diff --git a/server/tests/unit/nest/ski-routing/ski-router-runner.test.ts b/server/tests/unit/nest/ski-routing/ski-router-runner.test.ts
index a2d8f1333..197556c80 100644
--- a/server/tests/unit/nest/ski-routing/ski-router-runner.test.ts
+++ b/server/tests/unit/nest/ski-routing/ski-router-runner.test.ts
@@ -21,6 +21,7 @@ import {
   WorkerSkiRouterRunner,
 } from '../../../../src/nest/ski-routing/worker-router-runner';
 import { decodePolyline } from '../../../../src/utils/polyline';
+import { oneByOne } from '../../../helpers/one-by-one';
 import { SkiWorld } from '../../../helpers/ski-world';
 import { skiRouteRequestSchema } from '@trek/shared';
 
@@ -222,7 +223,9 @@ describe('WorkerSkiRouterRunner', () => {
       );
       await expect(runner.run(job(['hang']))).rejects.toThrow('busy');
       // One job at a time is with the thread, each on its own clock.
-      for (let i = 0; i < MAX_WAITING_JOBS; i++) await vi.advanceTimersByTimeAsync(answerTimeoutMs(job(['hang'])));
+      await oneByOne(Array.from({ length: MAX_WAITING_JOBS }), () =>
+        vi.advanceTimersByTimeAsync(answerTimeoutMs(job(['hang']))),
+      );
       expect(await Promise.all(waiting)).toEqual(Array.from({ length: MAX_WAITING_JOBS }, () => 'timeout'));
       await runner.close();
     } finally {
diff --git a/server/tests/unit/nest/tours.mcp.test.ts b/server/tests/unit/nest/tours.mcp.test.ts
index 1f71bac83..18daeef7d 100644
--- a/server/tests/unit/nest/tours.mcp.test.ts
+++ b/server/tests/unit/nest/tours.mcp.test.ts
@@ -30,6 +30,7 @@ import { makeDayAssignment } from '../../helpers/factories/itinerary';
 import { makePlace } from '../../helpers/factories/places';
 import { countRows, findRow, insertRows, updateRows } from '../../helpers/factories/rows';
 import { addTourWaypoints, makeTour, markStationVisit } from '../../helpers/factories/tours';
+import { oneByOne } from '../../helpers/one-by-one';
 import { resetTestDb } from '../../helpers/test-db';
 import { createTestModule, type TestModule } from '../../helpers/test-module';
 import { createTestOrm } from '../../helpers/test-orm';
@@ -766,12 +767,12 @@ describe('ToursMcp', () => {
       ski_discipline: 'alpine',
       ski_options: JSON.stringify({ options, build: '2026-11-02' }),
     });
-    for (const place of [timed, untimed]) {
-      await addTourWaypoints(orm, place.id, [
+    await oneByOne([timed, untimed], (place) =>
+      addTourWaypoints(orm, place.id, [
         { lat: 46, lng: 7, station_key: `${place.id}-a` },
         { lat: 46.01, lng: 7, station_key: `${place.id}-b` },
-      ]);
-    }
+      ]),
+    );
     await orm.close();
     const plan = read(await mcp.getTourPlan({ tripId: trip.id, placeId: partly.id }, ctx(member.id)));
     expect(plan.legs.map((leg: { kind: string }) => leg.kind)).toEqual(['free', 'routed']);
diff --git a/server/tests/unit/nest/trek-places.client.test.ts b/server/tests/unit/nest/trek-places.client.test.ts
index d1d6cc815..61ba695f9 100644
--- a/server/tests/unit/nest/trek-places.client.test.ts
+++ b/server/tests/unit/nest/trek-places.client.test.ts
@@ -23,6 +23,7 @@ import {
   serviceLang,
   type TrekPlace,
 } from '../../../src/nest/maps/trek-places.client';
+import { oneByOne } from '../../helpers/one-by-one';
 
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
 
@@ -1089,9 +1090,9 @@ describe('the layers breaker', () => {
 
   it('TREK-PLACES-BREAKER-01: busy layer answers never stop place search', async () => {
     stubFetch({ detail: 'busy' }, 503);
-    for (let i = 0; i < 4; i++) {
-      await expect(trekPlacesRoutes(VIEW, 'horse', CAPS)).rejects.toThrow(/503/);
-    }
+    await oneByOne(Array.from({ length: 4 }), () =>
+      expect(trekPlacesRoutes(VIEW, 'horse', CAPS)).rejects.toThrow(/503/),
+    );
     stubFetch({ query: 'x', results: [PLACE] });
     await expect(trekPlacesSearch('x')).resolves.toHaveLength(1);
     expect(calls).toHaveLength(1);
@@ -1099,7 +1100,7 @@ describe('the layers breaker', () => {
 
   it('TREK-PLACES-BREAKER-02: the layers stop dialling on their own after a few failures', async () => {
     stubFetch({ detail: 'busy' }, 503);
-    for (let i = 0; i < 4; i++) await expect(trekPlacesWays([1])).rejects.toThrow(/503/);
+    await oneByOne(Array.from({ length: 4 }), () => expect(trekPlacesWays([1])).rejects.toThrow(/503/));
     const dialled = calls.length;
     await expect(trekPlacesRoutes(VIEW, 'horse', CAPS)).rejects.toThrow('unreachable, not retrying yet');
     await expect(trekPlacesWays([1])).rejects.toThrow('unreachable, not retrying yet');
@@ -1108,7 +1109,7 @@ describe('the layers breaker', () => {
 
   it('TREK-PLACES-BREAKER-03: a layer not built yet does not clear the count of search failures', async () => {
     stubFetch({}, 503);
-    for (let i = 0; i < 3; i++) await expect(trekPlacesSearch('x')).rejects.toThrow(/503/);
+    await oneByOne(Array.from({ length: 3 }), () => expect(trekPlacesSearch('x')).rejects.toThrow(/503/));
     stubFetch({ detail: 'not built' }, 404);
     await expect(trekPlacesWays([1])).rejects.toThrow(/404/);
     stubFetch({}, 503);