public void TestHashCodeAndEquals()
{
var k1 = new ValueKey("A", 5);
var k2 = new ValueKey("A", 5);
Assert.Equal(k1.GetHashCode(), k2.GetHashCode());
Assert.True(k1.Equals(k2));
var k3 = new ValueKey("row_1", "col_1");
var k4 = new ValueKey("row_1", "col_1");
Assert.Equal(k3.GetHashCode(), k4.GetHashCode());
Assert.NotEqual(k1.GetHashCode(), k3.GetHashCode());
Assert.True(k3.Equals(k4));
Assert.False(k4.Equals(k2));
var k5 = new ValueKey("row_2", "col_1");
Assert.NotEqual(k4.GetHashCode(), k5.GetHashCode());
Assert.False(k5.Equals(k3));
Assert.False(k5.Equals(null));
Assert.True(Key.IsEmpty(Key.Empty));
Assert.False(Key.IsEmpty(1));
Assert.False(Key.IsEmpty(null));
Assert.True(Key.Equals("A", "A"));
Assert.False(Key.Equals("A", "B"));
Assert.False(Key.Equals("A", null));
Assert.False(Key.Equals(null, "A"));
Assert.True(Key.Equals(null, null));
}