Add Queue.

src/data-structures/queue/__test__/Queue.test.js

@@ -0,0 +1,51 @@
+import Queue from '../Queue';
+
+describe('Queue', () => {
+  it('should create empty queue', () => {
+    const queue = new Queue();
+    expect(queue).not.toBeNull();
+    expect(queue.linkedList).not.toBeNull();
+  });
+
+  it('should add data to queue', () => {
+    const queue = new Queue();
+
+    queue.add(1);
+    queue.add(2);
+
+    expect(queue.linkedList.toString()).toBe('1,2');
+  });
+
+  it('should peek data from queue', () => {
+    const queue = new Queue();
+
+    expect(queue.peek()).toBeNull();
+
+    queue.add(1);
+    queue.add(2);
+
+    expect(queue.peek()).toBe(2);
+    expect(queue.peek()).toBe(2);
+  });
+
+  it('should check if queue is empty', () => {
+    const queue = new Queue();
+
+    expect(queue.isEmpty()).toBeTruthy();
+
+    queue.add(1);
+
+    expect(queue.isEmpty()).toBeFalsy();
+  });
+
+  it('should remove from empty', () => {
+    const queue = new Queue();
+
+    queue.add(1);
+    queue.add(2);
+
+    expect(queue.remove()).toBe(2);
+    expect(queue.remove()).toBe(1);
+    expect(queue.isEmpty()).toBeTruthy();
+  });
+});