diff --git a/tests/wqp_test.py b/tests/wqp_test.py
index fd34ae4..7170ddb 100755
--- a/tests/wqp_test.py
+++ b/tests/wqp_test.py
@@ -4,11 +4,18 @@
 
 from pandas import DataFrame
 
-from dataretrieval.wqp import (get_results, what_sites, what_organizations,
-                               what_projects, what_activities,
-                               what_detection_limits, what_habitat_metrics,
-                               what_project_weights, what_activity_metrics,
-                               _alter_kwargs)
+from dataretrieval.wqp import (
+    get_results,
+    what_sites,
+    what_organizations,
+    what_projects,
+    what_activities,
+    what_detection_limits,
+    what_habitat_metrics,
+    what_project_weights,
+    what_activity_metrics,
+    _check_mimetype,
+)
 
 
 def test_get_results(requests_mock):
@@ -171,12 +178,11 @@ def mock_request(requests_mock, request_url, file_path):
         requests_mock.get(request_url, text=text.read(), headers={"mock_header": "value"})
 
 
-class TestAlterKwargs:
-    """Tests for keyword alteration.
-    """
-    def test_alter_kwargs_mimetype(self):
-        """Tests that mimetype kwarg is altered correctly and warning is thrown."""
-        kwargs = {"mimeType": "geojson"}
-        with pytest.warns(UserWarning):
-            kwargs = _alter_kwargs(kwargs)
-        assert kwargs == {"mimeType": "csv"}
\ No newline at end of file
+def test_check_mimetype(self):
+    """Tests that correct errors are raised for invalid mimetypes."""
+    kwargs = {"mimeType": "geojson"}
+    with pytest.raises(NotImplementedError):
+        kwargs = _check_mimetype(kwargs)
+    kwargs = {"mimeType": "foo"}
+    with pytest.raises(ValueError):
+        kwargs = _check_mimetype(kwargs)