diff --git a/presenter/src/locales/index.test.ts b/presenter/src/locales/index.test.ts
new file mode 100644
index 0000000000..f68c50cc33
--- /dev/null
+++ b/presenter/src/locales/index.test.ts
@@ -0,0 +1,57 @@
+import { describe, expect, it } from 'vitest'
+
+import { extractLocale } from '.'
+
+describe('extractLocale', () => {
+  describe('on index page', () => {
+    it('has no locale in URL', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/')
+      expect(locale).toBe('de')
+      expect(urlWithoutLocale).toBe('/')
+    })
+
+    it('has no locale in URL and is on section #about', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/#about')
+      expect(locale).toBe('de')
+      expect(urlWithoutLocale).toBe('/#about')
+    })
+
+    it('has a locale in URL', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/en/')
+      expect(locale).toBe('en')
+      expect(urlWithoutLocale).toBe('/')
+    })
+
+    it('has a locale in URL and is on #about section', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/en/#about')
+      expect(locale).toBe('en')
+      expect(urlWithoutLocale).toBe('/#about')
+    })
+  })
+
+  describe('on impressum page', () => {
+    it('has no locale in URL', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/impressum')
+      expect(locale).toBe('de')
+      expect(urlWithoutLocale).toBe('/impressum')
+    })
+
+    it('has no locale in URL and is on section #about', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/impressum#about')
+      expect(locale).toBe('de')
+      expect(urlWithoutLocale).toBe('/impressum#about')
+    })
+
+    it('has a locale in URL', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/en/impressum')
+      expect(locale).toBe('en')
+      expect(urlWithoutLocale).toBe('/impressum')
+    })
+
+    it('has a locale in URL and is on #about section', () => {
+      const { locale, urlWithoutLocale } = extractLocale('/en/impressum#about')
+      expect(locale).toBe('en')
+      expect(urlWithoutLocale).toBe('/impressum#about')
+    })
+  })
+})