Initial commit: Sibilla — self-hosted Perplexity-like AI search engine

- Flask web app with Perplexity-style search + synthesis pipeline
- Degoog → SearXNG → DuckDuckGo cascading search backends
- Gemini LLM for query expansion + answer synthesis with citations
- MCP server exposing search tools via stdio
- 57 unit tests covering all modules

tests/test_prompts.py

@@ -0,0 +1,79 @@
+"""Tests for sibilla.prompts — prompt templates and builders."""
+
+from sibilla.prompts import (
+    SYNTHESIS_SYSTEM_PROMPT,
+    FALLBACK_PROMPT,
+    QUERY_REWRITE_PROMPT,
+    build_synthesis_prompt,
+)
+
+
+class TestPromptTemplates:
+    """Verify all prompt templates are non-empty and well-formed."""
+
+    def test_synthesis_system_prompt_not_empty(self):
+        assert len(SYNTHESIS_SYSTEM_PROMPT) > 50
+        assert "Sibilla" in SYNTHESIS_SYSTEM_PROMPT
+        assert "[1]" in SYNTHESIS_SYSTEM_PROMPT
+
+    def test_fallback_prompt_not_empty(self):
+        assert len(FALLBACK_PROMPT) > 20
+        assert "Sibilla" in FALLBACK_PROMPT
+
+    def test_query_rewrite_prompt_has_placeholder(self):
+        assert "{num_variants}" in QUERY_REWRITE_PROMPT
+
+
+class TestBuildSynthesisPrompt:
+    """Test build_synthesis_prompt with various inputs."""
+
+    def test_minimal_prompt(self):
+        sources = [
+            {"index": 1, "title": "Test", "url": "https://example.com", "content": "Hello world"}
+        ]
+        prompt = build_synthesis_prompt("what is this?", sources)
+
+        assert "what is this?" in prompt
+        assert "Test" in prompt
+        assert "https://example.com" in prompt
+        assert "Hello world" in prompt
+        assert "[1]" in prompt
+
+    def test_multiple_sources(self):
+        sources = [
+            {"index": 1, "title": "A", "url": "https://a.com", "content": "Content A"},
+            {"index": 2, "title": "B", "url": "https://b.com", "content": "Content B"},
+            {"index": 3, "title": "C", "url": "https://c.com", "content": "Content C"},
+        ]
+        prompt = build_synthesis_prompt("query", sources)
+
+        assert "--- Fonte [1] ---" in prompt
+        assert "--- Fonte [2] ---" in prompt
+        assert "--- Fonte [3] ---" in prompt
+        assert "Content A" in prompt
+        assert "Content B" in prompt
+        assert "Content C" in prompt
+
+    def test_with_date_context(self):
+        sources = [{"index": 1, "title": "X", "url": "https://x.com", "content": "Y"}]
+        prompt = build_synthesis_prompt("q", sources, date_context="Data: 16 Luglio 2026")
+
+        assert "16 Luglio 2026" in prompt
+        assert "Contesto temporale" in prompt
+
+    def test_empty_sources(self):
+        prompt = build_synthesis_prompt("query", [])
+        assert "query" in prompt
+        assert "### Fonti da utilizzare" in prompt
+
+    def test_source_missing_fields(self):
+        sources = [{"index": 1}]  # missing title, url, content
+        prompt = build_synthesis_prompt("q", sources)
+        assert "Senza titolo" in prompt  # fallback title
+        assert "[1]" in prompt
+
+    def test_source_with_snippet_fallback(self):
+        """When 'content' is missing, fall back to 'snippet'."""
+        sources = [{"index": 1, "title": "T", "url": "https://t.com", "snippet": "snippet text"}]
+        prompt = build_synthesis_prompt("q", sources)
+        assert "snippet text" in prompt