diff --git a/tests/test_all.py b/tests/test_all.py
index 13274fd..56da312 100644
--- a/tests/test_all.py
+++ b/tests/test_all.py
@@ -1,6 +1,9 @@
+import numpy as np
+import pysindy as ps
 import pytest
 
 from gen_experiments.typing import NestedDict
+from gen_experiments.utils import unionize_coeff_matrices
 
 
 def test_flatten_nested_dict():
@@ -19,3 +22,16 @@ def test_flatten_nested_bad_dict():
     with pytest.raises(TypeError, match="Only string keys allowed"):
         deep = NestedDict(a={1: 1})
         deep.flatten()
+
+
+def test_unionize_coeff_matrices():
+    # lib = ps.PolynomialLibrary().fit(np.array([[1, 1]]))
+    model = ps.SINDy(feature_names=["x", "y"])
+    data = np.arange(10)
+    data = np.vstack((data, data)).T
+    model.fit(data, 0.1)
+    coeff_true = [{"y": -1, "zorp_x": 0.1}, {"x": 1, "zorp_y": 0.1}]
+    true, est, feats = unionize_coeff_matrices(model, coeff_true)
+    assert len(feats) == true.shape[1]
+    assert len(feats) == est.shape[1]
+    assert est.shape == true.shape