diff --git a/frontend/src/__tests__/polishFeatures.test.js b/frontend/src/__tests__/polishFeatures.test.js
new file mode 100644
index 0000000..05e4a04
--- /dev/null
+++ b/frontend/src/__tests__/polishFeatures.test.js
@@ -0,0 +1,126 @@
+import { describe, it, expect } from 'vitest'
+import { EDITOR_ONLY_TAGS } from '../stores/recipes'
+
+// ---------------------------------------------------------------------------
+// Tag sorting
+// ---------------------------------------------------------------------------
+describe('Tag sorting', () => {
+  it('sorts tags alphabetically with localeCompare zh', () => {
+    const tags = ['香水', '呼吸', '消化', '美容']
+    const sorted = [...tags].sort((a, b) => a.localeCompare(b, 'zh'))
+    expect(sorted[0]).toBe('呼吸')
+    // All sorted
+    for (let i = 1; i < sorted.length; i++) {
+      expect(sorted[i - 1].localeCompare(sorted[i], 'zh')).toBeLessThanOrEqual(0)
+    }
+  })
+
+  it('EDITOR_ONLY_TAGS filters correctly', () => {
+    const allTags = ['呼吸', '已审核', '消化', '香水']
+    const visible = allTags.filter(t => !EDITOR_ONLY_TAGS.includes(t))
+    expect(visible).not.toContain('已审核')
+    expect(visible).toContain('呼吸')
+    expect(visible).toHaveLength(3)
+  })
+})
+
+// ---------------------------------------------------------------------------
+// Recipe save data format
+// ---------------------------------------------------------------------------
+describe('Recipe data format', () => {
+  it('oil_name format overwrites oil format when spread', () => {
+    // This test documents the bug that was fixed
+    const localRecipe = {
+      ingredients: [{ oil: '薰衣草', drops: 3 }],
+    }
+    const payload = {
+      ingredients: [{ oil_name: '薰衣草', drops: 3 }],
+    }
+    const merged = { ...localRecipe, ...payload }
+    // After merge, ingredients have oil_name not oil — this was the bug
+    expect(merged.ingredients[0]).toHaveProperty('oil_name')
+    expect(merged.ingredients[0]).not.toHaveProperty('oil')
+  })
+
+  it('loadRecipes mapping converts oil_name to oil', () => {
+    // Simulate what loadRecipes does
+    const apiData = [
+      { id: 1, name: 'test', ingredients: [{ oil_name: '薰衣草', drops: 3 }], tags: [] }
+    ]
+    const mapped = apiData.map(r => ({
+      ...r,
+      ingredients: r.ingredients.map(ing => ({
+        oil: ing.oil_name ?? ing.oil,
+        drops: ing.drops,
+      }))
+    }))
+    expect(mapped[0].ingredients[0].oil).toBe('薰衣草')
+    expect(mapped[0].ingredients[0]).not.toHaveProperty('oil_name')
+  })
+})
+
+// ---------------------------------------------------------------------------
+// Volume detection from ingredients
+// ---------------------------------------------------------------------------
+describe('Volume detection', () => {
+  const DROPS_PER_ML = 18.6
+
+  function guessVolume(eoDrops, cocoDrops) {
+    const totalDrops = eoDrops + cocoDrops
+    const ml = totalDrops / DROPS_PER_ML
+    if (ml <= 2) return 'single'
+    if (Math.abs(ml - 5) < 1.5) return '5'
+    if (Math.abs(ml - 10) < 2.5) return '10'
+    if (Math.abs(ml - 15) < 2.5) return '15'
+    if (Math.abs(ml - 20) < 3) return '20'
+    if (Math.abs(ml - 30) < 6) return '30'
+    return 'custom'
+  }
+
+  it('detects single use (small amounts)', () => {
+    expect(guessVolume(5, 10)).toBe('single')
+  })
+
+  it('detects 5ml', () => {
+    expect(guessVolume(15, Math.round(5 * DROPS_PER_ML) - 15)).toBe('5')
+  })
+
+  it('detects 10ml', () => {
+    expect(guessVolume(20, Math.round(10 * DROPS_PER_ML) - 20)).toBe('10')
+  })
+
+  it('detects 30ml', () => {
+    expect(guessVolume(50, Math.round(30 * DROPS_PER_ML) - 50)).toBe('30')
+  })
+
+  it('no coconut returns no volume', () => {
+    // When cocoDrops is 0, function still returns based on total
+    // But in real code, no coconut → formVolume = ''
+    expect(guessVolume(10, 0)).toBe('single')
+  })
+
+  it('detects custom for large volumes', () => {
+    expect(guessVolume(100, 1000)).toBe('custom')
+  })
+})
+
+// ---------------------------------------------------------------------------
+// Dilution ratio calculation
+// ---------------------------------------------------------------------------
+describe('Dilution ratio', () => {
+  it('calculates ratio correctly', () => {
+    expect(Math.round(60 / 10)).toBe(6) // 1:6
+    expect(Math.round(30 / 10)).toBe(3) // 1:3
+    expect(Math.round(100 / 10)).toBe(10) // 1:10
+  })
+
+  it('snaps to nearest option', () => {
+    const options = [3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20]
+    const snap = (ratio) => options.reduce((a, b) => Math.abs(b - ratio) < Math.abs(a - ratio) ? b : a)
+    expect(snap(6)).toBe(6)
+    expect([10, 12]).toContain(snap(11)) // equidistant
+    expect(snap(13)).toBe(12)
+    expect([12, 15]).toContain(snap(14))
+    expect(snap(18)).toBe(20)
+  })
+})