1 files changed, 38 insertions, 0 deletions
diff --git a/spec/ruby/library/matrix/shared/inverse.rb b/spec/ruby/library/matrix/shared/inverse.rb
new file mode 100644
index 0000000000..c6996df4a3
--- /dev/null
+++ b/spec/ruby/library/matrix/shared/inverse.rb
@@ -0,0 +1,38 @@
+require File.expand_path('../../fixtures/classes', __FILE__)
+require 'matrix'
+
+describe :inverse, shared: true do
+
+  it "returns a Matrix" do
+    Matrix[ [1,2], [2,1] ].send(@method).should be_an_instance_of(Matrix)
+  end
+
+  it "returns the inverse of the Matrix" do
+    Matrix[
+      [1, 3, 3],     [1, 4, 3],  [1, 3, 4]
+    ].send(@method).should ==
+    Matrix[
+      [7, -3, -3],   [-1, 1, 0], [-1, 0, 1]
+    ]
+  end
+
+  it "returns the inverse of the Matrix (other case)" do
+    Matrix[
+      [1, 2, 3],    [0, 1, 4],     [5, 6, 0]
+    ].send(@method).should be_close_to_matrix([
+      [-24, 18, 5], [20, -15, -4], [-5, 4, 1]
+    ])
+  end
+
+  it "raises a ErrDimensionMismatch if the Matrix is not square" do
+    lambda{
+      Matrix[ [1,2,3], [1,2,3] ].send(@method)
+    }.should raise_error(Matrix::ErrDimensionMismatch)
+  end
+
+  describe "for a subclass of Matrix" do
+    it "returns an instance of that subclass" do
+      MatrixSub.ins.send(@method).should be_an_instance_of(MatrixSub)
+    end
+  end
+end