public void IsEmpty() { Assert.True(CollectionExtensions.IsEmpty((IReadOnlyCollection <int>)null)); Assert.True(CollectionExtensions.IsEmpty((IReadOnlyCollection <int>) new List <int>())); Assert.False(CollectionExtensions.IsEmpty((IReadOnlyCollection <int>) new List <int> { 1 })); Assert.True(CollectionExtensions.IsEmpty((ICollection <int>)null)); Assert.True(CollectionExtensions.IsEmpty((ICollection <int>) new List <int>())); Assert.False(CollectionExtensions.IsEmpty((ICollection <int>) new List <int> { 1 })); Assert.True(CollectionExtensions.IsEmpty((string)null)); Assert.True(CollectionExtensions.IsEmpty("")); Assert.False(CollectionExtensions.IsEmpty("1")); Assert.True(CollectionExtensions.IsEmpty((IEnumerable <int>)null)); Assert.True(CollectionExtensions.IsEmpty(Enumerable.Empty <int>())); Assert.False(CollectionExtensions.IsEmpty(Enumerable.Repeat(1, 1))); }