(%i1) display2d:false$
(%i2) expr:exp(-abs(x));
(%o2) %e^-abs(x)
(%i3) integrate(expr,x,minf,0);
(%o3) 1 <<< correct
(%i4) assume(x<0);
(%o4) [x < 0]
(%i5) integrate(expr,x,minf,0);
defint: integral is divergent. <<< assumption shouldn't change result!
-- an error. To debug this try: debugmode(true);
Maxima 5.25.1 http://maxima.sourceforge.net
using Lisp GNU Common Lisp (GCL) GCL 2.6.8 (a.k.a. GCL)