Initialization of a variable in Fortran at declaration vs. at runtime

test_fortran_init.f90

program test_fortran_init
  implicit none
  
  print *, "test with init at declaration"
  call test_routine
  call test_routine

  print *, "test with init at subroutine start"
  call test_routine_2
  call test_routine_2
end program

subroutine test_routine
  implicit none
  integer :: var = 0

  print *, "var = ", var
  var = var + 1
  print *, "var = ", var
end subroutine

subroutine test_routine_2
  implicit none
  integer :: var

  var = 0
  print *, "var = ", var
  var = var + 1
  print *, "var = ", var
end subroutine

! expected screen output:
!  test with init at declaration
! var =            0
! var =            1
! var =            1
! var =            2
! test with init at subroutine start
! var =            0
! var =            1
! var =            0
! var =            1