diff --git a/simpunch/tests/test_starfield.py b/simpunch/tests/test_starfield.py
index 9ef307b..0a89c4f 100644
--- a/simpunch/tests/test_starfield.py
+++ b/simpunch/tests/test_starfield.py
@@ -34,21 +34,26 @@ def _sample_ndcube(shape: tuple, code: str = "PM1", level: str = "0") -> NDCube:
 
 
 @pytest.fixture
-def sample_ndcollection(shape: tuple) -> NDCollection:
-    wcs = WCS(naxis=2)
-    wcs.wcs.ctype = "HPLN-ARC", "HPLT-ARC"
-    wcs.wcs.cunit = "deg", "deg"
-    wcs.wcs.cdelt = 0.1, 0.1
-    wcs.wcs.crpix = 0, 0
-    wcs.wcs.crval = 1, 1
-    wcs.wcs.cname = "HPC lon", "HPC lat"
-
-    input_data = NDCube(np.random.random(shape).astype(np.float32), wcs=wcs)
-    return NDCollection(
-        [("-60.0 deg", input_data),
-         ("0.0 deg", input_data),
-         ("60.0 deg", input_data)],
-        aligned_axes="all")
+def sample_ndcollection():
+    def _create_sample_ndcollection(shape: tuple) -> NDCollection:
+        wcs = WCS(naxis=2)
+        wcs.wcs.ctype = ["HPLN-ARC", "HPLT-ARC"]
+        wcs.wcs.cunit = ["deg", "deg"]
+        wcs.wcs.cdelt = [0.1, 0.1]
+        wcs.wcs.crpix = [shape[1] // 2, shape[0] // 2]  # Center pixel for the WCS
+        wcs.wcs.crval = [1, 1]
+        wcs.wcs.cname = ["HPC lon", "HPC lat"]
+
+        input_data = NDCube(np.random.random(shape).astype(np.float32), wcs=wcs)
+
+        return NDCollection(
+            [("-60.0 deg", input_data),
+             ("0.0 deg", input_data),
+             ("60.0 deg", input_data)],
+            aligned_axes="all"
+        )
+    return _create_sample_ndcollection
+
 
 
 def test_starfield(sample_ndcube: NDCube) -> None:
@@ -62,8 +67,10 @@ def test_starfield(sample_ndcube: NDCube) -> None:
 
 def test_polarized_starfield(sample_ndcollection: NDCollection) -> None:
     """Test polarized starfield generation."""
-    input_data = sample_ndcollection((2048, 2048))
+    shape = (2048, 2048)
+    input_data = sample_ndcollection(shape)
 
     output_data = add_starfield_polarized(input_data)
 
     assert isinstance(output_data, NDCollection)
+    assert len(output_data) == 3