feat: add testing library dependencies and implement component tests

src/containers/BerlinClock.tsx

@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { Lamp } from '../components/Lamp';
 import { LampLine } from '../components/LampLine';
 import { useCurrentTime } from '../hooks/useCurrentTime';
 import { dateToBerlin } from '../utils';
@@ -10,6 +11,39 @@ interface BerlinClockProps {
 export function BerlinClock({ enabled }: BerlinClockProps) {
   const { currentTime } = useCurrentTime();
   const berlin = dateToBerlin(currentTime);
-  // Will render four LampLine components
-  return null;
+
+  if (!enabled) return null;
+
+  return (
+    <div>
+      {/* Seconds lamp */}
+      <div data-testid="seconds-lamp">
+        {berlin.secondsRow.length > 0 && (
+          <span data-testid="lamp-0" aria-label={berlin.secondsRow[0]}>
+            {/* optional visual */}
+          </span>
+        )}
+      </div>
+
+      {/* Five hours row */}
+      <div data-testid="five-hours-row">
+        <LampLine states={berlin.fiveHours} />
+      </div>
+
+      {/* Single hours row */}
+      <div data-testid="single-hours-row">
+        <LampLine states={berlin.oneHour} />
+      </div>
+
+      {/* Five minutes row */}
+      <div data-testid="five-minutes-row">
+        <LampLine states={berlin.fiveMinutes} />
+      </div>
+
+      {/* Single minutes row */}
+      <div data-testid="single-minutes-row">
+        <LampLine states={berlin.oneMinute} />
+      </div>
+    </div>
+  );
 }