diff --git a/source/engine/format.js b/source/engine/format.js
index 75f0086c5..76d836622 100644
--- a/source/engine/format.js
+++ b/source/engine/format.js
@@ -75,7 +75,8 @@ export function formatValue({
 				numberFormatter({
 					style: 'decimal',
 					minimumFractionDigits,
-					maximumFractionDigits
+					maximumFractionDigits,
+					language
 				})(value) +
 				(typeof serializedUnit === 'string' ? `\u00A0${serializedUnit}` : '')
 			)
diff --git a/source/engine/format.test.js b/source/engine/format.test.js
new file mode 100644
index 000000000..577dfeab9
--- /dev/null
+++ b/source/engine/format.test.js
@@ -0,0 +1,27 @@
+import { expect } from 'chai'
+import { formatCurrency, formatPercentage, formatValue } from './format'
+
+describe('format engine values', () => {
+	it('format currencies', () => {
+		expect(formatCurrency(12, 'fr')).to.equal('12 €')
+		expect(formatCurrency(1200, 'fr')).to.equal('1 200 €')
+		expect(formatCurrency(12, 'en')).to.equal('€ 12')
+		expect(formatCurrency(12.1)).to.equal('€ 12.10')
+		expect(formatCurrency(12.123)).to.equal('€ 12.12')
+	})
+
+	it('format percentages', () => {
+		expect(formatPercentage(0.1)).to.equal('10%')
+		expect(formatPercentage(1)).to.equal('100%')
+		expect(formatPercentage(0.102)).to.equal('10.2%')
+	})
+
+	it('format values', () => {
+		expect(formatValue({ unit: '€', value: 12 })).to.equal('€12')
+		expect(formatValue({ unit: '€', value: 12.1 })).to.equal('€12.10')
+		expect(formatValue({ unit: '€', value: 12, language: 'fr' })).to.equal(
+			'12 €'
+		)
+		expect(formatValue({ value: 1200, language: 'fr' })).to.equal('1 200')
+	})
+})