strange error explanation comments

util/jsonutil/merge_test.go

@@ -79,6 +79,10 @@ func TestMergeClonePtr(t *testing.T) {
 		)
 
 		err := MergeClone(imp, []byte(`{"banner":nul}`))
+
+		// json-iter will produce an error since "nul" is not a valid json value. the
+		// parsing code will see the "n" and then expect "ull" to follow. the strange
+		// "expect ull" error being asserted is generated by json-iter.
 		require.EqualError(t, err, "cannot unmarshal openrtb2.Imp.Banner: expect ull")
 	})
 
@@ -142,6 +146,10 @@ func TestMergeCloneSlice(t *testing.T) {
 		)
 
 		err := MergeClone(imp, []byte(`{"iframeBuster":nul}`))
+
+		// json-iter will produce an error since "nul" is not a valid json value. the
+		// parsing code will see the "n" and then expect "ull" to follow. the strange
+		// "expect ull" error being asserted is generated by json-iter.
 		require.EqualError(t, err, "cannot unmarshal openrtb2.Imp.IframeBuster: expect ull")
 	})
 
@@ -224,6 +232,10 @@ func TestMergeCloneMap(t *testing.T) {
 		)
 
 		err := MergeClone(test, []byte(`{"foo":nul}`))
+
+		// json-iter will produce an error since "nul" is not a valid json value. the
+		// parsing code will see the "n" and then expect "ull" to follow. the strange
+		// "expect ull" error being asserted is generated by json-iter.
 		require.EqualError(t, err, "cannot unmarshal Foo: expect ull")
 	})