//Testing the case where Line In Surface goes until the boundary of the domain
lc=0.1; //mesh size parameter
//Points
Point(1) = {0, 0, 0, lc};
Point(2) = {1, 0, 0, lc};
Point(3) = {1, 1, 0, lc};
Point(4) = {0, 1, 0, lc};
Point(5) = {0.5, 0.2, 0, lc};
Point(6) = {0.5, 1, 0, lc};
//Lines
Line(1) = {1, 2};
Line(2) = {2, 3};
Line(3) = {3, 4};
Line(4) = {4, 1};
Line(5) = {5, 6};
//Loop
Line Loop(10) = {1,2,3,4};
Plane Surface(1) = {10};
Line{5} In Surface{1}; 
//Mesh
Mesh 2;