1 files changed, 12 insertions, 0 deletions
diff --git a/spec/ruby/library/matrix/shared/trace.rb b/spec/ruby/library/matrix/shared/trace.rb
new file mode 100644
index 0000000000..2a42839f5d
--- /dev/null
+++ b/spec/ruby/library/matrix/shared/trace.rb
@@ -0,0 +1,12 @@
+require 'matrix'
+
+describe :trace, shared: true do
+  it "returns the sum of diagonal elements in a square Matrix" do
+    Matrix[[7,6], [3,9]].trace.should == 16
+  end
+
+  it "returns the sum of diagonal elements in a rectangular Matrix" do
+    lambda{ Matrix[[1,2,3], [4,5,6]].trace}.should raise_error(Matrix::ErrDimensionMismatch)
+  end
+
+end