diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 5667d3d61..827ebf7a4 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -24,6 +24,6 @@ endfunction()
 #  add_fv3atm_mpi_test(${testname})
 #endforeach()
 
-foreach(testname test_post_nems_routines)
+foreach(testname test_post_nems_routines test_io)
   add_fv3atm_serial_test(${testname})
 endforeach()
diff --git a/tests/test_io.F90 b/tests/test_io.F90
new file mode 100644
index 000000000..ae9afc5de
--- /dev/null
+++ b/tests/test_io.F90
@@ -0,0 +1,55 @@
+! This program provides unit testing for the subroutines in io.
+!
+! Edward Hartnett, 8/18/24
+program test_io
+
+  use ctlblk_mod, only : komax,hyb_sigp,d3d_on,gocart_on, &
+   rdaod,nasa_on,gccpp_on,d2d_chem,modelname,submodelname, lsm
+
+  implicit none
+
+  character (len=*), parameter :: post_namelist_empty="data/post_namelist_empty.nml"
+  character (len=*), parameter :: post_namelist="data/post_namelist.nml"
+  integer :: kpo,kth,kpv
+  real(4),dimension(komax) :: po,th,pv
+  logical :: popascal
+  real, parameter :: tini=tiny(1.0)
+
+  ! Verify default settings by using empty nml file
+  call read_postnmlt(kpo,kth,kpv,po,th,pv,trim(post_namelist_empty))
+  if (kpo.ne.0) stop 1
+  if (kth.ne.6) stop 2
+  if (kpv.ne.8) stop 3
+  if (any(po.ne.0.0)) stop 4
+  if (any(abs(th(1:6)-(/310.,320.,350.,450.,550.,650./)).gt.tini)) stop 5
+  if (any(abs(pv(1:8)-(/0.5,-0.5,1.0,-1.0,1.5,-1.5,2.0,-2.0/)).gt.tini)) stop 6
+  if (.not.hyb_sigp) stop 7
+  if (d3d_on) stop 8
+  if (gocart_on) stop 9
+  if (lsm.ne.46) stop 10 ! 'lsm' is determined by 'popascal'
+  if (rdaod) stop 11
+  if (nasa_on) stop 12
+  if (gccpp_on) stop 13
+  if (d2d_chem) stop 14
+
+  ! Now use fully populated nml file
+  call read_postnmlt(kpo,kth,kpv,po,th,pv,trim(post_namelist))
+  if (kpo.ne.5) stop 101
+  if (kth.ne.7) stop 102
+  if (kpv.ne.9) stop 103
+  if (po(1).ne.0.5) stop 104
+  if (any(po(2:komax).ne.1.0)) stop 104
+  if (any(abs(th(1:7)-(/1.,2.,3.,4.,5.,6.,7./)).gt.tini)) stop 105
+  if (any(abs(pv(1:9)-(/11.,12.,13.,14.,15.,16.,17.,18.,19./)).gt.tini)) stop 106
+  if (hyb_sigp) stop 107
+  if (.not.d3d_on) stop 108
+  if (.not.gocart_on) stop 109
+  if (lsm.ne.5) stop 110 ! 'lsm' is determined by 'popascal'
+  if (.not.rdaod) stop 111
+  if (.not.nasa_on) stop 112
+  if (.not.gccpp_on) stop 113
+  if (.not.d2d_chem) stop 114
+  if (trim(modelname).ne."DMMY") stop 115
+  if (trim(submodelname).ne."SUBM") stop 116
+
+end program test_io