diff --git a/test/idGenerator.test.js b/test/idGenerator.test.js
index 21f0821..afdf2a2 100644
--- a/test/idGenerator.test.js
+++ b/test/idGenerator.test.js
@@ -11,12 +11,13 @@ if (Buffer.isEncoding('base64url')) {
     t.plan(cacheSize)
     const ids = new Set()
 
-    for (let i = 0; i < (cacheSize); ++i) {
+    for (let i = 0; i < cacheSize; ++i) {
       const id = idGen()
       if (ids.has(id)) {
         t.assert.ifError('had a collision')
       }
       t.assert.strictEqual(id.length, 32)
+      ids.add(id)
     }
   })
 }
@@ -26,11 +27,12 @@ test('should have no collisions, base64', async (t) => {
   t.plan(cacheSize)
   const ids = new Set()
 
-  for (let i = 0; i < (cacheSize); ++i) {
+  for (let i = 0; i < cacheSize; ++i) {
     const id = idGen()
     if (ids.has(id)) {
       t.assert.ifError('had a collision')
     }
     t.assert.strictEqual(id.length, 32)
+    ids.add(id)
   }
 })