public void GenerateOneMillionString_WithRngProvider_ShouldBeUnique() { const int count = 1000000; var holder = new string[count]; var rnd = new Random(); using var rngProvider = new RNGCryptoServiceProvider(); for (var i = 0; i < count; i++) { holder[i] = rngProvider.GetString(rnd.Next(10, 30)); } holder.Should().NotBeEmpty().And.NotContainNulls().And.HaveCount(count).And.OnlyHaveUniqueItems(); }