public void Equals() { Variable variable1 = new Variable("X"); Variable variable2 = new Variable("Y"); Variable variable3 = new Variable("X"); Assert.AreEqual(variable1, variable3); Assert.AreEqual(variable3, variable1); Assert.AreEqual(variable1.GetHashCode(), variable3.GetHashCode()); Assert.IsFalse(variable1.Equals(null)); Assert.IsFalse(variable1.Equals(123)); Assert.IsFalse(variable1.Equals("foo")); Assert.AreNotEqual(variable1, variable2); Assert.AreNotEqual(variable2, variable1); }