common/UnitTests/Common/Extensions/CollectionExtensionsTests.cs

using System;
using System.Collections.Generic;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace UnitTests.Common.Extensions
{
	[TestClass]
	public class CollectionExtensionsTests
	{
		[TestMethod]
		public void ShouldAddItem()
		{
			// Arrange
			var item = new TestItem { Number = 10, Text = "Ten" };
			ICollection<TestItem> list = new List<TestItem>
			{
				new() {
					Number = 1,
					Text = "One"
				}
			};

			// Act
			list.AddIfNotNull(item);

			// Assert
			Assert.AreEqual(2, list.Count);
		}

		[TestMethod]
		public void ShouldNotAddItem()
		{
			// Arrange
			TestItem item = null;
			ICollection<TestItem> list = new List<TestItem>
			{
				new() {
					Number = 1,
					Text = "One"
				}
			};

			// Act
			list.AddIfNotNull(item);

			// Assert
			Assert.AreEqual(1, list.Count);
		}

		[TestMethod]
		[ExpectedException(typeof(ArgumentNullException))]
		public void ShouldThrowArgumentNullExceptionForNullList()
		{
			// Arrange
			var item = new TestItem { Number = 10, Text = "Ten" };
			ICollection<TestItem> list = null;

			// Act
			list.AddIfNotNull(item);

			// Assert - ArgumentNullException
		}

		[TestMethod]
		public void ShouldAddRange()
		{
			// Arrange
			ICollection<TestItem> items = new List<TestItem>
			{
				new() { Number = 10, Text = "Ten" },
				new() { Number = 11, Text = "Eleven" },
			};
			ICollection<TestItem> list = new List<TestItem>
			{
				new() { Number = 1, Text = "One" },
			};

			// Act
			list.AddRange(items);

			// Assert
			Assert.AreEqual(3, list.Count);
		}

		[TestMethod]
		[ExpectedException(typeof(ArgumentNullException))]
		public void ShouldThrowArgumentNullExceptionForList()
		{
			// Arrange
			ICollection<TestItem> items = new List<TestItem>
			{
				new() { Number = 10, Text = "Ten" },
				new() { Number = 11, Text = "Eleven" },
			};
			ICollection<TestItem> list = null;

			// Act
			list.AddRange(items);

			// Assert - ArgumentNullException
		}

		[TestMethod]
		[ExpectedException(typeof(ArgumentNullException))]
		public void ShouldThrowArgumentNullExceptionForItems()
		{
			// Arrange
			ICollection<TestItem> items = null;
			ICollection<TestItem> list = new List<TestItem>
			{
				new() { Number = 1, Text = "One" },
			};

			// Act
			list.AddRange(items);

			// Assert - ArgumentNullException
		}

		[TestMethod]
		public void ShouldNotAddRange()
		{
			// Arrange
			ICollection<TestItem> list = new List<TestItem>
			{
				new() { Number = 1, Text = "One" },
			};

			// Act
			list.AddRange(list);

			// Assert
			Assert.AreEqual(1, list.Count);
		}

		private class TestItem
		{
			public int Number { get; set; }

			public string Text { get; set; }
		}
	}
}