public void ReadonlyDictionaryCantChange()
{
var underTest = new ReadonlyDictionary <string, string>(new Dictionary <string, string> {
{ "a", "a" }
});
Assert.Throws <NotSupportedException>(() => underTest.Remove("b"));
Assert.Throws <NotSupportedException>(() => underTest.Remove(new KeyValuePair <string, string>("b", "b")));
Assert.Throws <NotSupportedException>(() => underTest.Add("b", "b"));
Assert.Throws <NotSupportedException>(() => underTest.Add(new KeyValuePair <string, string>("b", "b")));
Assert.Throws <NotSupportedException>(() => underTest.Clear());
Assert.Throws <NotSupportedException>(() => underTest["a"] = "a");
}