Test: separate expression build and showing it

mapytex/calculus/API/expression.py

@@ -136,9 +136,11 @@ class Expression(object):
         :returns: TODO
 
         :example:
-        >>> Expression.random("{a}/{a*k}") # doctest: +SKIP
+        >>> e = Expression.random("{a}/{a*k}")
+        >>> e # doctest: +SKIP
         <Exp: -3 / -15>
-        >>> Expression.random("{a}/{a*k} - 3*{b}", variables_scope={'a':{'min_max':(10, 30)}}) # doctest: +SKIP
+        >>> e = Expression.random("{a}/{a*k} - 3*{b}", variables_scope={'a':{'min_max':(10, 30)}})
+        >>> e # doctest: +SKIP
         <Exp: 18 / 108 - 3 * 9>
         >>> e = Expression.random("{a}*x + {b}*x + 3", ["a>b"], rejected=[0, 1])
         >>> ee = e.simplify()