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diff --git a/spec/rubyspec/library/matrix/permutation_spec.rb b/spec/rubyspec/library/matrix/permutation_spec.rb
new file mode 100644
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+++ b/spec/rubyspec/library/matrix/permutation_spec.rb
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+require File.expand_path('../../../spec_helper', __FILE__)
+require 'matrix'
+
+describe "Matrix#permutation?" do
+  it "returns true for a permutation Matrix" do
+    Matrix[[0, 1, 0], [0, 0, 1], [1, 0, 0]].permutation?.should be_true
+  end
+
+  it "returns false for a non permutation square Matrix" do
+    Matrix[[0, 1], [0, 0]].permutation?.should be_false
+    Matrix[[-1, 0], [0, -1]].permutation?.should be_false
+    Matrix[[1, 0], [1, 0]].permutation?.should be_false
+    Matrix[[1, 0], [1, 1]].permutation?.should be_false
+  end
+
+  it "returns true for an empty 0x0 matrix" do
+    Matrix.empty(0,0).permutation?.should be_true
+  end
+
+  it "raises an error for rectangular matrices" do
+    [
+      Matrix[[0], [0]],
+      Matrix[[0, 0]],
+      Matrix.empty(0, 2),
+      Matrix.empty(2, 0),
+    ].each do |rectangual_matrix|
+      lambda {
+        rectangual_matrix.permutation?
+      }.should raise_error(Matrix::ErrDimensionMismatch)
+    end
+  end
+end