+
+describe "Diff::LCS.traverse_sequences" do
+  describe "callback with no finishers" do
+    before(:each) do
+      @callback_s1_s2 = simple_callback_no_finishers
+      Diff::LCS.traverse_sequences(seq1, seq2, @callback_s1_s2)
+
+      @callback_s2_s1 = simple_callback_no_finishers
+      Diff::LCS.traverse_sequences(seq2, seq1, @callback_s2_s1)
+    end
+
+    it "should have the correct LCS result on left-matches" do
+      @callback_s1_s2.matched_a.should == correct_lcs
+      @callback_s2_s1.matched_a.should == correct_lcs
+    end
+
+    it "should have the correct LCS result on right-matches" do
+      @callback_s1_s2.matched_b.should == correct_lcs
+      @callback_s2_s1.matched_b.should == correct_lcs
+    end
+
+    it "should have the correct skipped sequences for the left sequence" do
+      @callback_s1_s2.discards_a.should == skipped_seq1
+      @callback_s2_s1.discards_a.should == skipped_seq2
+    end
+
+    it "should have the correct skipped sequences for the right sequence" do
+      @callback_s1_s2.discards_b.should == skipped_seq2
+      @callback_s2_s1.discards_b.should == skipped_seq1
+    end
+
+    it "should not have anything done markers from the left or right sequences" do
+      @callback_s1_s2.done_a.should be_empty
+      @callback_s1_s2.done_b.should be_empty
+      @callback_s2_s1.done_a.should be_empty
+      @callback_s2_s1.done_b.should be_empty
+    end
+  end
+
+  describe "callback with finisher" do
+    before(:each) do
+      @callback_s1_s2 = simple_callback
+      Diff::LCS.traverse_sequences(seq1, seq2, @callback_s1_s2)
+      @callback_s2_s1 = simple_callback
+      Diff::LCS.traverse_sequences(seq2, seq1, @callback_s2_s1)
+    end
+
+    it "should have the correct LCS result on left-matches" do
+      @callback_s1_s2.matched_a.should == correct_lcs
+      @callback_s2_s1.matched_a.should == correct_lcs
+    end
+
+    it "should have the correct LCS result on right-matches" do
+      @callback_s1_s2.matched_b.should == correct_lcs
+      @callback_s2_s1.matched_b.should == correct_lcs
+    end
+
+    it "should have the correct skipped sequences for the left sequence" do
+      @callback_s1_s2.discards_a.should == skipped_seq1
+      @callback_s2_s1.discards_a.should == skipped_seq2
+    end
+
+    it "should have the correct skipped sequences for the right sequence" do
+      @callback_s1_s2.discards_b.should == skipped_seq2
+      @callback_s2_s1.discards_b.should == skipped_seq1
+    end
+
+    it "should have done markers differently-sized sequences" do
+      @callback_s1_s2.done_a.should == [[ "p", 9, "s", 10 ]]
+      @callback_s1_s2.done_b.should be_empty
+
+      # 20110731 I don't yet understand why this particular behaviour
+      # isn't transitive.
+      @callback_s2_s1.done_a.should be_empty
+      @callback_s2_s1.done_b.should be_empty
+    end
+  end
+end
+
+# vim: ft=ruby
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 0000000..1c934e7
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,270 @@
+# -*- ruby encoding: utf-8 -*-
+
+require 'rubygems'
+require 'bundler'
+
+require 'pathname'
+
+file   = Pathname.new(__FILE__).expand_path
+path   = file.parent
+parent = path.parent
+
+$:.unshift parent.join('lib')
+
+require 'diff-lcs'
+
+module Diff::LCS::SpecHelper
+  def seq1
+    %w(a b c e h j l m n p)
+  end
+
+  def skipped_seq1
+    %w(a h n p)
+  end
+
+  def seq2
+    %w(b c d e f j k l m r s t)
+  end
+
+  def skipped_seq2
+    %w(d f k r s t)
+  end
+
+  def word_sequence
+    %w(abcd efgh ijkl mnopqrstuvwxyz)
+  end
+
+  def correct_lcs
+    %w(b c e j l m)
+  end
+
+  def correct_forward_diff
+    [
+      [ [ '-',  0, 'a' ] ],
+      [ [ '+',  2, 'd' ] ],
+      [ [ '-',  4, 'h' ],
+        [ '+',  4, 'f' ] ],
+      [ [ '+',  6, 'k' ] ],
+      [ [ '-',  8, 'n' ],
+        [ '-',  9, 'p' ],
+        [ '+',  9, 'r' ],
+        [ '+', 10, 's' ],
+        [ '+', 11, 't' ] ]
+    ]
+  end
+
+  def correct_backward_diff
+    [
+      [ [ '+',  0, 'a' ] ],
+      [ [ '-',  2, 'd' ] ],
+      [ [ '-',  4, 'f' ],
+        [ '+',  4, 'h' ] ],
+      [ [ '-',  6, 'k' ] ],
+      [
+        [ '-',  9, 'r' ],
+        [ '-', 10, 's' ],
+        [ '+',  8, 'n' ],
+        [ '-', 11, 't' ],
+        [ '+',  9, 'p' ] ]
+    ]
+  end
+
+  def correct_forward_sdiff
+    [
+      [ '-', [  0, 'a' ], [  0, nil ] ],
+      [ '=', [  1, 'b' ], [  0, 'b' ] ],
+      [ '=', [  2, 'c' ], [  1, 'c' ] ],
+      [ '+', [  3, nil ], [  2, 'd' ] ],
+      [ '=', [  3, 'e' ], [  3, 'e' ] ],
+      [ '!', [  4, 'h' ], [  4, 'f' ] ],
+      [ '=', [  5, 'j' ], [  5, 'j' ] ],
+      [ '+', [  6, nil ], [  6, 'k' ] ],
+      [ '=', [  6, 'l' ], [  7, 'l' ] ],
+      [ '=', [  7, 'm' ], [  8, 'm' ] ],
+      [ '!', [  8, 'n' ], [  9, 'r' ] ],
+      [ '!', [  9, 'p' ], [ 10, 's' ] ],
+      [ '+', [ 10, nil ], [ 11, 't' ] ]
+    ]
+  end
+
+  def reverse_sdiff(forward_sdiff)
+    forward_sdiff.map { |line|
+      line[1], line[2] = line[2], line[1]
+      case line[0]
+      when '-' then line[0] = '+'
+      when '+' then line[0] = '-'
+      end
+      line
+    }
+  end
+
+  def change_diff(diff)
+    map_diffs(diff, Diff::LCS::Change)
+  end
+
+  def context_diff(diff)
+    map_diffs(diff, Diff::LCS::ContextChange)
+  end
+
+  def format_diffs(diffs)
+    diffs.map do |e|
+      if e.kind_of?(Array)
+        e.map { |f| f.to_a.join }.join(", ")
+      else
+        e.to_a.join
+      end
+    end.join("\n")
+  end
+
+  def map_diffs(diffs, klass = Diff::LCS::ContextChange)
+    diffs.map do |chunks|
+      if klass == Diff::LCS::ContextChange
+        klass.from_a(chunks)
+      else
+        chunks.map { |changes| klass.from_a(changes) }
+      end
+    end
+  end
+
+  def simple_callback
+    callbacks = Object.new
+    class << callbacks
+      attr_reader :matched_a
+      attr_reader :matched_b
+      attr_reader :discards_a
+      attr_reader :discards_b
+      attr_reader :done_a
+      attr_reader :done_b
+
+      def reset
+        @matched_a = []
+        @matched_b = []
+        @discards_a = []
+        @discards_b = []
+        @done_a = []
+        @done_b = []
+      end
+
+      def match(event)
+        @matched_a << event.old_element
+        @matched_b << event.new_element
+      end
+
+      def discard_b(event)
+        @discards_b << event.new_element
+      end
+
+      def discard_a(event)
+        @discards_a << event.old_element
+      end
+
+      def finished_a(event)
+        @done_a << [event.old_element, event.old_position,
+          event.new_element, event.new_position]
+      end
+
+      def finished_b(event)
+        p "called #finished_b"
+        @done_b << [event.old_element, event.old_position,
+          event.new_element, event.new_position]
+      end
+    end
+    callbacks.reset
+    callbacks
+  end
+
+  def simple_callback_no_finishers
+    simple = simple_callback
+    class << simple
+      undef :finished_a
+      undef :finished_b
+    end
+    simple
+  end
+
+  def balanced_callback
+    cb = Object.new
+    class << cb
+      attr_reader :result
+
+      def reset
+        @result = []
+      end
+
+      def match(event)
+        @result << [ "=", event.old_position, event.new_position ]
+      end
+
+      def discard_a(event)
+        @result << [ "<", event.old_position, event.new_position ]
+      end
+
+      def discard_b(event)
+        @result << [ ">", event.old_position, event.new_position ]
+      end
+
+      def change(event)
+        @result << [ "!", event.old_position, event.new_position ]
+      end
+    end
+    cb.reset
+    cb
+  end
+
+  def balanced_callback_no_change
+    balanced = balanced_callback
+    class << balanced
+      undef :change
+    end
+    balanced
+  end
+
+  module Matchers
+    extend RSpec::Matchers::DSL
+
+    matcher :be_nil_or_match_values do |ii, s1, s2|
+      match do |ee|
+        ee.should satisfy { |vee| vee.nil? || s1[ii] == s2[ee] }
+      end
+    end
+
+    matcher :correctly_map_sequence do |s1|
+      match do |actual|
+        actual.each_with_index { |ee, ii|
+          ee.should be_nil_or_match_values(ii, s1, @s2)
+        }
+      end
+
+      chain :to_other_sequence do |s2|
+        @s2 = s2
+      end
+    end
+  end
+end
+
+RSpec.configure do |conf|
+  conf.include Diff::LCS::SpecHelper
+end
+
+
+=begin
+RSpec::Matchers.define :be_a_multiple_of do |expected|
+  match do |actual|
+    actual % expected == 0
+  end
+
+  failure_message_for_should do |actual|
+    "expected that #{actual} would be a multiple of #{expected}"
+  end
+
+  failure_message_for_should_not do |actual|
+    "expected that #{actual} would not be a multiple of #{expected}"
+  end
+
+  description do
+    "be multiple of #{expected}"
+  end
+end
+=end
+
+# vim: ft=ruby