Add test to address issue pymc-devs#286

Author: zaxtax

pymc_experimental/tests/model/test_marginal_model.py

@@ -168,6 +168,21 @@ def test_multiple_dependent_marginalized_rvs():
     np.testing.assert_array_almost_equal(logp_x_y, ref_logp_x_y)
 
 
+def test_rv_dependent_multiple_marginalized_rvs():
+    """Test when random variables depend on multiple marginalized variables"""
+    with MarginalModel() as m:
+        x = pm.Bernoulli("x", 0.1)
+        y = pm.Bernoulli("y", 0.3)
+        z = pm.DiracDelta("z", c=x + y)
+
+    m.marginalize([x, y])
+    logp = m.compile_logp()
+
+    np.testing.assert_allclose(np.exp(logp({"z": 0})), 0.9 * 0.7)
+    np.testing.assert_allclose(np.exp(logp({"z": 1})), 0.9 * 0.3 + 0.1 * 0.7)
+    np.testing.assert_allclose(np.exp(logp({"z": 2})), 0.1 * 0.3)
+
+
 @pytest.mark.filterwarnings("error")
 def test_nested_marginalized_rvs():
     """Test that marginalization works when there are nested marginalized RVs"""