diff --git a/include/autoppl/expression/traits.hpp b/include/autoppl/expression/traits.hpp
index bb4c83d2..9d39d3d9 100644
--- a/include/autoppl/expression/traits.hpp
+++ b/include/autoppl/expression/traits.hpp
@@ -16,6 +16,7 @@ struct var_traits
     using pointer_t = typename VarType::pointer_t;
     using state_t = typename VarType::state_t;
 
+    // TODO may have to move this to a different class for compile-time checking
     static_assert(std::is_convertible_v<VarType, value_t>);
 };
 
diff --git a/test/distribution/normal_unittest.cpp b/test/distribution/normal_unittest.cpp
index 939bac7d..9b229a8c 100644
--- a/test/distribution/normal_unittest.cpp
+++ b/test/distribution/normal_unittest.cpp
@@ -32,6 +32,15 @@ TEST_F(normal_dist_fixture, simple_gaussian) {
     EXPECT_DOUBLE_EQ(dist1.log_pdf(0.0), std::log(dist1.pdf(0.0)));
     EXPECT_DOUBLE_EQ(dist1.log_pdf(-0.5), std::log(dist1.pdf(-0.5)));
     EXPECT_DOUBLE_EQ(dist1.log_pdf(4), std::log(dist1.pdf(4)));
+
+
+    EXPECT_DOUBLE_EQ(dist2.pdf(0.0), 0.3989422804014327);
+    EXPECT_DOUBLE_EQ(dist2.pdf(-0.5), 0.3520653267642995);
+    EXPECT_DOUBLE_EQ(dist2.pdf(4), 0.00013383022576488537);
+
+    EXPECT_DOUBLE_EQ(dist2.log_pdf(0.0), std::log(dist2.pdf(0.0)));
+    EXPECT_DOUBLE_EQ(dist2.log_pdf(-0.5), std::log(dist2.pdf(-0.5)));
+    EXPECT_DOUBLE_EQ(dist2.log_pdf(4), std::log(dist1.pdf(4)));
 }
 
 } // ppl
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