diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..fb0b4ac
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,3 @@
+language: node_js
+node_js:
+  - 7
diff --git a/index.js b/index.js
index 80bb5fe..01d7b31 100644
--- a/index.js
+++ b/index.js
@@ -1,19 +1,23 @@
 'use strict';
 
 function add(a, b) {
-    return a + b;
+  return a + b;
 }
 
 function subtract(a, b) {
-    return a - b;
+  return a - b;
 }
 
 function divide(a, b) {
-    return a / b;
+  return a / b;
+}
+function multiply(a, b) {
+  return a * b;
 }
 
 module.exports = {
-    add,
-    subtract,
-    divide
-};
\ No newline at end of file
+  add,
+  subtract,
+  divide,
+  multiply
+};
diff --git a/package-lock.json b/package-lock.json
new file mode 100644
index 0000000..c296d42
--- /dev/null
+++ b/package-lock.json
@@ -0,0 +1,320 @@
+{
+  "name": "calculator",
+  "version": "1.0.0",
+  "lockfileVersion": 1,
+  "requires": true,
+  "dependencies": {
+    "assertion-error": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/assertion-error/-/assertion-error-1.1.0.tgz",
+      "integrity": "sha512-jgsaNduz+ndvGyFt3uSuWqvy4lCnIJiovtouQN5JZHOKCS2QuhEdbcQHFhVksz2N2U9hXJo8odG7ETyWlEeuDw==",
+      "dev": true
+    },
+    "balanced-match": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/balanced-match/-/balanced-match-1.0.0.tgz",
+      "integrity": "sha1-ibTRmasr7kneFk6gK4nORi1xt2c=",
+      "dev": true
+    },
+    "brace-expansion": {
+      "version": "1.1.11",
+      "resolved": "https://registry.npmjs.org/brace-expansion/-/brace-expansion-1.1.11.tgz",
+      "integrity": "sha512-iCuPHDFgrHX7H2vEI/5xpz07zSHB00TpugqhmYtVmMO6518mCuRMoOYFldEBl0g187ufozdaHgWKcYFb61qGiA==",
+      "dev": true,
+      "requires": {
+        "balanced-match": "1.0.0",
+        "concat-map": "0.0.1"
+      }
+    },
+    "browser-stdout": {
+      "version": "1.3.0",
+      "resolved": "https://registry.npmjs.org/browser-stdout/-/browser-stdout-1.3.0.tgz",
+      "integrity": "sha1-81HTKWnTL6XXpVZxVCY9korjvR8=",
+      "dev": true
+    },
+    "chai": {
+      "version": "3.5.0",
+      "resolved": "https://registry.npmjs.org/chai/-/chai-3.5.0.tgz",
+      "integrity": "sha1-TQJjewZ/6Vi9v906QOxW/vc3Mkc=",
+      "dev": true,
+      "requires": {
+        "assertion-error": "1.1.0",
+        "deep-eql": "0.1.3",
+        "type-detect": "1.0.0"
+      }
+    },
+    "commander": {
+      "version": "2.9.0",
+      "resolved": "https://registry.npmjs.org/commander/-/commander-2.9.0.tgz",
+      "integrity": "sha1-nJkJQXbhIkDLItbFFGCYQA/g99Q=",
+      "dev": true,
+      "requires": {
+        "graceful-readlink": "1.0.1"
+      }
+    },
+    "concat-map": {
+      "version": "0.0.1",
+      "resolved": "https://registry.npmjs.org/concat-map/-/concat-map-0.0.1.tgz",
+      "integrity": "sha1-2Klr13/Wjfd5OnMDajug1UBdR3s=",
+      "dev": true
+    },
+    "debug": {
+      "version": "2.6.8",
+      "resolved": "https://registry.npmjs.org/debug/-/debug-2.6.8.tgz",
+      "integrity": "sha1-5zFTHKLt4n0YgiJCfaF4IdaP9Pw=",
+      "dev": true,
+      "requires": {
+        "ms": "2.0.0"
+      }
+    },
+    "deep-eql": {
+      "version": "0.1.3",
+      "resolved": "https://registry.npmjs.org/deep-eql/-/deep-eql-0.1.3.tgz",
+      "integrity": "sha1-71WKyrjeJSBs1xOQbXTlaTDrafI=",
+      "dev": true,
+      "requires": {
+        "type-detect": "0.1.1"
+      },
+      "dependencies": {
+        "type-detect": {
+          "version": "0.1.1",
+          "resolved": "https://registry.npmjs.org/type-detect/-/type-detect-0.1.1.tgz",
+          "integrity": "sha1-C6XsKohWQORw6k6FBZcZANrFiCI=",
+          "dev": true
+        }
+      }
+    },
+    "diff": {
+      "version": "3.2.0",
+      "resolved": "https://registry.npmjs.org/diff/-/diff-3.2.0.tgz",
+      "integrity": "sha1-yc45Okt8vQsFinJck98pkCeGj/k=",
+      "dev": true
+    },
+    "escape-string-regexp": {
+      "version": "1.0.5",
+      "resolved": "https://registry.npmjs.org/escape-string-regexp/-/escape-string-regexp-1.0.5.tgz",
+      "integrity": "sha1-G2HAViGQqN/2rjuyzwIAyhMLhtQ=",
+      "dev": true
+    },
+    "fs.realpath": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/fs.realpath/-/fs.realpath-1.0.0.tgz",
+      "integrity": "sha1-FQStJSMVjKpA20onh8sBQRmU6k8=",
+      "dev": true
+    },
+    "glob": {
+      "version": "7.1.1",
+      "resolved": "https://registry.npmjs.org/glob/-/glob-7.1.1.tgz",
+      "integrity": "sha1-gFIR3wT6rxxjo2ADBs31reULLsg=",
+      "dev": true,
+      "requires": {
+        "fs.realpath": "1.0.0",
+        "inflight": "1.0.6",
+        "inherits": "2.0.4",
+        "minimatch": "3.0.4",
+        "once": "1.4.0",
+        "path-is-absolute": "1.0.1"
+      }
+    },
+    "graceful-readlink": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/graceful-readlink/-/graceful-readlink-1.0.1.tgz",
+      "integrity": "sha1-TK+tdrxi8C+gObL5Tpo906ORpyU=",
+      "dev": true
+    },
+    "growl": {
+      "version": "1.9.2",
+      "resolved": "https://registry.npmjs.org/growl/-/growl-1.9.2.tgz",
+      "integrity": "sha1-Dqd0NxXbjY3ixe3hd14bRayFwC8=",
+      "dev": true
+    },
+    "has-flag": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-1.0.0.tgz",
+      "integrity": "sha1-nZ55MWXOAXoA8AQYxD+UKnsdEfo=",
+      "dev": true
+    },
+    "he": {
+      "version": "1.1.1",
+      "resolved": "https://registry.npmjs.org/he/-/he-1.1.1.tgz",
+      "integrity": "sha1-k0EP0hsAlzUVH4howvJx80J+I/0=",
+      "dev": true
+    },
+    "inflight": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/inflight/-/inflight-1.0.6.tgz",
+      "integrity": "sha1-Sb1jMdfQLQwJvJEKEHW6gWW1bfk=",
+      "dev": true,
+      "requires": {
+        "once": "1.4.0",
+        "wrappy": "1.0.2"
+      }
+    },
+    "inherits": {
+      "version": "2.0.4",
+      "resolved": "https://registry.npmjs.org/inherits/-/inherits-2.0.4.tgz",
+      "integrity": "sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==",
+      "dev": true
+    },
+    "json3": {
+      "version": "3.3.2",
+      "resolved": "https://registry.npmjs.org/json3/-/json3-3.3.2.tgz",
+      "integrity": "sha1-PAQ0dD35Pi9cQq7nsZvLSDV19OE=",
+      "dev": true
+    },
+    "lodash._baseassign": {
+      "version": "3.2.0",
+      "resolved": "https://registry.npmjs.org/lodash._baseassign/-/lodash._baseassign-3.2.0.tgz",
+      "integrity": "sha1-jDigmVAPIVrQnlnxci/QxSv+Ck4=",
+      "dev": true,
+      "requires": {
+        "lodash._basecopy": "3.0.1",
+        "lodash.keys": "3.1.2"
+      }
+    },
+    "lodash._basecopy": {
+      "version": "3.0.1",
+      "resolved": "https://registry.npmjs.org/lodash._basecopy/-/lodash._basecopy-3.0.1.tgz",
+      "integrity": "sha1-jaDmqHbPNEwK2KVIghEd08XHyjY=",
+      "dev": true
+    },
+    "lodash._basecreate": {
+      "version": "3.0.3",
+      "resolved": "https://registry.npmjs.org/lodash._basecreate/-/lodash._basecreate-3.0.3.tgz",
+      "integrity": "sha1-G8ZhYU2qf8MRt9A78WgGoCE8+CE=",
+      "dev": true
+    },
+    "lodash._getnative": {
+      "version": "3.9.1",
+      "resolved": "https://registry.npmjs.org/lodash._getnative/-/lodash._getnative-3.9.1.tgz",
+      "integrity": "sha1-VwvH3t5G1hzc3mh9ZdPuy6o6r/U=",
+      "dev": true
+    },
+    "lodash._isiterateecall": {
+      "version": "3.0.9",
+      "resolved": "https://registry.npmjs.org/lodash._isiterateecall/-/lodash._isiterateecall-3.0.9.tgz",
+      "integrity": "sha1-UgOte6Ql+uhCRg5pbbnPPmqsBXw=",
+      "dev": true
+    },
+    "lodash.create": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/lodash.create/-/lodash.create-3.1.1.tgz",
+      "integrity": "sha1-1/KEnw29p+BGgruM1yqwIkYd6+c=",
+      "dev": true,
+      "requires": {
+        "lodash._baseassign": "3.2.0",
+        "lodash._basecreate": "3.0.3",
+        "lodash._isiterateecall": "3.0.9"
+      }
+    },
+    "lodash.isarguments": {
+      "version": "3.1.0",
+      "resolved": "https://registry.npmjs.org/lodash.isarguments/-/lodash.isarguments-3.1.0.tgz",
+      "integrity": "sha1-L1c9hcaiQon/AGY7SRwdM4/zRYo=",
+      "dev": true
+    },
+    "lodash.isarray": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/lodash.isarray/-/lodash.isarray-3.0.4.tgz",
+      "integrity": "sha1-eeTriMNqgSKvhvhEqpvNhRtfu1U=",
+      "dev": true
+    },
+    "lodash.keys": {
+      "version": "3.1.2",
+      "resolved": "https://registry.npmjs.org/lodash.keys/-/lodash.keys-3.1.2.tgz",
+      "integrity": "sha1-TbwEcrFWvlCgsoaFXRvQsMZWCYo=",
+      "dev": true,
+      "requires": {
+        "lodash._getnative": "3.9.1",
+        "lodash.isarguments": "3.1.0",
+        "lodash.isarray": "3.0.4"
+      }
+    },
+    "minimatch": {
+      "version": "3.0.4",
+      "resolved": "https://registry.npmjs.org/minimatch/-/minimatch-3.0.4.tgz",
+      "integrity": "sha512-yJHVQEhyqPLUTgt9B83PXu6W3rx4MvvHvSUvToogpwoGDOUQ+yDrR0HRot+yOCdCO7u4hX3pWft6kWBBcqh0UA==",
+      "dev": true,
+      "requires": {
+        "brace-expansion": "1.1.11"
+      }
+    },
+    "minimist": {
+      "version": "0.0.8",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-0.0.8.tgz",
+      "integrity": "sha1-hX/Kv8M5fSYluCKCYuhqp6ARsF0=",
+      "dev": true
+    },
+    "mkdirp": {
+      "version": "0.5.1",
+      "resolved": "https://registry.npmjs.org/mkdirp/-/mkdirp-0.5.1.tgz",
+      "integrity": "sha1-MAV0OOrGz3+MR2fzhkjWaX11yQM=",
+      "dev": true,
+      "requires": {
+        "minimist": "0.0.8"
+      }
+    },
+    "mocha": {
+      "version": "3.5.3",
+      "resolved": "https://registry.npmjs.org/mocha/-/mocha-3.5.3.tgz",
+      "integrity": "sha512-/6na001MJWEtYxHOV1WLfsmR4YIynkUEhBwzsb+fk2qmQ3iqsi258l/Q2MWHJMImAcNpZ8DEdYAK72NHoIQ9Eg==",
+      "dev": true,
+      "requires": {
+        "browser-stdout": "1.3.0",
+        "commander": "2.9.0",
+        "debug": "2.6.8",
+        "diff": "3.2.0",
+        "escape-string-regexp": "1.0.5",
+        "glob": "7.1.1",
+        "growl": "1.9.2",
+        "he": "1.1.1",
+        "json3": "3.3.2",
+        "lodash.create": "3.1.1",
+        "mkdirp": "0.5.1",
+        "supports-color": "3.1.2"
+      }
+    },
+    "ms": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz",
+      "integrity": "sha1-VgiurfwAvmwpAd9fmGF4jeDVl8g=",
+      "dev": true
+    },
+    "once": {
+      "version": "1.4.0",
+      "resolved": "https://registry.npmjs.org/once/-/once-1.4.0.tgz",
+      "integrity": "sha1-WDsap3WWHUsROsF9nFC6753Xa9E=",
+      "dev": true,
+      "requires": {
+        "wrappy": "1.0.2"
+      }
+    },
+    "path-is-absolute": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/path-is-absolute/-/path-is-absolute-1.0.1.tgz",
+      "integrity": "sha1-F0uSaHNVNP+8es5r9TpanhtcX18=",
+      "dev": true
+    },
+    "supports-color": {
+      "version": "3.1.2",
+      "resolved": "https://registry.npmjs.org/supports-color/-/supports-color-3.1.2.tgz",
+      "integrity": "sha1-cqJiiU2dQIuVbKBf83su2KbiotU=",
+      "dev": true,
+      "requires": {
+        "has-flag": "1.0.0"
+      }
+    },
+    "type-detect": {
+      "version": "1.0.0",
+      "resolved": "https://registry.npmjs.org/type-detect/-/type-detect-1.0.0.tgz",
+      "integrity": "sha1-diIXzAbbJY7EiQihKY6LlRIejqI=",
+      "dev": true
+    },
+    "wrappy": {
+      "version": "1.0.2",
+      "resolved": "https://registry.npmjs.org/wrappy/-/wrappy-1.0.2.tgz",
+      "integrity": "sha1-tSQ9jz7BqjXxNkYFvA0QNuMKtp8=",
+      "dev": true
+    }
+  }
+}
diff --git a/package.json b/package.json
index 9761aa9..c362db5 100644
--- a/package.json
+++ b/package.json
@@ -9,8 +9,8 @@
   "keywords": [
     "calculator"
   ],
-  "author": "Andrew Chalkley <andrew@chalkley.org> (http://forefront.io/)",
-  "license": "MIT",
+  "author": "Mohamad .farhani",
+  "license": "so0oshiance",
   "devDependencies": {
     "chai": "^3.5.0",
     "mocha": "^3.0.2"
diff --git a/test/test_calculator_multiplication.js b/test/test_calculator_multiplication.js
index 50f9511..c9f6c0b 100644
--- a/test/test_calculator_multiplication.js
+++ b/test/test_calculator_multiplication.js
@@ -1,11 +1,18 @@
 'use strict';
 
-const {assert} = require('chai');
+const { assert } = require('chai');
+const { multiply } = require('../');
 
 describe('multiply()', () => {
-    it('should multiply positive numbers together');
+  it('should multiply positive numbers together', () => {
+    assert.equal(multiply(2, 3), 6);
+  });
 
-    it('should multiply positive and negative numbers together');
+  it('should multiply positive and negative numbers together', () => {
+    assert.equal(multiply(2, -3), -6);
+  });
 
-    it('should multiply negative numbers together');
-});
\ No newline at end of file
+  it('should multiply negative numbers together', () => {
+    assert.equal(multiply(-2, -3), 6);
+  });
+});