diff --git a/index.spec.ts b/index.spec.ts
index e69de29..9ff452a 100644
--- a/index.spec.ts
+++ b/index.spec.ts
@@ -0,0 +1,125 @@
+/*!
+ * Daylight - is a tiny JavaScript library for basic sun/moon position/times/phase calculations.
+ * https://github.com/modern-dev/daylight
+ *
+ * Copyright (c) 2020 Bohdan Shtepan
+ * Licensed under the MIT license.
+ */
+
+import { sun, moon } from './index';
+import { expect, use } from 'chai';
+import 'mocha';
+
+use(require('chai-almost')(0.01));
+use(require('chai-datetime'));
+
+describe('daylight', () => {
+  let date: Date;
+  let latitude: number;
+  let longitude: number;
+  
+  beforeEach(() => {
+    date = new Date(2019, 1, 9, 20); // 9th of February, 2019
+    latitude = 40.74; // New York, Manhattan
+    longitude = 74.00;
+  });
+
+  describe('sun object', () => {
+    it('should calculate sun\'s position correctly', () => {
+      const position = sun.getPosition(date, latitude, longitude);
+      const expectedPosition = {
+        azimuth: 2.46,
+        altitude: -1.03
+      };
+
+      expect(position).not.to.be.null;
+      expect(position.azimuth).to.almost.equal(expectedPosition.azimuth);
+      expect(position.altitude).to.almost.equal(expectedPosition.altitude);
+    });
+
+    it('should calculate sun\'s times correctly', () => {
+      const times = sun.getTimes(date, latitude, longitude);
+      const expectedTimes = {
+        dawn: new Date('2019-02-09T01:39:11.109Z'),
+        dusk: new Date('2019-02-09T12:59:55.406Z'),
+        sunrise: {
+          end: new Date('2019-02-09T02:10:39.261Z')
+        },
+        sunset: {
+          start: new Date('2019-02-09T12:28:27.253Z')
+        },
+        nauticalDawn: {
+          start: new Date('2019-02-09T01:06:48.219Z')
+        },
+        nauticalDusk: {
+          end: new Date('2019-02-09T13:32:18.296Z')
+        }
+      };
+  
+      expect(times).not.to.be.null;
+      expect(times.dawn).to.equalDate(expectedTimes.dawn);
+      expect(times.dusk).to.equalDate(expectedTimes.dusk);
+      expect(times.sunset.start).to.equalDate(expectedTimes.sunset.start);
+      expect(times.sunrise.end).to.equalDate(expectedTimes.sunrise.end);
+      expect(times.nauticalDawn.start).to.equalDate(expectedTimes.nauticalDawn.start);
+      expect(times.nauticalDusk.end).to.equalDate(expectedTimes.nauticalDusk.end);
+    });
+  });
+  
+  describe('moon object', () => {
+    it('should calculate moon\'s position correctly', () => {
+      const position = moon.getPosition(date, latitude, longitude);
+      const expectedValues = {
+        azimuth: 1.79,
+        altitude: -0.22,
+        distance: 395825.55,
+        parallacticAngle: 0.83,
+        latitude: -5.03,
+        longitude: 10.08,
+        zodiacSign: 'Aries'
+      };
+  
+      expect(position).not.to.be.null;
+      expect(position.azimuth).to.almost.equal(expectedValues.azimuth);
+      expect(position.altitude).to.almost.equal(expectedValues.altitude);
+      expect(position.distance).to.almost.equal(expectedValues.distance);
+      expect(position.parallacticAngle).to.almost.equal(expectedValues.parallacticAngle);
+      expect(position.latitude).to.almost.equal(expectedValues.latitude);
+      expect(position.longitude).to.almost.equal(expectedValues.longitude);
+      expect(position.zodiacSign).to.be.equal(expectedValues.zodiacSign);
+    });
+  
+    it('should calculate moon\'s phase correctly', () => {
+      const phase = moon.getPhase(date);
+      const expectedPhase = {
+        fraction: 0.21,
+        phase: 0.15,
+        angle: -1.90
+      };
+  
+      expect(phase).not.to.be.null;
+      expect(phase.fraction).to.almost.equal(expectedPhase.fraction);
+      expect(phase.phase).to.almost.equal(expectedPhase.phase);
+      expect(phase.angle).to.almost.equal(expectedPhase.angle);
+    });
+  
+    it('should calculate moon\'s times correctly', () => {
+      const times = moon.getTimes(date, latitude, longitude);
+      const expectedTimes = {
+        moonrise: new Date('2019-02-09T04:29:37.076Z'),
+        moonset: new Date('2019-02-09T16:50:15.974Z')
+      };
+      
+      expect(times).not.to.be.null;
+      expect(times.moonrise).to.equalDate(expectedTimes.moonrise);
+      expect(times.moonset).to.equalDate(expectedTimes.moonset);
+    });
+
+    it('should calculate moon is always down on the South Pole', () => {
+      const times = moon.getTimes(new Date(2019, 0, 1), 90, 45);
+
+      expect(times).not.to.be.null;
+      expect(times.alwaysDown).to.be.true;
+    });
+  });
+});