test: add test for StatsmodelsDE with NegativeBinomial model

tests/test_de.py

@@ -1,6 +1,7 @@
 import anndata as ad
 import numpy as np
 import pytest
+import statsmodels.api as sm
 from pydeseq2.utils import load_example_data
 
 import multi_condition_comparisions
@@ -28,11 +29,22 @@ def test_adata():
     return ad.AnnData(X=counts, obs=metadata)
 
 
-@pytest.mark.parametrize("method_class", [StatsmodelsDE])
-def test_de(test_adata, method_class: BaseMethod):
+@pytest.mark.parametrize(
+    "method_class,kwargs",
+    [
+        # OLS
+        (StatsmodelsDE, {}),
+        # Negative Binomial
+        (
+            StatsmodelsDE,
+            {"regression_model": sm.GLM, "family": sm.families.NegativeBinomial()},
+        ),
+    ],
+)
+def test_de(test_adata, method_class: BaseMethod, kwargs):
     """Check that the method can be initialized and fitted and that the test_contrast
     method returns a dataframe with the correct number of rows"""
     method = method_class(adata=test_adata, design="~condition")
-    method.fit()
+    method.fit(**kwargs)
     res_df = method.test_contrasts(np.array([0, 1]))
     assert len(res_df) == test_adata.n_vars