feat(ai): Extraction-Prompt + Gemini-Schema + Zod-Validator

tests/unit/recipe-extraction-prompt.test.ts

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+import { describe, it, expect } from 'vitest';
+import {
+  RECIPE_EXTRACTION_SYSTEM_PROMPT,
+  GEMINI_RESPONSE_SCHEMA,
+  extractionResponseSchema,
+  type ExtractionResponse
+} from '../../src/lib/server/ai/recipe-extraction-prompt';
+
+describe('recipe-extraction-prompt', () => {
+  it('system prompt is in German and mentions Rezept + Zutaten + Zubereitung', () => {
+    const p = RECIPE_EXTRACTION_SYSTEM_PROMPT.toLowerCase();
+    expect(p).toContain('rezept');
+    expect(p).toContain('zutaten');
+    expect(p).toContain('zubereitung');
+  });
+
+  it('Gemini response schema has required top-level keys', () => {
+    expect(GEMINI_RESPONSE_SCHEMA.type).toBeDefined();
+    expect(Object.keys(GEMINI_RESPONSE_SCHEMA.properties)).toEqual(
+      expect.arrayContaining(['title', 'ingredients', 'steps'])
+    );
+  });
+
+  it('Zod validator accepts a well-formed response', () => {
+    const good: ExtractionResponse = {
+      title: 'Testrezept',
+      servings_default: 4,
+      servings_unit: 'Portionen',
+      prep_time_min: 15,
+      cook_time_min: 30,
+      total_time_min: null,
+      ingredients: [{ quantity: 100, unit: 'g', name: 'Mehl', note: null }],
+      steps: [{ text: 'Mehl in eine Schüssel geben.' }]
+    };
+    expect(() => extractionResponseSchema.parse(good)).not.toThrow();
+  });
+
+  it('Zod validator rejects missing title', () => {
+    const bad = { servings_default: 4, ingredients: [], steps: [] };
+    expect(() => extractionResponseSchema.parse(bad)).toThrow();
+  });
+
+  it('Zod validator accepts quantity=null and unit=null', () => {
+    const ok: ExtractionResponse = {
+      title: 'Prise-Rezept',
+      servings_default: null,
+      servings_unit: null,
+      prep_time_min: null,
+      cook_time_min: null,
+      total_time_min: null,
+      ingredients: [{ quantity: null, unit: null, name: 'Salz', note: 'nach Geschmack' }],
+      steps: [{ text: 'Einfach so.' }]
+    };
+    expect(() => extractionResponseSchema.parse(ok)).not.toThrow();
+  });
+
+  it('Zod validator rejects unexpected extra top-level keys (strict)', () => {
+    const bad = {
+      title: 'x',
+      servings_default: null,
+      servings_unit: null,
+      prep_time_min: null,
+      cook_time_min: null,
+      total_time_min: null,
+      ingredients: [],
+      steps: [],
+      malicious_extra_field: 'pwned'
+    };
+    expect(() => extractionResponseSchema.parse(bad)).toThrow();
+  });
+});