diff --git a/.circleci/config.yml b/.circleci/config.yml
index 2d36678..150755d 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -19,4 +19,7 @@ jobs:
           key: v1-dependencies-{{ checksum "package.json" }}
       - run:
           name: Run Test
-          command: yarn test
\ No newline at end of file
+          command: yarn test
+      - run:
+          name: Build the app
+          command: yarn build
\ No newline at end of file
diff --git a/README.md b/README.md
index e34eb16..4c7bb3b 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 ## React features 🤓
 
+[![CircleCI](https://circleci.com/gh/Will956/react-features/tree/master.svg?style=svg)](https://circleci.com/gh/Will956/react-features/tree/master)
+
 I usually use this repo in order to test new React features.
 
 ## Features
diff --git a/package.json b/package.json
index fb1c34d..32711db 100644
--- a/package.json
+++ b/package.json
@@ -61,7 +61,9 @@
   },
   "eslintConfig": {
     "extends": "react-app",
-    "plugins": ["react-hooks"],
+    "plugins": [
+      "react-hooks"
+    ],
     "rules": {
       "react-hooks/rules-of-hooks": "error"
     }
@@ -119,6 +121,7 @@
     ]
   },
   "devDependencies": {
-    "eslint-plugin-react-hooks": "^1.0.1"
+    "eslint-plugin-react-hooks": "^1.0.1",
+    "react-testing-library": "^5.5.3"
   }
 }
diff --git a/src/components/Hooks/BasicHooks/index.js b/src/components/Hooks/BasicHooks/index.js
new file mode 100644
index 0000000..ba44c57
--- /dev/null
+++ b/src/components/Hooks/BasicHooks/index.js
@@ -0,0 +1,15 @@
+import React, { useState } from 'react';
+
+const BasicHooks = () => {
+  const [count, setCount] = useState(0);
+
+  return (
+    <>
+      <button id="add" onClick={() => setCount(count + 1)}>Add one more</button>
+      <button id="remove" onClick={() => setCount(count - 1)}>Remove one more</button>
+      <p>Counter: {count}</p>
+    </>
+  )
+};
+
+export default BasicHooks;
diff --git a/src/components/Hooks/BasicHooks/index.test.js b/src/components/Hooks/BasicHooks/index.test.js
new file mode 100644
index 0000000..ba32a3f
--- /dev/null
+++ b/src/components/Hooks/BasicHooks/index.test.js
@@ -0,0 +1,32 @@
+import React from 'react';
+import { cleanup, fireEvent, render } from 'react-testing-library';
+import BasicHooks from './index';
+
+afterEach(cleanup);
+
+describe('BasicHooks', () => {
+  let counter;
+  let addBtn;
+  let removeBtn;
+
+  beforeEach(() => {
+    const { container, getByText } = render(<BasicHooks />);
+    counter = container.querySelector('p');
+    addBtn = getByText('Add one more');
+    removeBtn = getByText('Remove one more');
+  });
+
+  it('renders BasicHooks', () => {
+    expect(counter.textContent).toBe('Counter: 0');
+  });
+
+  it('update BasicHooks counter', () => {
+    fireEvent.click(addBtn);
+    expect(counter.textContent).toBe('Counter: 1');
+  });
+
+  it('update BasicHooks counter', () => {
+    fireEvent.click(removeBtn);
+    expect(counter.textContent).toBe('Counter: -1');
+  });
+});
\ No newline at end of file
diff --git a/src/components/Hooks/ContextHooks/index.js b/src/components/Hooks/ContextHooks/index.js
new file mode 100644
index 0000000..ce362ef
--- /dev/null
+++ b/src/components/Hooks/ContextHooks/index.js
@@ -0,0 +1,11 @@
+import React, { useContext } from 'react';
+
+import { ThemeContext } from '../../../containers/Playground';
+
+const ContextHooks = () => {
+  const theme = useContext(ThemeContext);
+
+  return <><p>Theme is: {theme}</p></>;
+};
+
+export default ContextHooks;
diff --git a/src/components/Hooks/ContextHooks/index.test.js b/src/components/Hooks/ContextHooks/index.test.js
new file mode 100644
index 0000000..34e8664
--- /dev/null
+++ b/src/components/Hooks/ContextHooks/index.test.js
@@ -0,0 +1,13 @@
+import React from 'react';
+import { cleanup, render } from 'react-testing-library';
+import ContextHooks from './index';
+import { ThemeContext } from '../../../containers/Playground';
+
+afterEach(cleanup);
+
+describe('ContextHooks', () => {
+  it('renders EffectHooks and should have blue as theme', () => {
+    const { container } = render(<ThemeContext.Provider value="random color"><ContextHooks /></ThemeContext.Provider>);
+    expect(container.querySelector('p').textContent).toBe('Theme is: random color');
+  });
+});
\ No newline at end of file
diff --git a/src/components/Hooks/EffectHooks/index.js b/src/components/Hooks/EffectHooks/index.js
new file mode 100644
index 0000000..eb63deb
--- /dev/null
+++ b/src/components/Hooks/EffectHooks/index.js
@@ -0,0 +1,22 @@
+import React, { useState, useEffect } from 'react';
+
+const EffectHooks = () => {
+  const [count, setCount] = useState(0);
+  const [status, setStatus] = useState(null);
+
+  useEffect(() => {
+    setStatus(`Component mounted/updated with ${count}`);
+    return () => console.log('[EffectHooks] Component was unmounted');
+  }, [count]); // only re-run if count changes 🤓
+
+  return (
+    <>
+      <button id="add" onClick={() => setCount(count + 1)}>Add one more</button>
+      <button id="remove" onClick={() => setCount(count - 1)}>Remove one more</button>
+      <p data-testid="counter">Counter: {count}</p>
+      {status && <p data-testid="status">{status}</p>}
+    </>
+  );
+};
+
+export default EffectHooks;
diff --git a/src/components/Hooks/EffectHooks/index.test.js b/src/components/Hooks/EffectHooks/index.test.js
new file mode 100644
index 0000000..04b6fb9
--- /dev/null
+++ b/src/components/Hooks/EffectHooks/index.test.js
@@ -0,0 +1,31 @@
+import React from 'react';
+import { cleanup, fireEvent, render } from 'react-testing-library';
+import EffectHooks from './index';
+
+global.console = {
+  log: jest.fn()
+};
+
+afterEach(cleanup);
+
+describe('BasicHooks', () => {
+  it('renders EffectHooks', () => {
+    const { getByTestId } = render(<EffectHooks />);
+    expect(getByTestId('counter').textContent).toBe('Counter: 0');
+    expect(getByTestId('status').textContent).toBe('Component mounted/updated with 0');
+  });
+
+  it('update status when component did update', () => {
+    const { getByTestId, getByText } = render(<EffectHooks />);
+    const addBtn = getByText('Add one more');
+    fireEvent.click(addBtn);
+    expect(getByTestId('status').textContent).toBe('Component mounted/updated with 1');
+  });
+
+  it('trigger console.log when component did unmount', () => {
+    const { getByText } = render(<EffectHooks />);
+    const addBtn = getByText('Add one more');
+    fireEvent.click(addBtn);
+    expect(console.log).toHaveBeenCalledWith('[EffectHooks] Component was unmounted');
+  });
+});
\ No newline at end of file
diff --git a/src/components/Hooks/ReducerHooks/index.js b/src/components/Hooks/ReducerHooks/index.js
new file mode 100644
index 0000000..e40dcc4
--- /dev/null
+++ b/src/components/Hooks/ReducerHooks/index.js
@@ -0,0 +1,39 @@
+import React, { useReducer } from 'react';
+
+const initialState = {
+  count: 0,
+  previous: 0
+};
+
+const reducer = (state, action) => {
+  switch (action.type) {
+    case 'INCREMENT':
+      return {
+        count: state.count + 1,
+        previous: state.count
+      };
+    case 'DECREMENT':
+      return {
+        count: state.count -1,
+        previous: state.count,
+      }
+
+    default:
+      return state;  
+  }
+};
+
+const ReducerHooks = () => {
+  const [{ count, previous }, dispatch] = useReducer(reducer, initialState);
+
+  return (
+    <>
+      <button id="add" onClick={() => dispatch({ type: 'INCREMENT' })}>Add one more</button>
+      <button id="remove" onClick={() => dispatch({ type: 'DECREMENT' })}>Remove one more</button>
+      <p>Count is: {count}</p>
+      <p>Previous was: {previous}</p>
+    </>
+  );
+};
+
+export default ReducerHooks;
diff --git a/src/components/Hooks/ReducerHooks/index.test.js b/src/components/Hooks/ReducerHooks/index.test.js
new file mode 100644
index 0000000..ef35624
--- /dev/null
+++ b/src/components/Hooks/ReducerHooks/index.test.js
@@ -0,0 +1,25 @@
+import React from 'react';
+import { cleanup, fireEvent, render } from 'react-testing-library';
+import ReducerHooks from './index';
+
+//TODO: Add more tests (ie. test is fn called..)
+
+afterEach(cleanup);
+
+describe('ReducerHooks', () => {
+  it('renders ReducerHooks', () => {
+    const { container } = render(<ReducerHooks />);
+    expect(container.querySelectorAll('p')[0].textContent).toBe('Count is: 0');
+    expect(container.querySelectorAll('p')[1].textContent).toBe('Previous was: 0');
+  });
+
+  it('update ReducerHooks counter', () => {
+    const { container, getByText } = render(<ReducerHooks />);
+
+    const addBtn = getByText('Add one more');
+    fireEvent.click(addBtn);
+
+    expect(container.querySelectorAll('p')[0].textContent).toBe('Count is: 1');
+    expect(container.querySelectorAll('p')[1].textContent).toBe('Previous was: 0');
+  });
+});
\ No newline at end of file
diff --git a/src/containers/Playground/index.js b/src/containers/Playground/index.js
index f804090..0287fe2 100644
--- a/src/containers/Playground/index.js
+++ b/src/containers/Playground/index.js
@@ -1,14 +1,35 @@
-import React, { Component } from 'react';
+import React, { createContext } from 'react';
+
+import BasicHooks from '../../components/Hooks/BasicHooks';
+import EffectHooks from '../../components/Hooks/EffectHooks';
+import ContextHooks from '../../components/Hooks/ContextHooks';
+import ReducerHooks from '../../components/Hooks/ReducerHooks';
+
 import './index.scss';
 
-class Playground extends Component {
-  render() {
-    return (
-      <header className="App-header">
-        <p>Edit <code>src/App.js</code> and save to reload.</p>
-      </header>
-    );
-  }
-}
+export const ThemeContext = createContext();
+
+const Playground = () => (
+  <ThemeContext.Provider value="blue">
+    <header className="app-header">
+      <div className="app-block">
+        <p>BasicHooks:</p>
+        <BasicHooks />
+      </div>
+      <div className="app-block">
+        <p>EffectHooks:</p>
+        <EffectHooks />
+      </div>
+      <div className="app-block">
+        <p>ContextHooks:</p>
+        <ContextHooks />
+      </div>
+      <div className="app-block">
+        <p>ReducerHooks:</p>
+        <ReducerHooks />
+      </div>
+    </header>
+  </ThemeContext.Provider>
+);
 
 export default Playground;
diff --git a/src/containers/Playground/index.scss b/src/containers/Playground/index.scss
index 924df6c..725f624 100644
--- a/src/containers/Playground/index.scss
+++ b/src/containers/Playground/index.scss
@@ -1,4 +1,4 @@
-.App-header {
+.app-header {
   background-color: #282c34;
   min-height: 100vh;
   display: flex;
@@ -8,3 +8,10 @@
   font-size: calc(10px + 2vmin);
   color: white;
 }
+
+.app-block {
+  padding: 30px 30px;
+  margin: 10px 0;
+  text-align: center;
+  border: 1px solid white;
+}
diff --git a/yarn.lock b/yarn.lock
index 35e9ac9..ae28b53 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -834,6 +834,13 @@
   dependencies:
     regenerator-runtime "^0.12.0"
 
+"@babel/runtime@^7.1.5", "@babel/runtime@^7.3.1":
+  version "7.3.1"
+  resolved "https://registry.yarnpkg.com/@babel/runtime/-/runtime-7.3.1.tgz#574b03e8e8a9898eaf4a872a92ea20b7846f6f2a"
+  integrity sha512-7jGW8ppV0ant637pIqAcFfQDDH1orEPGJb8aXfUozuCU3QqX7rX4DA8iwrbPrR1hcH0FTTHz47yQnk+bl5xHQA==
+  dependencies:
+    regenerator-runtime "^0.12.0"
+
 "@babel/template@^7.1.0", "@babel/template@^7.1.2", "@babel/template@^7.2.2":
   version "7.2.2"
   resolved "https://registry.yarnpkg.com/@babel/template/-/template-7.2.2.tgz#005b3fdf0ed96e88041330379e0da9a708eb2907"
@@ -885,6 +892,11 @@
   resolved "https://registry.yarnpkg.com/@nodelib/fs.stat/-/fs.stat-1.1.3.tgz#2b5a3ab3f918cca48a8c754c08168e3f03eba61b"
   integrity sha512-shAmDyaQC4H92APFoIaVDHCx5bStIocgvbwQyxPRrbUY20V1EYTbSDchWbuwlMG3V17cprZhA6+78JfB+3DTPw==
 
+"@sheerun/mutationobserver-shim@^0.3.2":
+  version "0.3.2"
+  resolved "https://registry.yarnpkg.com/@sheerun/mutationobserver-shim/-/mutationobserver-shim-0.3.2.tgz#8013f2af54a2b7d735f71560ff360d3a8176a87b"
+  integrity sha512-vTCdPp/T/Q3oSqwHmZ5Kpa9oI7iLtGl3RQaA/NyLHikvcrPxACkkKVr/XzkSPJWXHRhKGzVvb0urJsbMlRxi1Q==
+
 "@svgr/core@^2.4.1":
   version "2.4.1"
   resolved "https://registry.yarnpkg.com/@svgr/core/-/core-2.4.1.tgz#03a407c28c4a1d84305ae95021e8eabfda8fa731"
@@ -3121,6 +3133,16 @@ dom-serializer@0:
     domelementtype "~1.1.1"
     entities "~1.1.1"
 
+dom-testing-library@^3.13.1:
+  version "3.16.5"
+  resolved "https://registry.yarnpkg.com/dom-testing-library/-/dom-testing-library-3.16.5.tgz#8c71f127c6b4ee48115660798040291b59dfc894"
+  integrity sha512-t3OaTcDdsAqtAZNeZ13KnOJmt+2HaDJqYWyf0iBRzbG6GwrNtpF0122Ygu/qkerIwcnHMX1ihwZVx/DhaLpmTw==
+  dependencies:
+    "@babel/runtime" "^7.1.5"
+    "@sheerun/mutationobserver-shim" "^0.3.2"
+    pretty-format "^24.0.0"
+    wait-for-expect "^1.1.0"
+
 domain-browser@^1.1.1:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/domain-browser/-/domain-browser-1.2.0.tgz#3d31f50191a6749dd1375a7f522e823d42e54eda"
@@ -7881,6 +7903,14 @@ pretty-format@^23.6.0:
     ansi-regex "^3.0.0"
     ansi-styles "^3.2.0"
 
+pretty-format@^24.0.0:
+  version "24.0.0"
+  resolved "https://registry.yarnpkg.com/pretty-format/-/pretty-format-24.0.0.tgz#cb6599fd73ac088e37ed682f61291e4678f48591"
+  integrity sha512-LszZaKG665djUcqg5ZQq+XzezHLKrxsA86ZABTozp+oNhkdqa+tG2dX4qa6ERl5c/sRDrAa3lHmwnvKoP+OG/g==
+  dependencies:
+    ansi-regex "^4.0.0"
+    ansi-styles "^3.2.0"
+
 private@^0.1.6, private@^0.1.8:
   version "0.1.8"
   resolved "https://registry.yarnpkg.com/private/-/private-0.1.8.tgz#2381edb3689f7a53d653190060fcf822d2f368ff"
@@ -8141,6 +8171,14 @@ react-error-overlay@^5.1.0:
   resolved "https://registry.yarnpkg.com/react-error-overlay/-/react-error-overlay-5.1.2.tgz#888957b884d4b25b083a82ad550f7aad96585394"
   integrity sha512-7kEBKwU9R8fKnZJBRa5RSIfay4KJwnYvKB6gODGicUmDSAhQJ7Tdnll5S0RLtYrzRfMVXlqYw61rzrSpP4ThLQ==
 
+react-testing-library@^5.5.3:
+  version "5.5.3"
+  resolved "https://registry.yarnpkg.com/react-testing-library/-/react-testing-library-5.5.3.tgz#cfd32da95b29e475003df4f66bd96e34eb5624bd"
+  integrity sha512-67jMsSJHbbm9M0NWvEzjNikDAKRdxivhP6vnpa9xPg/fYh19zkE4rMsFh5YWLpyoomm+e49fg+ubcXaEBYartA==
+  dependencies:
+    "@babel/runtime" "^7.3.1"
+    dom-testing-library "^3.13.1"
+
 react@^16.8.0:
   version "16.8.1"
   resolved "https://registry.yarnpkg.com/react/-/react-16.8.1.tgz#ae11831f6cb2a05d58603a976afc8a558e852c4a"
@@ -9837,6 +9875,11 @@ w3c-xmlserializer@^1.0.1:
     webidl-conversions "^4.0.2"
     xml-name-validator "^3.0.0"
 
+wait-for-expect@^1.1.0:
+  version "1.1.0"
+  resolved "https://registry.yarnpkg.com/wait-for-expect/-/wait-for-expect-1.1.0.tgz#6607375c3f79d32add35cd2c87ce13f351a3d453"
+  integrity sha512-vQDokqxyMyknfX3luCDn16bSaRcOyH6gGuUXMIbxBLeTo6nWuEWYqMTT9a+44FmW8c2m6TRWBdNvBBjA1hwEKg==
+
 walker@~1.0.5:
   version "1.0.7"
   resolved "https://registry.yarnpkg.com/walker/-/walker-1.0.7.tgz#2f7f9b8fd10d677262b18a884e28d19618e028fb"