diff --git a/src/services/memory/index.js b/src/services/memory/index.js
index 986bbbf..cf7375f 100644
--- a/src/services/memory/index.js
+++ b/src/services/memory/index.js
@@ -198,10 +198,15 @@ export async function ingestEvents(events, options = {}) {
  * @returns {Promise<import('./schema.js').MemoryRecord[]>} Sorted list of relevant memories.
  */
 export async function getRelevantMemories(params) {
-  const { repository = memoryRepository, ...queryParams } = params;
+  const {
+    repository = memoryRepository,
+    ranker = filterAndRankMemories,
+    cache: cacheProvider = cache,
+    ...queryParams
+  } = params;
   const telemetry = buildTelemetryEmitter(params);
   const cacheKey = JSON.stringify(queryParams);
-  const cached = cache.get(cacheKey);
+  const cached = cacheProvider.get(cacheKey);
   if (cached) {
     telemetry('memory:retrieved', {
       agent_id: queryParams.agent_id,
@@ -220,9 +225,9 @@ export async function getRelevantMemories(params) {
     ? await repository.listMemories(queryParams)
     : [...memoryStore.values()];
 
-  const ranked = await filterAndRankMemories(source, queryParams);
+  const ranked = await ranker(source, queryParams);
   await updateMemoryUsage(repository, ranked.map((memory) => memory.id));
-  cache.set(cacheKey, ranked);
+  cacheProvider.set(cacheKey, ranked);
 
   telemetry('memory:retrieved', {
     agent_id: queryParams.agent_id,
diff --git a/test/memory-index.test.mjs b/test/memory-index.test.mjs
index 21b5ff4..1e9709f 100644
--- a/test/memory-index.test.mjs
+++ b/test/memory-index.test.mjs
@@ -1,80 +1,146 @@
 import test from 'node:test';
 import assert from 'node:assert/strict';
-import crypto from 'node:crypto';
-import { triggerPruneDryRun } from '../src/services/memory/index.js';
+import { getRelevantMemories } from '../src/services/memory/index.js';
 
-function createMemory(overrides = {}) {
+function createMockMemory(id) {
   return {
-    id: overrides.id ?? crypto.randomUUID(),
-    agent_id: overrides.agent_id ?? 'agent-1',
-    type: overrides.type ?? 'event',
-    pinned: overrides.pinned ?? false,
-    last_seen: overrides.last_seen ?? Date.now(),
-    merged_into: overrides.merged_into ?? null,
-    // Add other fields to match schema if necessary, though selectPrunableMemories mainly checks last_seen and pinned
+    id,
+    content: `content for ${id}`,
+    agent_id: 'agent-1',
+    created_at: Date.now(),
+    last_seen: Date.now(),
   };
 }
 
-test('triggerPruneDryRun uses repository listPruneCandidates if available', async () => {
-  const candidates = [createMemory({ id: 'c1' }), createMemory({ id: 'c2' })];
+test('getRelevantMemories uses cached results when available', async (t) => {
+  const cachedMemory = createMockMemory('cached-1');
+  const cacheGetMock = t.mock.fn((key) => {
+    if (key.includes('test-query')) return [cachedMemory];
+    return null;
+  });
+  const cacheSetMock = t.mock.fn();
+
+  const mockCache = {
+    get: cacheGetMock,
+    set: cacheSetMock,
+  };
+
+  const repository = {
+    listMemories: t.mock.fn(async () => []),
+    updateMemoryUsage: async () => {},
+  };
+
+  const result = await getRelevantMemories({
+    agent_id: 'agent-1',
+    query: 'test-query',
+    cache: mockCache,
+    repository,
+  });
+
+  assert.equal(result.length, 1);
+  assert.equal(result[0].id, 'cached-1');
+  assert.equal(cacheGetMock.mock.callCount(), 1);
+  // Should NOT call listMemories on cache hit
+  assert.equal(repository.listMemories.mock.callCount(), 0);
+  // Should NOT call cache.set on cache hit
+  assert.equal(cacheSetMock.mock.callCount(), 0);
+});
+
+test('getRelevantMemories calls ranker and updates cache on miss', async (t) => {
+  const memories = [createMockMemory('m1'), createMockMemory('m2')];
+  const repository = {
+    listMemories: t.mock.fn(async () => memories),
+    updateMemoryUsage: t.mock.fn(async () => {}),
+  };
+
+  // Mock ranker to reverse the list
+  const ranker = t.mock.fn(async (source) => [...source].reverse());
+
+  const cacheSetMock = t.mock.fn();
+  const mockCache = {
+    get: () => null,
+    set: cacheSetMock,
+  };
+
+  const result = await getRelevantMemories({
+    agent_id: 'agent-1',
+    query: 'test-query',
+    repository,
+    ranker,
+    cache: mockCache,
+  });
+
+  assert.equal(result.length, 2);
+  assert.equal(result[0].id, 'm2');
+  assert.equal(result[1].id, 'm1');
+
+  // Verify ranker called with correct source
+  assert.equal(ranker.mock.callCount(), 1);
+  const [sourceArg] = ranker.mock.calls[0].arguments;
+  assert.deepEqual(sourceArg, memories);
+
+  // Verify cache updated
+  assert.equal(cacheSetMock.mock.callCount(), 1);
+  const [keyArg, valueArg] = cacheSetMock.mock.calls[0].arguments;
+  assert.ok(typeof keyArg === 'string');
+  assert.deepEqual(valueArg, result); // Should cache the ranked result
+
+  // Verify memory usage updated
+  assert.equal(repository.updateMemoryUsage.mock.callCount(), 2);
+});
+
+test('getRelevantMemories passes correct parameters to ranker', async (t) => {
   const repository = {
-    listPruneCandidates: async () => candidates,
     listMemories: async () => [],
+    updateMemoryUsage: async () => {},
+  };
+  const ranker = t.mock.fn(async () => []);
+  const mockCache = { get: () => null, set: () => {} };
+
+  const params = {
+    agent_id: 'agent-1',
+    query: 'my query',
+    tags: ['a', 'b'],
+    k: 5,
+    repository,
+    ranker,
+    cache: mockCache,
   };
 
-  const result = await triggerPruneDryRun({ repository });
+  await getRelevantMemories(params);
 
-  assert.equal(result.dryRun, true);
-  assert.equal(result.candidateCount, 2);
-  assert.deepEqual(result.candidates.map(c => c.id), ['c1', 'c2']);
+  assert.equal(ranker.mock.callCount(), 1);
+  const [_, queryParams] = ranker.mock.calls[0].arguments;
+
+  assert.equal(queryParams.agent_id, 'agent-1');
+  assert.equal(queryParams.query, 'my query');
+  assert.deepEqual(queryParams.tags, ['a', 'b']);
+  assert.equal(queryParams.k, 5);
+
+  // Ensure injected deps are NOT in queryParams
+  assert.equal(queryParams.repository, undefined);
+  assert.equal(queryParams.ranker, undefined);
+  assert.equal(queryParams.cache, undefined);
 });
 
-test('triggerPruneDryRun falls back to in-memory filtering if listPruneCandidates returns empty', async () => {
-  const now = Date.now();
-  const retentionMs = 1000;
-  const oldMemory = createMemory({ id: 'old', last_seen: now - 2000 });
-  const newMemory = createMemory({ id: 'new', last_seen: now - 500 });
-
+test('getRelevantMemories triggers updateMemoryUsage on repository', async (t) => {
+  const m1 = createMockMemory('m1');
   const repository = {
-    listPruneCandidates: async () => [],
-    listMemories: async () => [oldMemory, newMemory],
+    listMemories: async () => [m1],
+    updateMemoryUsage: t.mock.fn(async () => {}),
   };
+  const ranker = async (source) => source; // identity ranker
+  const mockCache = { get: () => null, set: () => {} };
 
-  const result = await triggerPruneDryRun({ repository, retentionMs, now });
+  await getRelevantMemories({
+    agent_id: 'agent-1',
+    repository,
+    ranker,
+    cache: mockCache,
+  });
 
-  assert.equal(result.candidateCount, 1);
-  assert.equal(result.candidates[0].id, 'old');
-});
-
-test('triggerPruneDryRun handles empty candidates correctly', async () => {
-  const repository = {
-    listPruneCandidates: async () => [],
-    listMemories: async () => [],
-  };
-
-  const result = await triggerPruneDryRun({ repository });
-
-  assert.equal(result.candidateCount, 0);
-  assert.deepEqual(result.candidates, []);
-});
-
-test('triggerPruneDryRun output structure validation', async () => {
-  const memory = createMemory({ id: 'test-mem', agent_id: 'agent-x', type: 'thought', pinned: false, last_seen: 100, merged_into: 'parent-mem' });
-  const repository = {
-    listPruneCandidates: async () => [memory],
-  };
-
-  const result = await triggerPruneDryRun({ repository });
-
-  assert.equal(result.dryRun, true);
-  assert.ok(result.retentionMs > 0);
-  assert.equal(result.candidateCount, 1);
-
-  const candidate = result.candidates[0];
-  assert.equal(candidate.id, 'test-mem');
-  assert.equal(candidate.agent_id, 'agent-x');
-  assert.equal(candidate.type, 'thought');
-  assert.equal(candidate.pinned, false);
-  assert.equal(candidate.last_seen, 100);
-  assert.equal(candidate.merged_into, 'parent-mem');
+  // updateMemoryUsage helper calls repository.updateMemoryUsage for each memory
+  assert.equal(repository.updateMemoryUsage.mock.callCount(), 1);
+  const [idArg] = repository.updateMemoryUsage.mock.calls[0].arguments;
+  assert.equal(idArg, 'm1');
 });