diff --git a/lib/spark.js b/lib/spark.js
index add0e33..06ae27f 100644
--- a/lib/spark.js
+++ b/lib/spark.js
@@ -3,7 +3,7 @@
 import { ActivityState } from './activity-state.js'
 import { SPARK_VERSION, MAX_CAR_SIZE, APPROX_ROUND_LENGTH_IN_MS } from './constants.js'
 import { queryTheIndex } from './ipni-client.js'
-import { getMinerPeerId } from './miner-info.js'
+import { getMinerPeerId as defaultGetMinerPeerId } from './miner-info.js'
 import {
   encodeHex
 } from '../vendor/deno-deps.js'
@@ -12,12 +12,16 @@ const sleep = dt => new Promise(resolve => setTimeout(resolve, dt))
 
 export default class Spark {
   #fetch
+  #getMinerPeerId
   #activity = new ActivityState()
   #maxTasksPerNode = 360
 
-  constructor ({ fetch = globalThis.fetch } = {}) {
+  constructor ({
+    fetch = globalThis.fetch,
+    getMinerPeerId = defaultGetMinerPeerId
+  } = {}) {
     this.#fetch = fetch
-    this.getMinerPeerId = getMinerPeerId
+    this.#getMinerPeerId = getMinerPeerId
   }
 
   async getRetrieval () {
@@ -43,7 +47,7 @@ export default class Spark {
   async executeRetrievalCheck (retrieval, stats) {
     console.log(`Calling Filecoin JSON-RPC to get PeerId of miner ${retrieval.minerId}`)
     try {
-      const peerId = await this.getMinerPeerId(retrieval.minerId)
+      const peerId = await this.#getMinerPeerId(retrieval.minerId)
       console.log(`Found peer id: ${peerId}`)
       stats.providerId = peerId
     } catch (err) {
diff --git a/test/integration.js b/test/integration.js
index b282207..4873a57 100644
--- a/test/integration.js
+++ b/test/integration.js
@@ -18,12 +18,13 @@ test('integration', async () => {
 })
 
 test('retrieval check for our CID', async () => {
-  const spark = new Spark()
-  spark.getRetrieval = async () => ({ cid: KNOWN_CID, minerId: OUR_FAKE_MINER_ID })
-  spark.getMinerPeerId = async (minerId) => {
+  const getMinerPeerId = async (minerId) => {
     assertEquals(minerId, OUR_FAKE_MINER_ID)
     return FRISBEE_PEER_ID
   }
+  const spark = new Spark({ getMinerPeerId })
+  spark.getRetrieval = async () => ({ cid: KNOWN_CID, minerId: OUR_FAKE_MINER_ID })
+
   const measurementId = await spark.nextRetrieval()
   const res = await fetch(`https://api.filspark.com/measurements/${measurementId}`)
   assert(res.ok)