diff --git a/tests/test_util.py b/tests/test_util.py
index 600c014..88ea5d1 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -29,7 +29,6 @@
 
 from datetime import datetime, date, time
 from decimal import Decimal
-from numpy import float64, int64
 
 import pytest
 
@@ -88,12 +87,6 @@ def test_json_serial():
     d = Decimal(1.0)
     assert util.json_serial(d) == 1.0
 
-    d = int64(500_000_000_000)
-    assert util.json_serial(d) == 500_000_000_000
-
-    d = float64(500.00000005)
-    assert util.json_serial(d) == 500.00000005
-
     with pytest.raises(TypeError):
         util.json_serial('foo')
 
diff --git a/tests/test_xarray_zarr_provider.py b/tests/test_xarray_zarr_provider.py
index 539f3d2..6e59906 100644
--- a/tests/test_xarray_zarr_provider.py
+++ b/tests/test_xarray_zarr_provider.py
@@ -27,9 +27,12 @@
 #
 # =================================================================
 
+from numpy import float64, int64
+
 import pytest
 
 from pygeoapi.provider.xarray_ import XarrayProvider
+from pygeoapi.util import json_serial
 
 from .util import get_test_file_path
 
@@ -86,3 +89,11 @@ def test_query(config):
 
     data = p.query(format_='zarr')
     assert isinstance(data, bytes)
+
+
+def test_numpy_json_serial():
+    d = int64(500_000_000_000)
+    assert json_serial(d) == 500_000_000_000
+
+    d = float64(500.00000005)
+    assert json_serial(d) == 500.00000005