fypp depndency and memtest for autodiff

pyproject.toml

@@ -1,2 +1,2 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "scikit-build", "cmake>=3.12", "ninja", "numpy", "cython"]
+requires = ["setuptools>=42", "wheel", "scikit-build", "cmake>=3.12", "ninja", "numpy", "cython","fypp"]

tests/memtest.f90

@@ -20,6 +20,7 @@ program memtest
   call test_custom_binary_diffusion(pcs)
   call test_update_vertical_grid(pcs)
   call test_press_temp_edd(pcs)
+  call test_autodiff(pcs)
 
 contains
 
@@ -308,5 +309,34 @@ subroutine test_press_temp_edd(pc)
     endif
 
   end subroutine
+
+  subroutine test_autodiff(pc)
+    type(Atmosphere), intent(inout) :: pc
+
+    character(:), allocatable :: err
+    real(dp) :: tn
+
+    pc%var%autodiff = .true.
+    pc%var%atol = 1.0e-20_dp
+
+    call pc%initialize_stepper(pc%var%usol_init, err)
+    if (allocated(err)) then
+      print*,trim(err)
+      stop 1
+    endif
+
+    tn = pc%step(err)
+    if (allocated(err)) then
+      print*,trim(err)
+      stop 1
+    endif
+
+    call pc%destroy_stepper(err)
+    if (allocated(err)) then
+      print*,trim(err)
+      stop 1
+    endif
+
+  end subroutine
 
 end program