From 75e93fd88521cc57723ab0d62550db3f7ddafde7 Mon Sep 17 00:00:00 2001
From: Katherine Hambley <superdesigngirl@mac.com>
Date: Thu, 6 Oct 2022 08:01:48 -0500
Subject: [PATCH] Added CSharp Fibonacci Checker program (#913)

---
 algorithms/CSharp/README.md                   |  1 +
 .../CSharp/src/Maths/fibonacci-checker.cs     | 32 +++++++++++++++++++
 .../test/Maths/fibonacci-checker-tests.cs     | 20 ++++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 algorithms/CSharp/src/Maths/fibonacci-checker.cs
 create mode 100644 algorithms/CSharp/test/Maths/fibonacci-checker-tests.cs

diff --git a/algorithms/CSharp/README.md b/algorithms/CSharp/README.md
index 5f17d0b7..edee912a 100644
--- a/algorithms/CSharp/README.md
+++ b/algorithms/CSharp/README.md
@@ -40,6 +40,7 @@ To run the `.cs` file, kindly use [.Net Finddle](https://dotnetfiddle.net/)
 ## Maths
 
 - [Abundant Number](src/Maths/abundant-number.cs)
+- [Fibonacci Checker](src/Maths/fibonacci-checker.cs)
 - [Naismith's Rule](src/Maths/naismith-rule.cs)
 
 ## Queues
diff --git a/algorithms/CSharp/src/Maths/fibonacci-checker.cs b/algorithms/CSharp/src/Maths/fibonacci-checker.cs
new file mode 100644
index 00000000..61cc94a8
--- /dev/null
+++ b/algorithms/CSharp/src/Maths/fibonacci-checker.cs
@@ -0,0 +1,32 @@
+/* Fibonacci Checker - A program to check whether a number is in the Fibonacci sequence.
+This sequence is defined by: Fn = Fn-1 + Fn-2 (to find Fn, you add the previous two numbers. The program calculates the Fibonacci sequence up to and including the given number. */
+using System;
+
+namespace Algorithms.Maths
+{
+    public class Fibonacci
+    {
+        public static bool Checker(int num)
+        {
+            if (num == 2 || num == 3)
+            {
+                return true;
+            }
+            var num1 = 0;
+            var num2 = 1;
+            var num3 = 1;
+
+            for (var i = 0; i <= num; i++)
+            {
+                if (num1 == num)
+                {
+                    return true;
+                }
+                num1 = num2;
+                num2 = num3;
+                num3 = num1 + num2;
+            }
+            return false;
+        }
+    }
+}
diff --git a/algorithms/CSharp/test/Maths/fibonacci-checker-tests.cs b/algorithms/CSharp/test/Maths/fibonacci-checker-tests.cs
new file mode 100644
index 00000000..25a2c58b
--- /dev/null
+++ b/algorithms/CSharp/test/Maths/fibonacci-checker-tests.cs
@@ -0,0 +1,20 @@
+using NUnit.Framework;
+
+namespace Algorithms.Tests.Maths
+{
+    [TestFixture]
+    internal class Checker
+    {
+        [TestCase(1, true)]
+        [TestCase(3, true)]
+        [TestCase(4, false)]
+        [TestCase(34, true)]
+        [TestCase(70, false)]
+        [TestCase(110, false)]
+        public void FibonacciChecker_ShouldGetExpectedResult(int num, bool expected)
+        {
+            var result = Algorithms.Maths.Fibonacci.Checker(num);
+            Assert.AreEqual(expected, result);
+        }
+    }
+}