From 2a65026c0585b07223213a44f64fa730b642dbd7 Mon Sep 17 00:00:00 2001
From: poune05 <poune05@hotmail.com>
Date: Sat, 20 Oct 2018 19:41:49 +0200
Subject: [PATCH] Add Intersect method and tests #47

---
 ShittyLINQ/Intersect.cs           | 32 +++++++++++++++++
 ShittyLinqTests/IntersectTests.cs | 58 +++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 ShittyLINQ/Intersect.cs
 create mode 100644 ShittyLinqTests/IntersectTests.cs

diff --git a/ShittyLINQ/Intersect.cs b/ShittyLINQ/Intersect.cs
new file mode 100644
index 0000000..c4545b3
--- /dev/null
+++ b/ShittyLINQ/Intersect.cs
@@ -0,0 +1,32 @@
+namespace ShittyLINQ
+{
+    using System;
+    using System.Collections.Generic;
+
+    public static partial class Extensions
+    {
+        public static IEnumerable<T> Intersect<T>(this IEnumerable<T> self, IEnumerable<T> second)
+        {
+            return Intersect(self, second, EqualityComparer<T>.Default);
+        }
+
+        public static IEnumerable<T> Intersect<T>(this IEnumerable<T> self, IEnumerable<T> second, IEqualityComparer<T> comparer)
+        {
+            if (self == null)
+                throw new ArgumentNullException(nameof(self));
+            if (second == null)
+                throw new ArgumentNullException(nameof(second));
+
+            foreach (var item in self)
+            {
+                foreach (var secondItem in second)
+                {
+                    if (comparer.Equals(item, secondItem))
+                    {
+                        yield return item;
+                    }
+                }
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/ShittyLinqTests/IntersectTests.cs b/ShittyLinqTests/IntersectTests.cs
new file mode 100644
index 0000000..de4cb49
--- /dev/null
+++ b/ShittyLinqTests/IntersectTests.cs
@@ -0,0 +1,58 @@
+namespace ShittyTests
+{
+    using Microsoft.VisualStudio.TestTools.UnitTesting;
+    using ShittyLINQ;
+    using ShittyTests.TestHelpers;
+
+    [TestClass]
+    public class IntersectTests
+    {
+        [TestMethod]
+        public void Intersect_ReturnsExpected()
+        {
+            var first = new[] { 1, 2, 3, 4, 5 };
+            var second = new[] { 1, 2, 5, 6, 7 };
+            var expectedResult = new[] { 1, 2, 5 };
+
+            var result = first.Intersect(second);
+
+            TestHelper.AssertCollectionsAreSame(expectedResult, result);
+        }
+
+        [TestMethod]
+        public void Intersect_ReturnsExpectedWithFirstCollectionEmpty()
+        {
+            var first = new int[] { };
+            var second = new[] { 1, 2, 5, 6, 7 };
+            var expectedResult = new int[] { };
+
+            var result = first.Intersect(second);
+
+            TestHelper.AssertCollectionsAreSame(expectedResult, result);
+        }
+
+        [TestMethod]
+        public void Intersect_ReturnsExpectedWithSecondCollectionEmpty()
+        {
+            var first = new[] { 1, 2, 3, 4, 5 };
+            var second = new int[] { };
+            var expectedResult = new int[] { };
+
+            var result = first.Intersect(second);
+
+            TestHelper.AssertCollectionsAreSame(expectedResult, result);
+        }
+
+        [TestMethod]
+        public void Intersect_ReturnsExpectedWithoutCommonValue()
+        {
+            var first = new[] { 1, 2, 3, 4, 5 };
+            var second = new int[] { 6, 7, 8, 9, 10 };
+            var expectedResult = new int[] { };
+
+            var result = first.Intersect(second);
+
+            TestHelper.AssertCollectionsAreSame(expectedResult, result);
+        }
+    }
+}