anchor.diff:  
     call solvent_cells%count_particles(pos)
   
  -  call tester% assert_equal(solvent_cells%cell_start(1), 1)
  -  call tester% assert_equal(solvent_cells%cell_start(solvent_cells%N), N+1)
  -  call tester% assert_equal(sum(solvent_cells%cell_count), N)
  +  call test% assert_equal(solvent_cells%cell_start(1), 1)
  +  call test% assert_equal(solvent_cells%cell_start(solvent_cells%N), N+1)
  +  call test% assert_equal(sum(solvent_cells%cell_count), N)
   
     h = 1
     do i = 1, N
  
positive.code:   implicit none
  
    type(cell_system_t) :: solvent_cells
    type(tester_t) :: tester
  
    integer, parameter :: N = 1000000
    double precision, target, allocatable :: pos1(:, :), pos2(:, :)
  
negative.code:   allocate(pos1(3, N))
    allocate(pos2(3, N))
  
    call test% init()
  
    call random_seed(size = seed_size)
    allocate(seed(seed_size))
  