these too

frontend/src/lib/map-utils.test.ts

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+import { describe, expect, it } from 'vitest';
+
+import { DENSITY_GRADIENT, ENUM_PALETTE, FEATURE_GRADIENT } from './consts';
+import {
+  emojiToTwemojiUrl,
+  enumIndexToColor,
+  getBoundsFromViewState,
+  getFeatureFillColor,
+  zoomToResolution,
+} from './map-utils';
+
+describe('map utilities', () => {
+  it('maps zoom levels to H3 resolutions at configured thresholds', () => {
+    expect(zoomToResolution(6.9)).toBe(5);
+    expect(zoomToResolution(7)).toBe(6);
+    expect(zoomToResolution(10.6)).toBe(8);
+    expect(zoomToResolution(14)).toBe(9);
+  });
+
+  it('computes buffered bounds around a view state', () => {
+    const bounds = getBoundsFromViewState(
+      { latitude: 51.5, longitude: -0.1, zoom: 12, pitch: 0 },
+      1200,
+      800
+    );
+
+    expect(bounds.south).toBeLessThan(51.5);
+    expect(bounds.north).toBeGreaterThan(51.5);
+    expect(bounds.west).toBeLessThan(-0.1);
+    expect(bounds.east).toBeGreaterThan(-0.1);
+  });
+
+  it('builds twemoji URLs and wraps enum colors', () => {
+    expect(emojiToTwemojiUrl('🛒')).toBe('/assets/twemoji/1f6d2.png');
+    expect(emojiToTwemojiUrl('')).toBe('/assets/twemoji/1f4cd.png');
+    expect(enumIndexToColor(ENUM_PALETTE.length)).toEqual(ENUM_PALETTE[0]);
+  });
+
+  it('returns fallback, filtered, enum, feature, and density colors', () => {
+    expect(
+      getFeatureFillColor(
+        null,
+        undefined,
+        undefined,
+        [0, 100],
+        null,
+        0,
+        DENSITY_GRADIENT,
+        false,
+        180
+      )
+    ).toEqual([128, 128, 128, 80]);
+
+    expect(
+      getFeatureFillColor(50, 50, 60, [0, 100], [70, 90], 0, DENSITY_GRADIENT, true, 180)
+    ).toEqual([60, 55, 50, 60]);
+
+    expect(
+      getFeatureFillColor(1, 1, 1, [0, 2], null, 0, DENSITY_GRADIENT, false, 180, 3, ENUM_PALETTE)
+    ).toEqual([...ENUM_PALETTE[1], 180]);
+
+    expect(
+      getFeatureFillColor(
+        0,
+        0,
+        100,
+        [0, 100],
+        null,
+        0,
+        DENSITY_GRADIENT,
+        false,
+        200,
+        0,
+        undefined,
+        FEATURE_GRADIENT
+      )
+    ).toEqual([...FEATURE_GRADIENT[0].color, 200]);
+
+    expect(
+      getFeatureFillColor(
+        undefined,
+        undefined,
+        undefined,
+        null,
+        null,
+        0,
+        DENSITY_GRADIENT,
+        false,
+        150
+      )
+    ).toEqual([...DENSITY_GRADIENT[0].color, 150]);
+  });
+});