Created some add/remove test cases

Created test cases for add and remove

Author: maxMyers13

src/_DataStructures_/Set/setTest.js

@@ -0,0 +1,43 @@
+const letters = require('./index');
+
+describe('Data Structure : Set', () => {
+
+
+  it('X Set should be a Class', () => {
+    expect(typeof XSet.prototype.constructor).toEqual('function');
+  });
+  
+  describe('Creation of Set', () => {
+    
+    it('Should create a new Set with no elements', () => {
+      letters = new XSet();
+      expect(letters === 0);
+    });
+    
+    it('Should add letter A', () => {
+      letters.add('a');
+      expect(letters.has('a');
+    });
+    
+    it('Should add letter B', () => {
+      letters.add('b');
+      expect(letters.has('b');
+    });
+    
+    it('Should add letter C', () => {
+      letters.add('c');
+      expect(letters.has('c');
+    });
+    
+    it('Should remove letter A', () => {
+      letters.remove('a');
+      expect(!letters.has('a');
+    });
+    
+    it('Should remove letter B', () => {
+      letters.remove('b');
+      expect(!letters.has('b');
+    });
+
+    
+  });