diff --git a/ddlpy/ddlpy.py b/ddlpy/ddlpy.py
index e884dcc..ddd5552 100644
--- a/ddlpy/ddlpy.py
+++ b/ddlpy/ddlpy.py
@@ -272,7 +272,6 @@ def _combine_waarnemingenlijst(result, location):
         "Naam",
         "X",
         "Y",
-        "Parameter_Wat_Omschrijving",
     ]:
         df[name] = location[name]
 
diff --git a/tests/test_ddlpy.py b/tests/test_ddlpy.py
index 86061e6..370b459 100755
--- a/tests/test_ddlpy.py
+++ b/tests/test_ddlpy.py
@@ -10,14 +10,14 @@
 import numpy as np
 
 
-@pytest.fixture
+@pytest.fixture(scope="session")
 def locations():
     """return all locations"""
     locations = ddlpy.locations()
     return locations
 
 
-@pytest.fixture
+@pytest.fixture(scope="session")
 def location(locations):
     """return sample location"""
     bool_grootheid = locations['Grootheid.Code'] == 'WATHTE'
@@ -26,7 +26,7 @@ def location(locations):
     return location
 
 
-@pytest.fixture
+@pytest.fixture(scope="session")
 def measurements(location):
     """measurements for a location """
     start_date = dt.datetime(1953, 1, 1)
@@ -40,6 +40,13 @@ def test_locations(locations):
     assert locations.shape[1] == 18
     # the number of rows is the number of stations, so will change over time
     assert locations.shape[0] > 1
+    
+    # check presence of columns
+    assert "Coordinatenstelsel" in locations.columns
+    assert "Naam" in locations.columns
+    assert "X" in locations.columns
+    assert "Y" in locations.columns
+    assert "Parameter_Wat_Omschrijving" in locations.columns
 
 
 def test_locations_extended():
@@ -55,6 +62,14 @@ def test_locations_extended():
 
 def test_measurements(measurements):
     assert measurements.shape[0] > 1
+    
+    # check presence of columns
+    assert "Coordinatenstelsel" in measurements.columns
+    assert "Naam" in measurements.columns
+    assert "X" in measurements.columns
+    assert "Y" in measurements.columns
+    assert "Parameter_Wat_Omschrijving" in measurements.columns
+    assert "Code" in measurements.columns
 
 
 def test_measurements_freq_yearly(location, measurements):
@@ -67,8 +82,8 @@ def test_measurements_freq_yearly(location, measurements):
 def test_measurements_freq_none(location, measurements):
     start_date = dt.datetime(1953, 1, 1)
     end_date = dt.datetime(1953, 4, 1)
-    measurements_yearly = ddlpy.measurements(location, start_date=start_date, end_date=end_date, freq=None)
-    assert measurements.shape == measurements_yearly.shape
+    measurements_monthly = ddlpy.measurements(location, start_date=start_date, end_date=end_date, freq=None)
+    assert measurements.shape == measurements_monthly.shape
 
 
 def test_measurements_available(location):
diff --git a/tests/test_endpoints.py b/tests/test_endpoints.py
index d46389a..84a04de 100755
--- a/tests/test_endpoints.py
+++ b/tests/test_endpoints.py
@@ -4,18 +4,17 @@
 """Tests for `ddlpy` package."""
 
 import pytest
-
 import requests
-
-from ddlpy import ddlpy
+import ddlpy
 
 
-@pytest.fixture
+@pytest.fixture(scope="session")
 def endpoints():
     """
     Get the endpoints from the api
     """
-    return ddlpy.ENDPOINTS
+    return ddlpy.ddlpy.ENDPOINTS
+
 
 @pytest.fixture
 def collect_catalogue_resp(endpoints):
@@ -56,6 +55,7 @@ def check_observations_available_resp(endpoints):
 def test_check_observations_available(check_observations_available_resp):
     assert check_observations_available_resp.status_code == 200
 
+
 @pytest.fixture
 def collect_number_of_observations_resp(endpoints):
     endpoint = endpoints['collect_number_of_observations']
@@ -65,6 +65,7 @@ def collect_number_of_observations_resp(endpoints):
 def test_collect_number_of_observations(collect_number_of_observations_resp):
     assert collect_number_of_observations_resp.status_code == 200
 
+
 @pytest.fixture
 def request_bulk_observations_resp(endpoints):
     endpoint = endpoints['request_bulk_observations']
diff --git a/tests/test_utils.py b/tests/test_utils.py
index f06796a..d7dbf2b 100755
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -3,17 +3,17 @@
 
 """Tests for `utils` package."""
 
-from ddlpy import utils
+from ddlpy.utils import date_series
 import datetime
 
 
-def test_content():
+def test_date_series():
     """Sample pytest test function with the pytest fixture as an argument."""
     # from bs4 import BeautifulSoup
     # assert 'GitHub' in BeautifulSoup(response.content).title.string
     start = datetime.datetime(2018, 1, 1)
     end = datetime.datetime(2018, 3, 1)
-    result = utils.date_series(start, end)
+    result = date_series(start, end)
     expected = [
         (datetime.datetime(2018, 1, 1, 0, 0), datetime.datetime(2018, 2, 1, 0, 0)),
         (datetime.datetime(2018, 2, 1, 0, 0), datetime.datetime(2018, 3, 1, 0, 0))
@@ -22,7 +22,7 @@ def test_content():
 
     start = datetime.datetime(2017, 11, 15)
     end = datetime.datetime(2018, 3, 5)
-    result = utils.date_series(start, end)
+    result = date_series(start, end)
     expected = [
         (datetime.datetime(2017, 11, 15, 0, 0), datetime.datetime(2017, 12, 15, 0, 0)),
         (datetime.datetime(2017, 12, 15, 0, 0), datetime.datetime(2018, 1, 15, 0, 0)),