diff --git a/jest/__fixtures__/meta.json b/jest/__fixtures__/meta.json
index 1ad3618..c4704af 100644
--- a/jest/__fixtures__/meta.json
+++ b/jest/__fixtures__/meta.json
@@ -9,6 +9,9 @@
       "childImageSharp": {
         "fluid": {
           "src": "/static/b45f45aa8d98d4e4019a242d38f2f248/bc3a8/avatar.jpg"
+        },
+        "resize": {
+          "src": "/static/b45f45aa8d98d4e4019a242d38f2f248/bc3a8/avatar.jpg"
         }
       }
     },
diff --git a/package.json b/package.json
index 4700725..44e8ef0 100644
--- a/package.json
+++ b/package.json
@@ -18,6 +18,7 @@
     "format": "prettier --write 'src/**/*.{js,jsx}'",
     "format:css": "prettier-stylelint --write --quiet 'src/**/*.{css,scss}'",
     "test": "npm run lint && jest --coverage",
+    "test:watch": "npm run lint && jest --coverage --watch",
     "deploy": "./scripts/deploy.sh",
     "new": "babel-node ./scripts/new.js"
   },
diff --git a/src/components/Layout.jsx b/src/components/Layout.jsx
index 999de04..837bd65 100644
--- a/src/components/Layout.jsx
+++ b/src/components/Layout.jsx
@@ -25,59 +25,62 @@ const query = graphql`
   }
 `
 
-const LayoutMarkup = ({ children, isHomepage, allowedHosts, location }) => (
-  <>
-    <Typekit />
-    <HostnameCheck allowedHosts={allowedHosts} />
+const LayoutMarkup = ({ children, data, location }) => {
+  const { allowedHosts } = data.contentYaml
+  const isHomepage = location.pathname === '/'
 
-    <PoseGroup animateOnMount={true}>
-      <RoutesContainer
-        key={location.pathname}
-        delay={timeout}
-        delayChildren={timeout}
-      >
-        <Header minimal={!isHomepage} />
-        <main className={styles.screen}>{children}</main>
-      </RoutesContainer>
-    </PoseGroup>
+  return (
+    <>
+      <Typekit />
+      <HostnameCheck allowedHosts={allowedHosts} />
 
-    <Footer />
-  </>
-)
+      <PoseGroup animateOnMount={true}>
+        <RoutesContainer
+          key={location.pathname}
+          delay={timeout}
+          delayChildren={timeout}
+        >
+          <Header minimal={!isHomepage} />
+          <main className={styles.screen}>{children}</main>
+        </RoutesContainer>
+      </PoseGroup>
+
+      <Footer />
+    </>
+  )
+}
 
 LayoutMarkup.propTypes = {
   children: PropTypes.any.isRequired,
-  isHomepage: PropTypes.bool.isRequired,
-  allowedHosts: PropTypes.array.isRequired,
-  location: PropTypes.object.isRequired
+  data: PropTypes.shape({
+    contentYaml: PropTypes.shape({
+      allowedHosts: PropTypes.array.isRequired
+    }).isRequired
+  }).isRequired,
+  location: PropTypes.shape({
+    pathname: PropTypes.string.isRequired
+  }).isRequired
 }
 
 export default class Layout extends PureComponent {
   static propTypes = {
     children: PropTypes.any.isRequired,
-    location: PropTypes.object.isRequired
+    location: PropTypes.shape({
+      pathname: PropTypes.string.isRequired
+    }).isRequired
   }
 
   render() {
     const { children, location } = this.props
-    const isHomepage = location.pathname === '/'
 
     return (
       <StaticQuery
         query={query}
-        render={data => {
-          const { allowedHosts } = data.contentYaml
-
-          return (
-            <LayoutMarkup
-              isHomepage={isHomepage}
-              allowedHosts={allowedHosts}
-              location={location}
-            >
-              {children}
-            </LayoutMarkup>
-          )
-        }}
+        render={data => (
+          <LayoutMarkup data={data} location={location}>
+            {children}
+          </LayoutMarkup>
+        )}
       />
     )
   }
diff --git a/src/components/atoms/Vcard.jsx b/src/components/atoms/Vcard.jsx
index ecb57df..6ea6626 100644
--- a/src/components/atoms/Vcard.jsx
+++ b/src/components/atoms/Vcard.jsx
@@ -13,7 +13,7 @@ const query = graphql`
       email
       avatar {
         childImageSharp {
-          original: resize {
+          resize {
             src
           }
         }
@@ -62,15 +62,16 @@ export default class Vcard extends PureComponent {
 
 // Construct the download from a blob of the just constructed vCard,
 // and save it to user's file system
-const downloadVcard = (vcard, meta) => {
-  const name = meta.addressbook.split('/').join('')
+export const downloadVcard = (vcard, meta) => {
+  const { addressbook } = meta
+  const name = addressbook.split('/').join('')
   const blob = new Blob([vcard], { type: 'text/x-vcard' })
   saveAs(blob, name)
 }
 
-const constructVcard = meta => {
+export const constructVcard = meta => {
   const contact = new vCard()
-  const photoSrc = meta.avatar.childImageSharp.original.src
+  const photoSrc = meta.avatar.childImageSharp.resize.src
 
   // first, convert the avatar to base64, then construct all vCard elements
   toDataURL(
@@ -99,7 +100,7 @@ const constructVcard = meta => {
 
 // Helper function to create base64 string from avatar image
 // without the need to read image file from file system
-const toDataURL = (src, callback, outputFormat) => {
+export const toDataURL = (src, callback, outputFormat) => {
   const img = new Image()
   img.crossOrigin = 'Anonymous'
 
@@ -118,6 +119,7 @@ const toDataURL = (src, callback, outputFormat) => {
   }
 
   img.src = src
+
   if (img.complete || img.complete === undefined) {
     img.src =
       'data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///ywAAAAAAQABAAACAUwAOw=='
diff --git a/src/components/atoms/Vcard.test.jsx b/src/components/atoms/Vcard.test.jsx
new file mode 100644
index 0000000..45b42a7
--- /dev/null
+++ b/src/components/atoms/Vcard.test.jsx
@@ -0,0 +1,37 @@
+import React from 'react'
+import { render } from 'react-testing-library'
+import { StaticQuery } from 'gatsby'
+import vCard from 'vcf'
+import Vcard, { constructVcard, downloadVcard, toDataURL } from './Vcard'
+import data from '../../../jest/__fixtures__/meta.json'
+
+describe('Vcard', () => {
+  beforeEach(() => {
+    StaticQuery.mockImplementationOnce(({ render }) => render({ ...data }))
+  })
+
+  it('renders correctly', () => {
+    const { container } = render(<Vcard />)
+
+    expect(container.firstChild).toBeInTheDocument()
+  })
+
+  it('vCard can be constructed', async () => {
+    await constructVcard(data.contentYaml)
+  })
+
+  it('vCard can be downloaded', async () => {
+    const contact = new vCard()
+    const vcard = contact.toString('3.0')
+
+    global.URL.createObjectURL = jest.fn(() => 'details')
+    await downloadVcard(vcard, data.contentYaml)
+    expect(global.URL.createObjectURL).toHaveBeenCalledTimes(1)
+  })
+
+  it('Base64 from image can be constructed', () => {
+    const photoSrc = data.contentYaml.avatar.childImageSharp.resize.src
+
+    toDataURL(photoSrc, () => null, 'image/jpeg')
+  })
+})
diff --git a/src/components/molecules/ThemeSwitch.jsx b/src/components/molecules/ThemeSwitch.jsx
index 8437f5e..1c689ed 100644
--- a/src/components/molecules/ThemeSwitch.jsx
+++ b/src/components/molecules/ThemeSwitch.jsx
@@ -48,7 +48,10 @@ export default class ThemeSwitch extends PureComponent {
             <Helmet>
               <body className={dark ? 'dark' : null} />
             </Helmet>
-            <Animation className={styles.themeSwitch}>
+            <Animation
+              className={styles.themeSwitch}
+              data-testid={'theme-switch'}
+            >
               <label className={styles.checkbox}>
                 <span className={styles.label}>Toggle Night Mode</span>
                 <ThemeToggleInput dark={dark} toggleDark={toggleDark} />
diff --git a/src/components/molecules/ThemeSwitch.test.jsx b/src/components/molecules/ThemeSwitch.test.jsx
new file mode 100644
index 0000000..4ddb029
--- /dev/null
+++ b/src/components/molecules/ThemeSwitch.test.jsx
@@ -0,0 +1,17 @@
+import React from 'react'
+import { render } from 'react-testing-library'
+import AppProvider from '../../store/provider'
+import ThemeSwitch from './ThemeSwitch'
+
+describe('ThemeSwitch', () => {
+  it('renders correctly', () => {
+    const { getByTestId } = render(
+      <AppProvider>
+        <ThemeSwitch />
+      </AppProvider>
+    )
+
+    expect(getByTestId('theme-switch')).toBeInTheDocument()
+    expect(getByTestId('theme-switch').nodeName).toBe('ASIDE')
+  })
+})
diff --git a/src/components/organisms/Footer.jsx b/src/components/organisms/Footer.jsx
index 471eff4..8ec65f8 100644
--- a/src/components/organisms/Footer.jsx
+++ b/src/components/organisms/Footer.jsx
@@ -1,4 +1,5 @@
 import React, { PureComponent } from 'react'
+import PropTypes from 'prop-types'
 import { Link, StaticQuery, graphql } from 'gatsby'
 import classNames from 'classnames'
 import Vcard from '../atoms/Vcard'
@@ -24,12 +25,10 @@ const query = graphql`
   }
 `
 
-let classes = classNames('h-card', [styles.footer])
+export const FooterMarkup = ({ pkg, meta, year }) => {
+  const classes = classNames('h-card', [styles.footer])
 
-export default class Footer extends PureComponent {
-  state = { year: new Date().getFullYear() }
-
-  FooterMarkup = ({ meta, pkg, year }) => (
+  return (
     <footer className={classes}>
       <Link to={'/'}>
         <LogoUnit minimal />
@@ -55,6 +54,16 @@ export default class Footer extends PureComponent {
       </p>
     </footer>
   )
+}
+
+FooterMarkup.propTypes = {
+  pkg: PropTypes.object.isRequired,
+  meta: PropTypes.object.isRequired,
+  year: PropTypes.number.isRequired
+}
+
+export default class Footer extends PureComponent {
+  state = { year: new Date().getFullYear() }
 
   render() {
     return (
@@ -64,9 +73,7 @@ export default class Footer extends PureComponent {
           const pkg = data.portfolioJson
           const meta = data.contentYaml
 
-          return (
-            <this.FooterMarkup year={this.state.year} pkg={pkg} meta={meta} />
-          )
+          return <FooterMarkup year={this.state.year} pkg={pkg} meta={meta} />
         }}
       />
     )
diff --git a/src/store/provider.jsx b/src/store/provider.jsx
index bae29b5..4f5fdfa 100644
--- a/src/store/provider.jsx
+++ b/src/store/provider.jsx
@@ -23,28 +23,26 @@ export default class AppProvider extends PureComponent {
   getCountry = async () => {
     let trace = []
 
-    await fetch('/cdn-cgi/trace?no-cache=1')
-      .then(data => {
-        let lines
+    try {
+      const data = await fetch('/cdn-cgi/trace?no-cache=1')
+      const text = await data.text()
+      const lines = text.split('\n')
 
-        data.text().then(text => {
-          lines = text.split('\n')
+      let keyValue
 
-          let keyValue
+      lines.forEach(line => {
+        keyValue = line.split('=')
+        trace[keyValue[0]] = decodeURIComponent(keyValue[1] || '')
 
-          lines.forEach(line => {
-            keyValue = line.split('=')
-            trace[keyValue[0]] = decodeURIComponent(keyValue[1] || '')
-
-            if (keyValue[0] === 'loc' && trace['loc'] !== 'XX') {
-              this.setState({ location: trace['loc'] })
-            } else {
-              return
-            }
-          })
-        })
+        if (keyValue[0] === 'loc' && trace['loc'] !== 'XX') {
+          this.setState({ location: trace['loc'] })
+        } else {
+          return
+        }
       })
-      .catch(() => null) // fail silently
+    } catch (error) {
+      return null // fail silently
+    }
   }
 
   setDark() {