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diff --git a/spec/ruby/library/matrix/each_with_index_spec.rb b/spec/ruby/library/matrix/each_with_index_spec.rb
new file mode 100644
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+++ b/spec/ruby/library/matrix/each_with_index_spec.rb
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+require File.expand_path('../../../spec_helper', __FILE__)
+require 'matrix'
+
+describe "Matrix#each_with_index" do
+  before :all do
+    @m = Matrix[ [1, 2, 3], [4, 5, 6] ]
+    @result = [
+      [1, 0, 0],
+      [2, 0, 1],
+      [3, 0, 2],
+      [4, 1, 0],
+      [5, 1, 1],
+      [6, 1, 2]
+    ]
+  end
+
+  it "returns an Enumerator when called without a block" do
+    enum = @m.each_with_index
+    enum.should be_an_instance_of(Enumerator)
+    enum.to_a.should == @result
+  end
+
+  it "returns self" do
+    @m.each_with_index{}.should equal(@m)
+  end
+
+  it "yields the elements starting with the those of the first row" do
+    a = []
+    @m.each_with_index {|x, r, c| a << [x, r, c]}
+    a.should == @result
+  end
+end
+
+describe "Matrix#each_with_index with an argument" do
+  before :all do
+    @m = Matrix[ [1, 2, 3, 4], [5, 6, 7, 8] ]
+    @t = Matrix[ [1, 2], [3, 4], [5, 6], [7, 8] ]
+  end
+
+  it "raises an ArgumentError for unrecognized argument" do
+    lambda {
+      @m.each_with_index("all"){}
+    }.should raise_error(ArgumentError)
+    lambda {
+      @m.each_with_index(nil){}
+    }.should raise_error(ArgumentError)
+    lambda {
+      @m.each_with_index(:left){}
+    }.should raise_error(ArgumentError)
+  end
+
+  it "yields the rights elements when passed :diagonal" do
+    @m.each_with_index(:diagonal).to_a.should == [[1, 0, 0], [6, 1, 1]]
+    @t.each_with_index(:diagonal).to_a.should == [[1, 0, 0], [4, 1, 1]]
+  end
+
+  it "yields the rights elements when passed :off_diagonal" do
+    @m.each_with_index(:off_diagonal).to_a.should == [[2, 0, 1], [3, 0, 2], [4, 0, 3], [5, 1, 0], [7, 1, 2], [8, 1, 3]]
+    @t.each_with_index(:off_diagonal).to_a.should == [[2, 0, 1], [3, 1, 0], [5, 2, 0], [6, 2, 1], [7, 3, 0], [8, 3, 1]]
+  end
+
+  it "yields the rights elements when passed :lower" do
+    @m.each_with_index(:lower).to_a.should == [[1, 0, 0], [5, 1, 0], [6, 1, 1]]
+    @t.each_with_index(:lower).to_a.should == [[1, 0, 0], [3, 1, 0], [4, 1, 1], [5, 2, 0], [6, 2, 1], [7, 3, 0], [8, 3, 1]]
+  end
+
+  it "yields the rights elements when passed :strict_lower" do
+    @m.each_with_index(:strict_lower).to_a.should == [[5, 1, 0]]
+    @t.each_with_index(:strict_lower).to_a.should == [[3, 1, 0], [5, 2, 0], [6, 2, 1], [7, 3, 0], [8, 3, 1]]
+  end
+
+  it "yields the rights elements when passed :strict_upper" do
+    @m.each_with_index(:strict_upper).to_a.should == [[2, 0, 1], [3, 0, 2], [4, 0, 3], [7, 1, 2], [8, 1, 3]]
+    @t.each_with_index(:strict_upper).to_a.should == [[2, 0, 1]]
+  end
+
+  it "yields the rights elements when passed :upper" do
+    @m.each_with_index(:upper).to_a.should == [[1, 0, 0], [2, 0, 1], [3, 0, 2], [4, 0, 3], [6, 1, 1], [7, 1, 2], [8, 1, 3]]
+    @t.each_with_index(:upper).to_a.should == [[1, 0, 0], [2, 0, 1], [4, 1, 1]]
+  end
+end