test: add tooltip utils empty fallback tests

Author: mayank200529

components/dashboard/tooltipUtils.empty-fallback.test.ts

@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest';
+import {
+  formatTooltipDate,
+  getActivityInsight,
+  getContributionLabel,
+  getLocalActiveStreak,
+  getStreakLabel,
+} from './tooltipUtils';
+
+describe('tooltipUtils empty fallback behavior', () => {
+  it('returns original value for empty or invalid tooltip dates', () => {
+    expect(formatTooltipDate('')).toBe('');
+    expect(formatTooltipDate('invalid-date')).toBe('invalid-date');
+  });
+
+  it('formats zero contributions with plural fallback label', () => {
+    expect(getContributionLabel(0)).toBe('0 contributions');
+  });
+
+  it('returns no activity insight for zero count without intensity', () => {
+    expect(getActivityInsight(0)).toBe('No activity recorded');
+  });
+
+  it('returns zero local active streak for empty activity data', () => {
+    expect(getLocalActiveStreak([], 0)).toBe(0);
+  });
+
+  it('returns no active streak label for zero or negative streaks', () => {
+    expect(getStreakLabel(0)).toBe('No active streak');
+    expect(getStreakLabel(-1)).toBe('No active streak');
+  });
+});