diff --git a/package.json b/package.json
index 8579322d8c..335fd824f6 100644
--- a/package.json
+++ b/package.json
@@ -59,6 +59,7 @@
     "typescript": "*",
     "vite": "^5.2.12",
     "vitest": "^1.6.0",
+    "vitest-mock-extended": "^1.3.1",
     "vue-tsc": "^2.0.19"
   },
   "pnpm": {
diff --git a/packages/design-system/src/styleguide/ColorCircles.vue b/packages/design-system/src/styleguide/ColorCircles.vue
index 81955c319f..a1c2904991 100644
--- a/packages/design-system/src/styleguide/ColorCircles.vue
+++ b/packages/design-system/src/styleguide/ColorCircles.vue
@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { ref, onMounted, onUnmounted, reactive } from 'vue';
+import { ref, onMounted, onUnmounted } from 'vue';
 import type { PropType } from 'vue';
 import { getHex, resolveHSLCalc } from './ColorCircles.utils';
 
@@ -10,23 +10,28 @@ const props = defineProps({
 	},
 });
 
-const hsl = reactive<{ [color: string]: string }>({});
-const observer = ref<MutationObserver | null>(null);
+const getColors = () => {
+	const style = getComputedStyle(document.body);
 
-const setColors = () => {
+	const hslColors: Record<string, string> = {};
 	for (const color of props.colors) {
-		const style = getComputedStyle(document.body);
-		hsl[color] = style.getPropertyValue(color);
+		const colorValue = style.getPropertyValue(color);
+		if (colorValue) {
+			hslColors[color] = colorValue;
+		}
 	}
+
+	return hslColors;
 };
 
-onMounted(() => {
-	setColors();
+const hsl = ref<{ [color: string]: string }>(getColors());
+const observer = ref<MutationObserver | null>(null);
 
+onMounted(() => {
 	observer.value = new MutationObserver((mutationsList) => {
 		for (const mutation of mutationsList) {
 			if (mutation.type === 'attributes') {
-				setColors();
+				hsl.value = getColors();
 			}
 		}
 	});
@@ -42,8 +47,8 @@ onUnmounted(() => {
 });
 
 // Expose functions for template usage
-const getHexValue = (color: string) => getHex(hsl[color]);
-const getHSLValue = (color: string) => resolveHSLCalc(hsl[color]);
+const getHexValue = (color: string) => getHex(hsl.value[color]);
+const getHSLValue = (color: string) => resolveHSLCalc(hsl.value[color]);
 </script>
 
 <template>
diff --git a/packages/design-system/src/styleguide/Sizes.vue b/packages/design-system/src/styleguide/Sizes.vue
index 0bc08afd1c..56d9a345bc 100644
--- a/packages/design-system/src/styleguide/Sizes.vue
+++ b/packages/design-system/src/styleguide/Sizes.vue
@@ -1,6 +1,11 @@
 <script setup lang="ts">
 import type { PropType } from 'vue';
-import { ref, onMounted, onUnmounted, reactive } from 'vue';
+import { ref, onMounted, onUnmounted } from 'vue';
+
+type Size = {
+	rem: string;
+	px: number;
+};
 
 // Define props with their types
 const props = defineProps({
@@ -14,27 +19,29 @@ const props = defineProps({
 	},
 });
 
-const sizes = reactive<Record<string, { rem: string; px: number }>>({});
-const observer = ref<MutationObserver | null>(null);
+const getSizes = () => {
+	const style = getComputedStyle(document.body);
 
-const setSizes = () => {
+	const sizeByVariableName: Record<string, Size> = {};
 	for (const variable of props.variables) {
-		const style = getComputedStyle(document.body);
 		const rem = style.getPropertyValue(variable);
 		const px = parseFloat(rem.replace('rem', '')) * 16; // Assuming default font-size is 16px
 
-		sizes[variable] = { rem, px };
+		sizeByVariableName[variable] = { rem, px };
 	}
+
+	return sizeByVariableName;
 };
 
-onMounted(() => {
-	setSizes();
+const sizes = ref<Record<string, Size>>(getSizes());
+const observer = ref<MutationObserver | null>(null);
 
+onMounted(() => {
 	// Observing attributes changes in body to recompute sizes
 	const mutationObserverCallback = (mutationsList: MutationRecord[]) => {
 		for (const mutation of mutationsList) {
 			if (mutation.type === 'attributes') {
-				setSizes();
+				sizes.value = getSizes();
 			}
 		}
 	};
diff --git a/packages/design-system/src/styleguide/__tests__/ColorCircles.spec.ts b/packages/design-system/src/styleguide/__tests__/ColorCircles.spec.ts
new file mode 100644
index 0000000000..d961fd40e5
--- /dev/null
+++ b/packages/design-system/src/styleguide/__tests__/ColorCircles.spec.ts
@@ -0,0 +1,32 @@
+import { render } from '@testing-library/vue';
+import { mock, mockClear } from 'vitest-mock-extended';
+import ColorCircles from '../ColorCircles.vue';
+
+describe('ColorCircles', () => {
+	const mockCssDeclaration = mock<CSSStyleDeclaration>();
+	window.getComputedStyle = () => mockCssDeclaration;
+
+	beforeEach(() => {
+		mockClear(mockCssDeclaration);
+	});
+
+	it('should render an empty section with empty colors', () => {
+		const wrapper = render(ColorCircles, {
+			props: {
+				colors: [],
+			},
+		});
+		expect(wrapper.html()).toMatchSnapshot();
+	});
+
+	it('should render a section with two colors', () => {
+		mockCssDeclaration.getPropertyValue.mockReturnValue('#663399');
+
+		const wrapper = render(ColorCircles, {
+			props: {
+				colors: ['--color-primary-shade-1', '--color-primary'],
+			},
+		});
+		expect(wrapper.html()).toMatchSnapshot();
+	});
+});
diff --git a/packages/design-system/src/styleguide/__tests__/Sizes.spec.ts b/packages/design-system/src/styleguide/__tests__/Sizes.spec.ts
new file mode 100644
index 0000000000..3ae44c8757
--- /dev/null
+++ b/packages/design-system/src/styleguide/__tests__/Sizes.spec.ts
@@ -0,0 +1,23 @@
+import { render } from '@testing-library/vue';
+import { mock, mockClear } from 'vitest-mock-extended';
+import Sizes from '../Sizes.vue';
+
+describe('Sizes', () => {
+	const mockCssDeclaration = mock<CSSStyleDeclaration>();
+	window.getComputedStyle = () => mockCssDeclaration;
+
+	beforeEach(() => {
+		mockClear(mockCssDeclaration);
+	});
+
+	it('should render a section with a variable', () => {
+		mockCssDeclaration.getPropertyValue.mockReturnValue('400');
+
+		const wrapper = render(Sizes, {
+			props: {
+				variables: ['--font-weight-regular'],
+			},
+		});
+		expect(wrapper.html()).toMatchSnapshot();
+	});
+});
diff --git a/packages/design-system/src/styleguide/__tests__/__snapshots__/ColorCircles.spec.ts.snap b/packages/design-system/src/styleguide/__tests__/__snapshots__/ColorCircles.spec.ts.snap
new file mode 100644
index 0000000000..06ea288616
--- /dev/null
+++ b/packages/design-system/src/styleguide/__tests__/__snapshots__/ColorCircles.spec.ts.snap
@@ -0,0 +1,14 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`ColorCircles > should render a section with two colors 1`] = `
+"<div class="section">
+  <div class="container">
+    <div class="circle"></div><span>--color-primary-shade-1</span><span class="hsl">#663399</span><span class="color">#NaNNaNNaN</span>
+  </div>
+  <div class="container">
+    <div class="circle"></div><span>--color-primary</span><span class="hsl">#663399</span><span class="color">#NaNNaNNaN</span>
+  </div>
+</div>"
+`;
+
+exports[`ColorCircles > should render an empty section with empty colors 1`] = `"<div class="section"></div>"`;
diff --git a/packages/design-system/src/styleguide/__tests__/__snapshots__/Sizes.spec.ts.snap b/packages/design-system/src/styleguide/__tests__/__snapshots__/Sizes.spec.ts.snap
new file mode 100644
index 0000000000..52551ea761
--- /dev/null
+++ b/packages/design-system/src/styleguide/__tests__/__snapshots__/Sizes.spec.ts.snap
@@ -0,0 +1,16 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`Sizes > should render a section with a variable 1`] = `
+"<table class="table">
+  <tr>
+    <th class="row">Name</th>
+    <th class="row">rem</th>
+    <th class="row">px</th>
+  </tr>
+  <tr>
+    <td>--font-weight-regular</td>
+    <td>400</td>
+    <td>6400</td>
+  </tr>
+</table>"
+`;
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 5437ffad47..249f549b12 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -110,6 +110,9 @@ importers:
       vitest:
         specifier: ^1.6.0
         version: 1.6.0(@types/node@18.16.16)(jsdom@23.0.1)(sass@1.64.1)(terser@5.16.1)
+      vitest-mock-extended:
+        specifier: ^1.3.1
+        version: 1.3.1(typescript@5.4.2)(vitest@1.6.0(@types/node@18.16.16)(jsdom@23.0.1)(sass@1.64.1)(terser@5.16.1))
       vue-tsc:
         specifier: ^2.0.19
         version: 2.0.19(typescript@5.4.2)
@@ -12760,6 +12763,14 @@ packages:
     peerDependencies:
       typescript: ^5.4.2
 
+  ts-essentials@9.4.2:
+    resolution: {integrity: sha512-mB/cDhOvD7pg3YCLk2rOtejHjjdSi9in/IBYE13S+8WA5FBSraYf4V/ws55uvs0IvQ/l0wBOlXy5yBNZ9Bl8ZQ==}
+    peerDependencies:
+      typescript: ^5.4.2
+    peerDependenciesMeta:
+      typescript:
+        optional: true
+
   ts-ics@1.2.2:
     resolution: {integrity: sha512-L7T5JQi99qQ2Uv7AoCHUZ8Mx1bJYo7qBZtBckuHueR90I3WVdW5NC/tOqTVgu18c3zj08du+xlgWlTIcE+Foxw==}
     peerDependencies:
@@ -13245,6 +13256,12 @@ packages:
       terser:
         optional: true
 
+  vitest-mock-extended@1.3.1:
+    resolution: {integrity: sha512-OpghYjh4BDuQ/Mzs3lFMQ1QRk9D8/2O9T47MLUA5eLn7K4RWIy+MfIivYOWEyxjTENjsBnzgMihDjyNalN/K0Q==}
+    peerDependencies:
+      typescript: ^5.4.2
+      vitest: '>=0.31.1'
+
   vitest@1.6.0:
     resolution: {integrity: sha512-H5r/dN06swuFnzNFhq/dnz37bPXnq8xB2xB5JOVk8K09rUtoeNN+LHWkoQ0A/i3hvbUKKcCei9KpbxqHMLhLLA==}
     engines: {node: ^18.0.0 || >=20.0.0}
@@ -27877,6 +27894,10 @@ snapshots:
     dependencies:
       typescript: 5.4.2
 
+  ts-essentials@9.4.2(typescript@5.4.2):
+    optionalDependencies:
+      typescript: 5.4.2
+
   ts-ics@1.2.2(date-fns@2.30.0)(lodash@4.17.21)(zod@3.23.8):
     dependencies:
       date-fns: 2.30.0
@@ -28372,6 +28393,12 @@ snapshots:
       sass: 1.64.1
       terser: 5.16.1
 
+  vitest-mock-extended@1.3.1(typescript@5.4.2)(vitest@1.6.0(@types/node@18.16.16)(jsdom@23.0.1)(sass@1.64.1)(terser@5.16.1)):
+    dependencies:
+      ts-essentials: 9.4.2(typescript@5.4.2)
+      typescript: 5.4.2
+      vitest: 1.6.0(@types/node@18.16.16)(jsdom@23.0.1)(sass@1.64.1)(terser@5.16.1)
+
   vitest@1.6.0(@types/node@18.16.16)(jsdom@23.0.1)(sass@1.64.1)(terser@5.16.1):
     dependencies:
       '@vitest/expect': 1.6.0