public void RemoveKeysAsync()
{
// Arrange
const string key1 = "TestKey1";
const string key2 = "TestKey2";
const string key3 = "TestKey3";
_sut.Clear();
var item1 = new TestObject(1, "Jane Smith");
var item2 = new TestObject(2, "John Smith");
var item3 = new TestObject(3, "Jade Smith");
_sut.SetItem(key1, item1);
_sut.SetItem(key2, item2);
_sut.SetItem(key3, item3);
// Act
var keyNames = new string[] { key1, key2 };
_sut.RemoveItemsAsync(keyNames).AsTask().Wait();
// Assert
Assert.Equal(1, _sut.Length());
Assert.NotNull(_sut.GetItem <TestObject>(key3));
}