I made one Atlas Map based on this exercise (https://anitagraser.com/2016/10/15/qgis-atlas-tutorial-material-design/) and I had good results working with QGIS 2.18.
But when I use QGIS 3.4 I can not get the same results.
As you can see in this picture bellow in QGIS 2.18 I have this notification when I run the filter test:
This is what happens when I run the same filter code in QGIS 3.4:
Filter expression parsing error:
$atlasfeatureid function is not known
$map function is not known
So in this case - What do I need to do?