test: expand memory hybrid coverage

src/memory/hybrid.test.ts

@@ -0,0 +1,87 @@
+import { describe, expect, it } from "vitest";
+
+import { bm25RankToScore, buildFtsQuery, mergeHybridResults } from "./hybrid.js";
+
+describe("memory hybrid helpers", () => {
+  it("buildFtsQuery tokenizes and AND-joins", () => {
+    expect(buildFtsQuery("hello world")).toBe("\"hello\" AND \"world\"");
+    expect(buildFtsQuery("FOO_bar baz-1")).toBe("\"FOO_bar\" AND \"baz\" AND \"1\"");
+    expect(buildFtsQuery("   ")).toBeNull();
+  });
+
+  it("bm25RankToScore is monotonic and clamped", () => {
+    expect(bm25RankToScore(0)).toBeCloseTo(1);
+    expect(bm25RankToScore(1)).toBeCloseTo(0.5);
+    expect(bm25RankToScore(10)).toBeLessThan(bm25RankToScore(1));
+    expect(bm25RankToScore(-100)).toBeCloseTo(1);
+  });
+
+  it("mergeHybridResults unions by id and combines weighted scores", () => {
+    const merged = mergeHybridResults({
+      vectorWeight: 0.7,
+      textWeight: 0.3,
+      vector: [
+        {
+          id: "a",
+          path: "memory/a.md",
+          startLine: 1,
+          endLine: 2,
+          source: "memory",
+          snippet: "vec-a",
+          vectorScore: 0.9,
+        },
+      ],
+      keyword: [
+        {
+          id: "b",
+          path: "memory/b.md",
+          startLine: 3,
+          endLine: 4,
+          source: "memory",
+          snippet: "kw-b",
+          textScore: 1.0,
+        },
+      ],
+    });
+
+    expect(merged).toHaveLength(2);
+    const a = merged.find((r) => r.path === "memory/a.md");
+    const b = merged.find((r) => r.path === "memory/b.md");
+    expect(a?.score).toBeCloseTo(0.7 * 0.9);
+    expect(b?.score).toBeCloseTo(0.3 * 1.0);
+  });
+
+  it("mergeHybridResults prefers keyword snippet when ids overlap", () => {
+    const merged = mergeHybridResults({
+      vectorWeight: 0.5,
+      textWeight: 0.5,
+      vector: [
+        {
+          id: "a",
+          path: "memory/a.md",
+          startLine: 1,
+          endLine: 2,
+          source: "memory",
+          snippet: "vec-a",
+          vectorScore: 0.2,
+        },
+      ],
+      keyword: [
+        {
+          id: "a",
+          path: "memory/a.md",
+          startLine: 1,
+          endLine: 2,
+          source: "memory",
+          snippet: "kw-a",
+          textScore: 1.0,
+        },
+      ],
+    });
+
+    expect(merged).toHaveLength(1);
+    expect(merged[0]?.snippet).toBe("kw-a");
+    expect(merged[0]?.score).toBeCloseTo(0.5 * 0.2 + 0.5 * 1.0);
+  });
+});
+