test(rerank): cover result-mapping edge cases in rerankResults (cppalliance#226)

Add tests for empty and absent rerank data (non-empty input still returns
empty results, degraded=false), a data item with no document (maps to empty
id/content instead of throwing), and duplicate documents (one result per
data item). Each asserts the mapped SearchResult fields. Also extract a
makePc helper to drop the repeated pc cast across the file.

Closes cppalliance#224.

Author: timon0305

src/core/pinecone/rerank.test.ts

@@ -6,6 +6,10 @@ const sampleMerged: MergedHit[] = [
   { _id: '1', _score: 0.5, chunk_text: 'hello', metadata: { k: 'v' } },
 ];
 
+function makePc(rerank: ReturnType<typeof vi.fn>) {
+  return { inference: { rerank } } as Parameters<typeof rerankResults>[0];
+}
+
 describe('rerankResults', () => {
   it('returns empty outcome when there are no merged hits', async () => {
     const pc = {} as Parameters<typeof rerankResults>[0];
@@ -23,7 +27,7 @@ describe('rerankResults', () => {
         },
       ],
     });
-    const pc = { inference: { rerank } } as Parameters<typeof rerankResults>[0];
+    const pc = makePc(rerank);
 
     const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
 
@@ -37,7 +41,7 @@ describe('rerankResults', () => {
 
   it('returns unreranked slice with degraded when rerank throws', async () => {
     const rerank = vi.fn().mockRejectedValue(new Error('rerank unavailable'));
-    const pc = { inference: { rerank } } as Parameters<typeof rerankResults>[0];
+    const pc = makePc(rerank);
 
     const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
 
@@ -47,4 +51,64 @@ describe('rerankResults', () => {
     expect(out.results[0]?.reranked).toBe(false);
     expect(out.results[0]?.content).toBe('hello');
   });
+
+  it('returns empty reranked results with degraded=false when data is an empty array', async () => {
+    const rerank = vi.fn().mockResolvedValue({ data: [] });
+    const pc = makePc(rerank);
+
+    const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
+
+    expect(out.results).toEqual([]);
+    expect(out.degraded).toBe(false);
+    expect(out.degradation_reason).toBeUndefined();
+  });
+
+  it('returns empty reranked results with degraded=false when data is absent', async () => {
+    const rerank = vi.fn().mockResolvedValue({});
+    const pc = makePc(rerank);
+
+    const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
+
+    expect(out.results).toEqual([]);
+    expect(out.degraded).toBe(false);
+  });
+
+  it('maps a rerank item with no document to an empty id/content result instead of throwing', async () => {
+    const rerank = vi.fn().mockResolvedValue({
+      data: [{ score: 0.42 }],
+    });
+    const pc = makePc(rerank);
+
+    const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
+
+    expect(out.degraded).toBe(false);
+    expect(out.results).toHaveLength(1);
+    expect(out.results[0]?.id).toBe('');
+    expect(out.results[0]?.content).toBe('');
+    expect(out.results[0]?.metadata).toEqual({});
+    expect(out.results[0]?.reranked).toBe(true);
+    expect(out.results[0]?.score).toBeCloseTo(0.42);
+  });
+
+  it('maps duplicate documents in the rerank output to one result per data item', async () => {
+    const document = { _id: '1', chunk_text: 'hello', metadata: { k: 'v' } };
+    const rerank = vi.fn().mockResolvedValue({
+      data: [
+        { score: 0.9, document },
+        { score: 0.8, document },
+      ],
+    });
+    const pc = makePc(rerank);
+
+    const out = await rerankResults(pc, 'm', 'q', sampleMerged, 5);
+
+    expect(out.degraded).toBe(false);
+    expect(out.results).toHaveLength(2);
+    expect(out.results.map((r) => r.id)).toEqual(['1', '1']);
+    expect(out.results.map((r) => r.content)).toEqual(['hello', 'hello']);
+    expect(out.results[0]?.metadata).toEqual({ k: 'v' });
+    expect(out.results[0]?.score).toBeCloseTo(0.9);
+    expect(out.results[1]?.score).toBeCloseTo(0.8);
+    expect(out.results.every((r) => r.reranked === true)).toBe(true);
+  });
 });