public new void ToString()
{
var expected =
"R1C1: 1, R1C2: 0, R1C3: 0, R1C4: 0, " + Environment.NewLine +
"R2C1: 0, R2C2: 1, R2C3: 0, R2C4: 0, " + Environment.NewLine +
"R3C1: 0, R3C2: 0, R3C3: 1, R3C4: 0, " + Environment.NewLine +
"R4C1: 0, R4C2: 0, R4C3: 0, R4C4: 1";
Assert.AreEqual(expected, Matrix.Identity.ToString());
}