diff --git a/__tests__/api.test.js b/__tests__/api.test.js
new file mode 100644
index 0000000..e7d1a65
--- /dev/null
+++ b/__tests__/api.test.js
@@ -0,0 +1,75 @@
+import APIpeline from '../dist/index';
+import 'whatwg-fetch';
+import exampleData from './static/example';
+import server from './server';
+
+const API_OPTIONS = {
+  fetchMethod: window.fetch,
+  domains: { default: 'http://127.0.0.1:23135' }
+};
+
+const API_SERVICES = {
+  testHeaders: { path: 'testHeaders' },
+  getExample: { path: 'example.json' },
+  postExample: { path: 'postExample', method: 'POST' }
+};
+
+
+describe('>>> Test API calls', () => {
+  let mockedServer;
+  beforeAll((done) => {
+    mockedServer = server.listen(23135, done);
+  });
+
+  afterAll((done) => {
+    mockedServer.close(done);
+  });
+
+  it('Returns headers', async () => {
+    const api = new APIpeline(API_OPTIONS, API_SERVICES);
+    try {
+      await expect(
+        api.get('testHeaders', { headers: { 'Content-Type': 'application/pdf' } })
+      ).resolves.toHaveProperty('content-type', 'application/pdf');
+    } catch (err) {
+      throw err;
+    }
+  });
+
+  it('GET/example.json (api.get)', async () => {
+    const api = new APIpeline(API_OPTIONS, API_SERVICES);
+    await expect(api.get('getExample')).resolves.toEqual(exampleData);
+  });
+
+  it('GET/example.json (api.fetch)', async () => {
+    const api = new APIpeline(API_OPTIONS, API_SERVICES);
+    await expect(api.fetch('getExample')).resolves.toEqual(exampleData);
+  });
+
+  it('GET/example.json (api.getHeaders)', async () => {
+    const api = new APIpeline(API_OPTIONS, API_SERVICES);
+    expect.assertions(2);
+    try {
+      const headers = await api.fetchHeaders('getExample');
+      expect(headers).toHaveProperty('content-type');
+      expect(headers['content-type']).toEqual('application/json; charset=UTF-8');
+    } catch (err) {
+      throw err;
+    }
+  });
+
+  it('POST/postExample (api.post)', async () => {
+    const api = new APIpeline(API_OPTIONS, API_SERVICES);
+    try {
+      await expect(api.post(
+        'postExample',
+        {
+          fetchOptions: { body: 'key=value' },
+          headers: { 'Content-Type': 'application/x-www-form-urlencoded' }
+        }
+      )).resolves.toEqual({ key: 'value' });
+    } catch (err) {
+      throw err;
+    }
+  });
+});
diff --git a/__tests__/instantiation.test.js b/__tests__/instantiation.test.js
new file mode 100644
index 0000000..143522d
--- /dev/null
+++ b/__tests__/instantiation.test.js
@@ -0,0 +1,33 @@
+import APIpeline from '../dist';
+
+const API_OPTIONS = {
+  fetchMethod: require('whatwg-fetch'),
+  domains: { default: 'http://default.tld' }
+};
+
+const API_SERVICES = {
+  example: { path: 'example' }
+};
+
+describe('>>> Instantiation', () => {
+
+  it('Success with options and services', () => {
+    new APIpeline(API_OPTIONS, API_SERVICES);
+  });
+
+  it('Success without services', () => {
+    new APIpeline(API_OPTIONS);
+  });
+
+  it('Fails when fetchMethod is missing', () => {
+    expect(() => {
+      new APIpeline({ ...API_OPTIONS, fetchMethod: undefined }, API_SERVICES);
+    }).toThrow(/^Your fetch method is undefined/);
+  });
+
+  it('Fails when default domain is missing', () => {
+    expect(() => {
+      new APIpeline({ ...API_OPTIONS, domains: { staging: 'http://staging.myapi.tld' } }, API_SERVICES);
+    }).toThrow(/^You didn't set your default domain URL in your options/);
+  });
+});
diff --git a/__tests__/requirements.test.js b/__tests__/requirements.test.js
new file mode 100644
index 0000000..0badd0d
--- /dev/null
+++ b/__tests__/requirements.test.js
@@ -0,0 +1,12 @@
+import APIpeline from '../dist/index';
+
+const API_OPTIONS = {
+  fetchMethod: require('whatwg-fetch'),
+  domains: { default: 'default' }
+};
+
+describe('>>> Requirements', () => {
+  it('Fetch is polyfilled', () => {
+    new APIpeline(API_OPTIONS);
+  });
+});
diff --git a/__tests__/server.js b/__tests__/server.js
new file mode 100644
index 0000000..8627a3a
--- /dev/null
+++ b/__tests__/server.js
@@ -0,0 +1,19 @@
+const express = require('express');
+const bodyParser = require('body-parser');
+
+const app = express();
+const appRouter = express.Router();
+app.use((req, res, next) => {
+  res.header('Access-Control-Allow-Origin', '*');
+  res.header('Access-Control-Allow-Headers', '*');
+  res.header('Access-Control-Request-Headers', '*');
+  next();
+});
+appRouter.use('/', express.static('__tests__/static'));
+app.use(appRouter);
+appRouter.use(bodyParser.urlencoded({ extended: true }));
+
+appRouter.get('/testHeaders', async (req, res) => res.json(req.headers));
+appRouter.post('/postExample', async (req, res) => res.json(req.body));
+
+export default app;
diff --git a/__tests__/setup.test.js b/__tests__/setup.test.js
new file mode 100644
index 0000000..9950d8a
--- /dev/null
+++ b/__tests__/setup.test.js
@@ -0,0 +1,66 @@
+import APIpeline, { DEFAULT_API_OPTIONS, DEFAULT_SERVICE_OPTIONS } from '../dist';
+
+const API_OPTIONS = {
+  fetchMethod: require('whatwg-fetch'),
+  domains: { default: 'http://default.tld' }
+};
+
+describe('>>> Setup API options and services', () => {
+
+  it('Merges the default API options for missing keys', () => {
+    const api = new APIpeline(API_OPTIONS);
+    expect(api._APIOptions).toStrictEqual({
+      ...DEFAULT_API_OPTIONS,
+      ...API_OPTIONS,
+    });
+  });
+
+  it('Merges the default services options for each service', () => {
+    const SERVICES = { default: { path: '/' }, simpleService: { path: 'simpleService', method: 'POST' } };
+    const api = new APIpeline(API_OPTIONS, SERVICES);
+    expect(api._APIServices).toStrictEqual({
+      default: { ...DEFAULT_SERVICE_OPTIONS, ...SERVICES.default,  },
+      simpleService: { ...DEFAULT_SERVICE_OPTIONS, ...SERVICES.simpleService },
+    });
+  });
+
+  it('Updates API options after instantiation', () => {
+    const api = new APIpeline(API_OPTIONS);
+    const UPDATED_OPTIONS = { printNetworkRequests: true };
+    api.setOptions(UPDATED_OPTIONS);
+    expect(api._APIOptions).toStrictEqual({
+      ...DEFAULT_API_OPTIONS,
+      ...API_OPTIONS,
+      ...UPDATED_OPTIONS
+    });
+  });
+
+  it('Sets up services after instantiation without pre-defined services', () => {
+    const UPDATED_SERVICES = { newService: { path: 'http://myNewService.tld' } };
+    const api = new APIpeline(API_OPTIONS);
+    api.setServices(UPDATED_SERVICES);
+    expect(api._APIServices).toStrictEqual({
+      newService: {
+        ...UPDATED_SERVICES.newService,
+        ...DEFAULT_SERVICE_OPTIONS
+      }
+    });
+  });
+
+  it('Adds a new service after instantiation with pre-defined services', () => {
+    const PRE_DEF_SERVICES = { default: { path: 'http://default.tld' } };
+    const UPDATED_SERVICES = { newService: 'http://myNewService.tld' };
+    const api = new APIpeline(API_OPTIONS, PRE_DEF_SERVICES);
+    api.setServices(UPDATED_SERVICES);
+    expect(api._APIServices).toStrictEqual({
+      default: {
+        ...PRE_DEF_SERVICES.default,
+        ...DEFAULT_SERVICE_OPTIONS
+      },
+      newService: {
+        ...UPDATED_SERVICES.newService,
+        ...DEFAULT_SERVICE_OPTIONS
+      }
+    });
+  });
+});
diff --git a/__tests__/static/example.json b/__tests__/static/example.json
new file mode 100644
index 0000000..77ae496
--- /dev/null
+++ b/__tests__/static/example.json
@@ -0,0 +1,3 @@
+{
+  "test": "ok"
+}
diff --git a/__tests__/unit.test.js b/__tests__/unit.test.js
new file mode 100644
index 0000000..21aa83a
--- /dev/null
+++ b/__tests__/unit.test.js
@@ -0,0 +1,17 @@
+import APIpeline, { HTTP_METHODS } from '../dist';
+
+const API_OPTIONS = {
+  fetchMethod: require('whatwg-fetch'),
+  domains: { default: 'http://default.tld' }
+};
+
+
+describe('>>> Unit tests', () => {
+
+  it('Implements every HTTP methods', () => {
+    const api = new APIpeline(API_OPTIONS);
+    HTTP_METHODS.forEach((method) => {
+      expect(typeof api[method.toLowerCase()]).toBe('function');
+    });
+  })
+});
diff --git a/package.json b/package.json
index 01e303e..f8d4f59 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,13 @@
   "types": "./src/index.d.ts",
   "scripts": {
     "start": "tsc --watch",
-    "test": "echo \"Error: no test specified\" && exit 1"
+    "build": "tsc",
+    "test": "jest --watch --verbose",
+    "test:coverage": "jest --collectCoverage"
+  },
+  "jest": {
+    "testRegex": "(\\/__tests__\\/.*|(\\.|\\/)(test|spec))\\.(test)\\.[jt]sx?$",
+    "collectCoverageFrom": ["dist/**/*.js"]
   },
   "repository": {
     "type": "git",
@@ -37,7 +43,14 @@
   },
   "homepage": "https://github.com/Exilz/apipeline#readme",
   "devDependencies": {
-    "typescript": "^2.4.2"
+    "@babel/core": "^7.4.0",
+    "@babel/preset-env": "^7.4.2",
+    "@types/jest": "^24.0.11",
+    "babel-jest": "^24.5.0",
+    "express": "^4.16.4",
+    "jest": "^24.5.0",
+    "typescript": "^2.4.2",
+    "whatwg-fetch": "^3.0.0"
   },
   "dependencies": {
     "jssha": "^2.3.1",
diff --git a/tsconfig.json b/tsconfig.json
index a71bb14..6817270 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -2,7 +2,7 @@
     "compilerOptions": {
         "target": "es5",
         "baseUrl": "./",
-        "lib": ["es2015"],
+        "lib": ["es2015", "dom"],
         "pretty": true,
         "jsx": "react-native",
         "outDir": "./dist",
@@ -20,6 +20,7 @@
     ],
     "exclude": [
         "node_modules",
-        "demo"
+        "demo",
+        "__tests__"
     ]
-}
\ No newline at end of file
+}