Matrix multiplication test

Author: jkalias

src/Numerics.Tests/LinearAlgebraTests/Double/DenseMatrixTests.cs

@@ -98,18 +98,14 @@ public void MatrixFrom1DArrayIsReference()
         [Test]
         public void DescriptionForMatrixWithRowsButNoColumns()
         {
-            var matrix = TestMatrices["Tall3x2"];
-            matrix = matrix.RemoveColumn(matrix.ColumnCount - 1);
-            matrix = matrix.RemoveColumn(matrix.ColumnCount - 1);
+            var matrix = GetMatrixWithRowsButNoColumns();
             Assert.AreEqual("DenseMatrix 3x0-Double\r\n[empty]\r\n[empty]\r\n[empty]\r\n", matrix.ToString());
         }
 
         [Test]
         public void DescriptionForMatrixWithColumnsButNoRows()
         {
-            var matrix = TestMatrices["Wide2x3"];
-            matrix = matrix.RemoveRow(matrix.RowCount - 1);
-            matrix = matrix.RemoveRow(matrix.RowCount - 1);
+            var matrix = GetMatrixWithColumnsButNoRows();
             Assert.AreEqual("DenseMatrix 0x3-Double\r\n[empty]  [empty]  [empty]", matrix.ToString());
         }
 
@@ -127,6 +123,15 @@ public void DescriptionForMatrixWithNoRowsAndNoColumns()
             Assert.AreEqual("DenseMatrix 0x0-Double\r\n[empty]", matrix.ToString());
         }
 
+        [Test]
+        public void MatrixMultiplicationWhenMatricesHaveNoRowsAndColumns()
+        {
+            var a = GetMatrixWithRowsButNoColumns();
+            var b = GetMatrixWithColumnsButNoRows();
+            var result = a * b;
+            Assert.AreEqual(new DenseMatrix(3), result);
+        }
+
         /// <summary>
         /// Matrix from two-dimensional array is a copy.
         /// </summary>
@@ -241,5 +246,21 @@ public void MatrixToMatrixString()
                 }
             }
         }
+
+        private Matrix<double> GetMatrixWithRowsButNoColumns()
+        {
+            var matrix = TestMatrices["Tall3x2"];
+            matrix = matrix.RemoveColumn(matrix.ColumnCount - 1);
+            matrix = matrix.RemoveColumn(matrix.ColumnCount - 1);
+            return matrix;
+        }
+
+        private Matrix<double> GetMatrixWithColumnsButNoRows()
+        {
+            var matrix = TestMatrices["Wide2x3"];
+            matrix = matrix.RemoveRow(matrix.RowCount - 1);
+            matrix = matrix.RemoveRow(matrix.RowCount - 1);
+            return matrix;
+        }
     }
 }