diff --git a/tests/unit/utils/font-size.spec.js b/tests/unit/utils/font-size.spec.js
new file mode 100644
index 0000000000..ea98b45610
--- /dev/null
+++ b/tests/unit/utils/font-size.spec.js
@@ -0,0 +1,62 @@
+import { expect } from 'chai'
+import sinon from 'sinon'
+import * as fontSize from '@/utils/font-size'
+
+if (!global.localStorage) {
+  global.localStorage = {
+    getItem () { return '{}' },
+    setItem () {}
+  }
+}
+
+describe('Font Size', () => {
+  // Vuetify won't have initialized the value, as there is no DOM and nothing was loaded
+  const TESTING_INITIAL_VALUE = 16
+  let stub = null
+  beforeEach(() => {
+    // Create a dummy HTML html element, as that's not present in JSDOM by default.
+    // Also set the initial value (again, Vuetify won't have set this value yet).
+    const htmlElement = document.createElement('html')
+    htmlElement.style.fontSize = `${TESTING_INITIAL_VALUE}px`
+    const htmlCollection = [htmlElement]
+    stub = sinon.stub(document, 'getElementsByTagName').returns(htmlCollection)
+    // Reset the localStorage value
+    delete global.localStorage.fontSize
+  })
+  afterEach(() => {
+    if (stub !== null) {
+      // Undo mocking
+      stub.restore()
+    }
+  })
+  it('Should calculate expected font size correctly', () => {
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.expectedFontSize(true, 0, TESTING_INITIAL_VALUE))
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.expectedFontSize(false, 0, TESTING_INITIAL_VALUE))
+    expect(TESTING_INITIAL_VALUE * 1.2).to.be.equal(fontSize.expectedFontSize(true, 1, TESTING_INITIAL_VALUE))
+    expect(TESTING_INITIAL_VALUE * 1.2 * 1.2).to.be.equal(fontSize.expectedFontSize(true, 2, TESTING_INITIAL_VALUE))
+    expect(TESTING_INITIAL_VALUE * 0.8).to.be.equal(fontSize.expectedFontSize(false, 1, TESTING_INITIAL_VALUE))
+    expect(TESTING_INITIAL_VALUE * 0.8 * 0.8).to.be.equal(fontSize.expectedFontSize(false, 2, TESTING_INITIAL_VALUE))
+  })
+  it('Should return the correct current font size', () => {
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.getCurrentFontSize())
+  })
+  it('Should increase the font size correctly', () => {
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.getCurrentFontSize())
+    fontSize.increaseFontSize()
+    fontSize.increaseFontSize()
+    expect(TESTING_INITIAL_VALUE * 1.2 * 1.2).to.be.equal(fontSize.expectedFontSize(true, 2, TESTING_INITIAL_VALUE))
+  })
+  it('Should decrease the font size correctly', () => {
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.getCurrentFontSize())
+    fontSize.decreaseFontSize()
+    fontSize.decreaseFontSize()
+    expect(TESTING_INITIAL_VALUE * 0.8 * 0.8).to.be.equal(fontSize.expectedFontSize(false, 2, TESTING_INITIAL_VALUE))
+  })
+  it('Should reset the font size correctly', () => {
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.getCurrentFontSize())
+    fontSize.decreaseFontSize()
+    fontSize.decreaseFontSize()
+    fontSize.resetFontSize(`${TESTING_INITIAL_VALUE}px`)
+    expect(TESTING_INITIAL_VALUE).to.be.equal(fontSize.getCurrentFontSize())
+  })
+})