diff --git a/CHANGES.md b/CHANGES.md
index 76a4785..316cd58 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -3,7 +3,8 @@
 ## 0.74 (unreleased)
 
 
-- Nothing changed yet.
+- Improved GLD-Bulk
+- Added testing to GLD-Bulk
 
 
 ## 0.73 (2024-12-19)
diff --git a/api/bro_upload/gld_bulk_upload.py b/api/bro_upload/gld_bulk_upload.py
index b24286d..76efaaf 100644
--- a/api/bro_upload/gld_bulk_upload.py
+++ b/api/bro_upload/gld_bulk_upload.py
@@ -161,8 +161,8 @@ def process(self) -> None:
 
         # BRO-Ids
         bro_ids = all_measurements_df.to_series(0).unique()
-        progress = 80 / len(
-            bro_ids * 2
+        progress = 80 / (
+            len(bro_ids) * 2
         )  # amount of progress per steps, per bro_id two steps.
         for bro_id in bro_ids:
             # Step 2: Prepare data for uploadtask per row
@@ -236,7 +236,7 @@ def file_to_df(file_instance: T) -> pl.DataFrame:
             df = pl.concat(dfs)
     else:
         raise ValueError(
-            "Unsupported file type. Only CSV and Excel files are supported."
+            "Unsupported file type. Only CSV and Excel, or ZIP files are supported."
         )
     return df
 
diff --git a/api/tests/test_bulk_upload.py b/api/tests/test_gar_bulk_upload.py
similarity index 100%
rename from api/tests/test_bulk_upload.py
rename to api/tests/test_gar_bulk_upload.py
diff --git a/api/tests/test_gld_bulk_upload.py b/api/tests/test_gld_bulk_upload.py
new file mode 100644
index 0000000..f3cc3e5
--- /dev/null
+++ b/api/tests/test_gld_bulk_upload.py
@@ -0,0 +1,93 @@
+import json
+from unittest.mock import patch
+
+import pandas as pd
+import pytest
+from rest_framework.test import APIClient
+
+from api.tests import fixtures
+
+user = fixtures.user
+organisation = fixtures.organisation  # imported, even though not used in this file, because required for userprofile fixture
+userprofile = fixtures.userprofile
+
+
+@pytest.fixture
+def api_client():
+    return APIClient()
+
+
+@pytest.mark.django_db
+def test_gld_bulk_upload_invalid_input(
+    api_client, organisation, user, userprofile, tmp_path
+):
+    """Testing the 400 response on a request with just 1 file."""
+    api_client.force_authenticate(user=user)
+    url = "/api/bulkuploads/"
+
+    data = {"bulk_upload_type": "GLD"}
+
+    d = tmp_path / "sub"
+    d.mkdir()
+    file_path = d / "test.csv"
+    csv_data = {"test1": ["test1", "test2"], "test2": ["test1", "test3"]}
+    df = pd.DataFrame(csv_data)
+    df.to_csv(file_path, index=False)
+
+    with file_path.open("rb") as fp:
+        data["measurements_tvp_file"] = fp
+        r = api_client.post(url, data, format="multipart")
+
+    assert r.status_code == 400
+
+
+@pytest.mark.django_db
+def test_gld_bulk_upload_valid_input(
+    api_client, organisation, user, userprofile, tmp_path
+):
+    """Testing the 201 response on a valid request."""
+    api_client.force_authenticate(user=user)
+    url = "/api/bulkuploads/"
+
+    d = tmp_path / "sub"
+    d.mkdir()
+    file_path = d / "test.csv"
+    csv_data = {"test1": ["test1", "test2"], "test2": ["test1", "test3"]}
+    df = pd.DataFrame(csv_data)
+    df.to_csv(file_path, index=False)
+
+    metadata_json = json.dumps(
+        {
+            "broId": "GLD000000076375",
+            "projectNumber": "1889",
+            "qualityRegime": "IMBRO",
+            "requestReference": "test_request",
+            "deliveryAccountableParty": "17278718",
+        }
+    )
+
+    sourcedocument_json = json.dumps(
+        {
+            "investigatorKvk": "17278718",
+            "observationType": "reguliereMeting",
+            "processReference": "NEN5120v1991",
+            "evaluationProcedure": "brabantWater2013",
+            "statusQualityControl": "volledigBeoordeeld",
+            "measurementInstrumentType": "druksensor",
+            "airPressureCompensationType": "KNMImeting",
+        }
+    )
+
+    with file_path.open("rb") as fp:
+        data = {
+            "bulk_upload_type": "GLD",
+            "project_number": 1,
+            "metadata": metadata_json,
+            "sourcedocument_data": sourcedocument_json,
+            "measurement_tvp_file": fp,
+        }
+        with patch("api.tasks.gld_bulk_upload_task.delay") as mock_task:
+            r = api_client.post(url, data, format="multipart")
+
+    assert mock_task.called
+    assert r.status_code == 201
diff --git a/api/tests/test_gld_bulk_uploader.py b/api/tests/test_gld_bulk_uploader.py
new file mode 100644
index 0000000..6f4aefb
--- /dev/null
+++ b/api/tests/test_gld_bulk_uploader.py
@@ -0,0 +1,38 @@
+import uuid
+
+import pytest
+from django.core.exceptions import ValidationError
+from rest_framework.test import APIClient
+
+from api import models as api_models
+from api.bro_upload.gld_bulk_upload import GLDBulkUploader
+from api.tests import fixtures
+
+user = fixtures.user
+organisation = fixtures.organisation  # imported, even though not used in this file, because required for userprofile fixture
+userprofile = fixtures.userprofile
+
+
+@pytest.fixture
+def api_client():
+    return APIClient()
+
+
+@pytest.mark.django_db
+def test_gld_bulk_uploader_invalid_init():
+    """Testing the init of the GLDBulkUploader."""
+    with pytest.raises(ValidationError):
+        GLDBulkUploader(
+            bulk_upload_instance_uuid="test",
+            measurement_tvp_file_uuid="test2",
+            bro_password="pass",
+            bro_username="user",
+        )
+
+    with pytest.raises(api_models.BulkUpload.DoesNotExist):
+        GLDBulkUploader(
+            bulk_upload_instance_uuid=uuid.uuid4(),
+            measurement_tvp_file_uuid=uuid.uuid4(),
+            bro_password="pass",
+            bro_username="user",
+        )