To make assertions enabled by default, first go to the Eclipse menu named Window
because Eclipse is a GUI application so it seems to be an excellent reason to put it in a menu called "Window".
Window > Preferences > Java > Installed JREs
Select the JRE that you use.
Click Edit
. Add to the Default VM Arguments
textbox the option -enableassertions
. Click Apply
if necessary.
Now, even without enabling assertions in the launch configuration, which seems to be synonymous with run configuration, programs run in Eclipse will have assertions enabled.