diff --git a/api/material.yaml b/api/material.yaml
index a3b80da..5e8bc13 100644
--- a/api/material.yaml
+++ b/api/material.yaml
@@ -79,6 +79,8 @@
     responses:
       200:
         $ref: 'api.yaml#/components/responses/Ok'
+      400:
+        $ref: 'api.yaml#/components/responses/400'
       401:
         $ref: 'api.yaml#/components/responses/401'
       403:
diff --git a/api/sample.yaml b/api/sample.yaml
index 8ba92af..e911d9c 100644
--- a/api/sample.yaml
+++ b/api/sample.yaml
@@ -123,7 +123,7 @@
 
 /sample/notes/fields:
   get:
-    summary: TODO list all existing field names for custom notes fields
+    summary: list all existing field names for custom notes fields
     description: 'Auth: all, levels: read, write, maintain, dev, admin'
     tags:
       - /sample
diff --git a/package.json b/package.json
index d3f9e63..9a69ea2 100644
--- a/package.json
+++ b/package.json
@@ -7,7 +7,8 @@
     "tsc": "tsc",
     "test": "mocha dist/**/**.spec.js",
     "start": "tsc && node dist/index.js || exit 1",
-    "dev": "nodemon -e ts,yaml --exec \"npm run start\""
+    "dev": "nodemon -e ts,yaml --exec \"npm run start\"",
+    "loadDev": "node dist/test/loadDev.js"
   },
   "keywords": [],
   "author": "",
diff --git a/src/routes/material.spec.ts b/src/routes/material.spec.ts
index aa9a484..dbc646b 100644
--- a/src/routes/material.spec.ts
+++ b/src/routes/material.spec.ts
@@ -1,6 +1,6 @@
 import should from 'should/as-function';
 import MaterialModel from '../models/material';
-import TestHelper from "../helpers/test";
+import TestHelper from "../test/helper";
 
 
 describe('/material', () => {
@@ -271,20 +271,28 @@ describe('/material', () => {
     it('deletes the material', done => {
       TestHelper.request(server, done, {
         method: 'delete',
-        url: '/material/100000000000000000000001',
+        url: '/material/100000000000000000000002',
         auth: {basic: 'janedoe'},
         httpStatus: 200
       }).end((err, res) => {
         if (err) return done(err);
         should(res.body).be.eql({status: 'OK'});
-        MaterialModel.findById('100000000000000000000001').lean().exec((err, data) => {
+        MaterialModel.findById('100000000000000000000002').lean().exec((err, data) => {
           if (err) return done(err);
           should(data).be.null();
           done();
         });
       });
     });
-    it('rejects deleting a material referenced by samples');
+    it('rejects deleting a material referenced by samples', done => {
+      TestHelper.request(server, done, {
+        method: 'delete',
+        url: '/material/100000000000000000000004',
+        auth: {basic: 'janedoe'},
+        httpStatus: 400,
+        res: {status: 'Material still in use'}
+      })
+    });
     it('rejects an invalid id', done => {
       TestHelper.request(server, done, {
         method: 'delete',
diff --git a/src/routes/material.ts b/src/routes/material.ts
index 29362e2..292f02f 100644
--- a/src/routes/material.ts
+++ b/src/routes/material.ts
@@ -2,8 +2,10 @@ import express from 'express';
 
 import MaterialValidate from './validate/material';
 import MaterialModel from '../models/material'
+import SampleModel from '../models/sample';
 import IdValidate from './validate/id';
 import res400 from './validate/res400';
+import mongoose from 'mongoose';
 
 
 const router = express.Router();
@@ -69,14 +71,21 @@ router.put('/material/' + IdValidate.parameter(), (req, res, next) => {
 router.delete('/material/' + IdValidate.parameter(), (req, res, next) => {
   if (!req.auth(res, ['write', 'maintain', 'dev', 'admin'], 'basic')) return;
 
-  MaterialModel.findByIdAndDelete(req.params.id).lean().exec((err, data) => {
+  // check if there are still samples referencing this material
+  SampleModel.find({'material_id': new mongoose.Types.ObjectId(req.params.id)}).lean().exec((err, data) => {
     if (err) return next(err);
-    if (data) {
-      res.json({status: 'OK'})
-    }
-    else {
-      res.status(404).json({status: 'Not found'});
+    if (data.length) {
+      return res.status(400).json({status: 'Material still in use'});
     }
+    MaterialModel.findByIdAndDelete(req.params.id).lean().exec((err, data) => {
+      if (err) return next(err);
+      if (data) {
+        res.json({status: 'OK'})
+      }
+      else {
+        res.status(404).json({status: 'Not found'});
+      }
+    });
   });
 });
 
diff --git a/src/routes/root.spec.ts b/src/routes/root.spec.ts
index 25be1ba..f8a803f 100644
--- a/src/routes/root.spec.ts
+++ b/src/routes/root.spec.ts
@@ -1,4 +1,4 @@
-import TestHelper from "../helpers/test";
+import TestHelper from "../test/helper";
 
 
 describe('/', () => {
diff --git a/src/routes/sample.spec.ts b/src/routes/sample.spec.ts
index 98017f0..aa01a39 100644
--- a/src/routes/sample.spec.ts
+++ b/src/routes/sample.spec.ts
@@ -2,7 +2,7 @@ import should from 'should/as-function';
 import SampleModel from '../models/sample';
 import NoteModel from '../models/note';
 import NoteFieldModel from '../models/note_field';
-import TestHelper from "../helpers/test";
+import TestHelper from "../test/helper";
 
 
 describe('/sample', () => {
diff --git a/src/routes/sample.ts b/src/routes/sample.ts
index 7415912..fe12ed0 100644
--- a/src/routes/sample.ts
+++ b/src/routes/sample.ts
@@ -10,7 +10,6 @@ import NoteFieldModel from '../models/note_field';
 import IdValidate from './validate/id';
 
 
-
 const router = express.Router();
 
 router.get('/samples', (req, res, next) => {
@@ -129,6 +128,7 @@ router.post('/sample/new', async (req, res, next) => {
     delete sample.notes;
     sample.note_id = data._id;
     sample.user_id = req.authDetails.id;
+    console.log(sample);
     new SampleModel(sample).save((err, data) => {
       if (err) return next(err);
       res.json(SampleValidate.output(data.toObject()));
diff --git a/src/routes/template.spec.ts b/src/routes/template.spec.ts
index 6a4c7af..fa9361f 100644
--- a/src/routes/template.spec.ts
+++ b/src/routes/template.spec.ts
@@ -1,7 +1,7 @@
 import should from 'should/as-function';
 import TemplateTreatmentModel from '../models/treatment_template';
 import TemplateMeasurementModel from '../models/measurement_template';
-import TestHelper from "../helpers/test";
+import TestHelper from "../test/helper";
 
 
 describe('/template', () => {
diff --git a/src/routes/user.spec.ts b/src/routes/user.spec.ts
index a3a0ed9..e294cb2 100644
--- a/src/routes/user.spec.ts
+++ b/src/routes/user.spec.ts
@@ -1,6 +1,6 @@
 import should from 'should/as-function';
 import UserModel from '../models/user';
-import TestHelper from "../helpers/test";
+import TestHelper from "../test/helper";
 
 
 describe('/user', () => {
diff --git a/src/helpers/test.ts b/src/test/helper.ts
similarity index 98%
rename from src/helpers/test.ts
rename to src/test/helper.ts
index 6c2fa72..26cb5a5 100644
--- a/src/helpers/test.ts
+++ b/src/test/helper.ts
@@ -28,7 +28,7 @@ export default class TestHelper {
     server = require('../index');
     db.drop(err => {  // reset database
       if (err) return done(err);
-      db.loadJson(require('../test/db.json'), done);
+      db.loadJson(require('./db.json'), done);
     });
     return server
   }
diff --git a/src/test/loadDev.ts b/src/test/loadDev.ts
new file mode 100644
index 0000000..690044d
--- /dev/null
+++ b/src/test/loadDev.ts
@@ -0,0 +1,12 @@
+import db from '../db';
+
+db.connect('dev', () => {
+  console.info('dropping data...');
+  db.drop(() => {  // reset database
+    console.info('loading data...');
+    db.loadJson(require('./db.json'), () => {
+      console.info('done');
+      process.exit(0);
+    });
+  });
+});