diff --git a/.github/workflows/io_gnu_yml.old b/.github/workflows/io_gnu_yml.old
new file mode 100644
index 000000000..def5a1402
--- /dev/null
+++ b/.github/workflows/io_gnu_yml.old
@@ -0,0 +1,122 @@
+name: io_gnu
+on: [push, pull_request, workflow_dispatch]
+
+# Cancel in-progress workflows when pushing to a branch
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+env:
+  cache_key: gnu11-1
+  CC: gcc-10
+  FC: gfortran-10
+  CXX: g++-10
+
+
+# Split into a steup step, and a WW3 build step which
+# builds multiple switches in a matrix. The setup is run once and
+# the environment is cached so each build of WW3 can share the dependencies.
+
+jobs:
+  setup:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: checkout-ww3
+        if: steps.cache-env.outputs.cache-hit != 'true'
+        uses: actions/checkout@v3
+        with:
+            path: ww3
+      # Cache spack, OASIS, and compiler
+      # No way to flush Action cache, so key may have # appended
+      - name: cache-env
+        id: cache-env
+        uses: actions/cache@v3
+        with:
+          path: |
+            spack
+            ~/.spack
+            work_oasis3-mct
+          key: spack-${{ runner.os }}-${{ env.cache_key }}-${{ hashFiles('ww3/model/ci/spack_gnu.yaml') }}
+
+      # Build WW3 spack environment
+      - name: install-dependencies-with-spack
+        if: steps.cache-env.outputs.cache-hit != 'true'
+        run: |
+          # Install NetCDF, ESMF, g2, etc using Spack
+          sudo apt install cmake
+          git clone -c feature.manyFiles=true https://github.com/JCSDA/spack.git
+          source spack/share/spack/setup-env.sh
+          spack env create ww3-gnu ww3/model/ci/spack_gnu.yaml
+          spack env activate ww3-gnu
+          spack compiler find
+          spack external find cmake
+          spack add mpich@3.4.2
+          spack concretize
+          spack install --dirty -v
+
+      - name: build-oasis
+        if: steps.cache-env.outputs.cache-hit != 'true'
+        run: |
+          source spack/share/spack/setup-env.sh
+          spack env activate ww3-gnu
+          export WWATCH3_DIR=${GITHUB_WORKSPACE}/ww3/model
+          export OASIS_INPUT_PATH=${GITHUB_WORKSPACE}/ww3/regtests/ww3_tp2.14/input/oasis3-mct
+          export OASIS_WORK_PATH=${GITHUB_WORKSPACE}/ww3/regtests/ww3_tp2.14/input/work_oasis3-mct
+          cd ww3/regtests/ww3_tp2.14/input/oasis3-mct/util/make_dir
+          cmake .
+          make VERBOSE=1
+          cp -r ${GITHUB_WORKSPACE}/ww3/regtests/ww3_tp2.14/input/work_oasis3-mct ${GITHUB_WORKSPACE}
+
+  io_gnu:
+    needs: setup
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: install-dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install doxygen gcovr valgrind
+
+      - name: checkout-ww3
+        uses: actions/checkout@v3
+        with:
+            path: ww3
+
+      - name: cache-env
+        id: cache-env
+        uses: actions/cache@v3
+        with:
+          path: |
+            spack
+            ~/.spack
+            work_oasis3-mct
+          key: spack-${{ runner.os }}-${{ env.cache_key }}-${{ hashFiles('ww3/model/ci/spack_gnu.yaml') }}
+
+      - name: build-ww3
+        run: |
+          source spack/share/spack/setup-env.sh
+          spack env activate ww3-gnu
+          set -x
+          cd ww3
+          export CC=mpicc
+          export FC=mpif90
+          export OASISDIR=${GITHUB_WORKSPACE}/work_oasis3-mct
+          mkdir build && cd build
+          export LD_LIBRARY_PATH="/home/runner/work/WW3/WW3/spack/var/spack/environments/ww3-gnu/.spack-env/view/:$LD_LIBRARY_PATH"
+          cmake -DSWITCH=${GITHUB_WORKSPACE}/ww3/regtests/unittests/data/switch.io -DCMAKE_BUILD_TYPE=Debug -DCMAKE_Fortran_FLAGS="-g -fprofile-abs-path -fprofile-arcs -ftest-coverage -O0 -Wall -fno-omit-frame-pointer -fsanitize=address" -DCMAKE_C_FLAGS="-g -fprofile-abs-path -fprofile-arcs -ftest-coverage -O0 -Wall -fno-omit-frame-pointer -fsanitize=address" ..
+          make -j2 VERBOSE=1
+          ./bin/ww3_grid
+          mv mod_def.ww3 regtests/unittests
+          ctest --verbose --output-on-failure --rerun-failed
+          gcovr --root .. -v  --html-details --exclude ../regtests/unittests --exclude CMakeFiles --print-summary -o test-coverage.html &> /dev/null
+        
+      - name: upload-test-coverage
+        uses: actions/upload-artifact@v3
+        with:
+          name: ww3-test-coverage
+          path: |
+            ww3/build/*.html
+            ww3/build/*.css
+
+          
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 58115b3aa..5436f9cb1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -58,3 +58,9 @@ if(NOT CMAKE_BUILD_TYPE MATCHES "^(Debug|Release|RelWithDebInfo|MinSizeRel)$")
 endif()
 
 add_subdirectory(model)
+
+# Turn on unit testing.
+include(CTest)
+if(BUILD_TESTING)
+  add_subdirectory(regtests/unittests)
+endif()
diff --git a/regtests/unittests/CMakeLists.txt b/regtests/unittests/CMakeLists.txt
new file mode 100644
index 000000000..69445bfb7
--- /dev/null
+++ b/regtests/unittests/CMakeLists.txt
@@ -0,0 +1,39 @@
+# This is the CMake file for the model/tests directory in the WW3
+# project. 
+#
+# Ed Hartnett, 10/14/23
+
+# Some very small test files may be committed to the repo. This
+# function copies such a data file to the build directory.
+function(copy_test_data name)
+  message(STATUS "Copying ${name} to ${CMAKE_CURRENT_BINARY_DIR}")
+  file(COPY "${CMAKE_CURRENT_SOURCE_DIR}/data/${name}"
+    DESTINATION ${CMAKE_CURRENT_BINARY_DIR}
+    FILE_PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ)
+endfunction()
+
+# Some very small test files may be committed to the repo. This
+# function copies such a data file to the build directory.
+function(copy_test_data_2 srcname destname)
+  message(STATUS "Copying ${srcname} to ${CMAKE_CURRENT_BINARY_DIR}/${destname}")
+  file(COPY "${CMAKE_CURRENT_SOURCE_DIR}/data/${srcname}"
+    DESTINATION "${CMAKE_BINARY_DIR}"
+    FILE_PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ)
+  file(RENAME "${CMAKE_BINARY_DIR}/${srcname}" "${CMAKE_BINARY_DIR}/${destname}")
+endfunction()
+
+# Function to build and run a test.
+function(unit_test name)
+  add_executable(${name} ${name}.F90)
+  target_link_libraries(${name} PRIVATE ww3_lib)
+  add_test(NAME ${name} COMMAND ${name})
+endfunction()
+
+# Copy test data files that are in the repo to the build directory.
+copy_test_data(switch.io)
+copy_test_data_2(ww3_grid.inp ww3_grid.inp)
+
+# Build and run the tests.
+unit_test(test_io_points_bin)
+
+
diff --git a/regtests/unittests/data/switch.io b/regtests/unittests/data/switch.io
new file mode 100644
index 000000000..c97e44765
--- /dev/null
+++ b/regtests/unittests/data/switch.io
@@ -0,0 +1 @@
+NOGRB SHRD PR1 FLX2 LN0 ST0 NL0 BT0 DB0 TR0 BS0 IC0 IS0 REF0 WNT1 WNX1 CRT1 CRX1 O0 O1 O2 O3 O4 O5 O6 O7 O10 O11
\ No newline at end of file
diff --git a/regtests/unittests/data/ww3_grid.inp b/regtests/unittests/data/ww3_grid.inp
new file mode 100644
index 000000000..6f45604f3
--- /dev/null
+++ b/regtests/unittests/data/ww3_grid.inp
@@ -0,0 +1,48 @@
+$ WAVEWATCH III Grid preprocessor input file
+$ ------------------------------------------
+  '1-D REFRACTION X              '
+$
+   1.25 0.08  3  24  0.
+$
+   F T F T F F
+  300. 300. 150. 300.
+$
+  &PRO1 CFLTM = 0.75 /
+  &PRO2 CFLTM = 0.75 /
+  &PRO3 CFLTM = 0.75, WDTHCG = 0., WDTHTH = 0. /
+  &PRO4 CFLTM = 0.75, RNFAC = 0., RSFAC = 0. /
+END OF NAMELISTS
+$
+  'RECT' F 'NONE'
+   13  3
+    5.E3   5.E3  1.
+   -5.E3  -5.E3  1.
+$
+  -1. 1. 10  -1. 2 1 '(....)' 'UNIT' 'input'
+$
+$ First grid
+$
+  50 50 50 45 40 35 30 25 20 15 10  5  0
+  50 50 50 45 40 35 30 25 20 15 10  5  0
+  50 50 50 45 40 35 30 25 20 15 10  5  0
+$
+$ Second grid
+$
+$  0  5 10 15 20 25 30 35 40 45 50 50 50
+$  0  5 10 15 20 25 30 35 40 45 50 50 50
+$  0  5 10 15 20 25 30 35 40 45 50 50 50
+$
+  10  1 1 '(....)' 'PART' 'input'
+$
+$ First grid
+$
+   2  2  F
+$
+$ Second grid
+$
+$ 12  2  F
+   0  0  F
+   0  0  F
+   0  0
+$
+   0. 0. 0. 0.  0
diff --git a/regtests/unittests/data/ww3_outp.inp b/regtests/unittests/data/ww3_outp.inp
new file mode 100644
index 000000000..dd728819f
--- /dev/null
+++ b/regtests/unittests/data/ww3_outp.inp
@@ -0,0 +1,8 @@
+$
+ 20100101 000000 3600 1
+$
+ 1
+ -1
+$
+ 4
+ 2 30 20100101 000000 'UTC'
diff --git a/regtests/unittests/test_io_points_bin.F90 b/regtests/unittests/test_io_points_bin.F90
new file mode 100644
index 000000000..69c197bce
--- /dev/null
+++ b/regtests/unittests/test_io_points_bin.F90
@@ -0,0 +1,152 @@
+! This is a test for model IO for WW3. This tests the legacy (binary)
+! output of points data, done by function W3IOPO().
+!
+! Ed Hartnett 10/14/23
+program test_io_points_bin
+  use w3iopomd
+  use w3gdatmd
+  use w3wdatmd
+  use w3odatmd
+  use w3iogrmd
+  use w3adatmd  
+  implicit none
+  
+  integer, target :: i
+  integer :: ndsop, iotest, ndsbul, ndsm
+  integer :: ndstrc, ntrace
+  character*7 expected_ptnme
+  character*6 my_fmt
+  real :: expected_loc_1
+  integer :: write_test_file
+
+  print *, 'Testing WW3 binary point file code.'
+
+  ! These are mysterious but have to be called or else the IPASS
+  ! variable does not exist and w3iopo() crashes.
+  call w3nmod(1, 6, 6)
+  call w3setg(1, 6, 6)
+  call w3ndat(6, 6)
+  call w3setw(1, 6, 6)
+  call w3nout(6, 6)
+  call w3seto(1, 6, 6)
+
+  ndsm   = 20
+  ndsop  = 20
+  ndsbul = 0
+  ndstrc =  6
+  ntrace = 10
+  
+  ! Create a point output file needed for this test.
+  if (write_test_file() .ne. 0) stop 1
+
+  write (ndso,900)
+900 FORMAT (/15X,'    *** WAVEWATCH III Point output post.***    '/ &
+       15X,'==============================================='/)
+
+  ! 2.  Read model definition file.
+  CALL W3IOGR('READ', NDSM)
+  WRITE (NDSO,920) GNAME
+920 FORMAT ('  Grid name : ',A/)  
+
+  ! This will not work. But cannot be tested because it will change the value of IPASS,
+!  call w3iopo('EAD', ndsop, iotest)
+!  if (iotest .ne. 1) stop 7
+
+  ! Read the file out_pnt.ww3 from the model/tests/data directory.
+  call w3iopo('READ', ndsop, iotest)
+  if (iotest .ne. 0) stop 10
+  close(ndsop)
+
+  ! Make sure we got the values we expected.
+  if (nopts .ne. 11) stop 11
+  expected_loc_1 = 0.0
+  do i = 1, nopts
+     ! Check ptnme and ptloc arrays.
+     print *, ptnme(i), ptloc(1, i), ptloc(2, i)
+     if (i .lt. 10) then
+        my_fmt = '(a,i1)'
+     else
+        my_fmt = '(a,i2)'
+     endif
+     write(fmt = my_fmt, unit=expected_ptnme) 'Point', i
+     if (ptnme(i) .ne. expected_ptnme) stop 20
+     print *, expected_loc_1
+     if (ptloc(1, i) .ne. expected_loc_1) stop 21
+     expected_loc_1 = expected_loc_1 + 5000.0
+     if (ptloc(2, i) .ne. 0) stop 22
+  end do
+  
+  print *, 'OK!'
+  print *, 'SUCCESS!'
+end program test_io_points_bin
+
+integer function write_test_file()
+  implicit none
+
+  integer :: ntlu, nk, nth, nopts
+  character(len=10), parameter :: veropt = '2021-04-06'
+  character(len=31), parameter :: idstr = 'WAVEWATCH III POINT OUTPUT FILE'
+  real :: ptloc(2,11) = reshape((/ 0., 0., 5000., 0., 10000., 0., 15000., 0., &
+       20000., 0., 25000., 0., 30000., 0., 35000., 0., 40000., 0., 45000., 0., 50000., 0. /), &
+       (/ 2, 11 /))
+  character*40 ptnme(11)
+  integer :: time(2) = (/ 19680606, 0 /)
+  integer :: nspec = 72
+  integer :: iw(11) = (/ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 /)
+  integer :: ii(11) = (/ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 /)
+  integer :: il(11) = (/ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 /)
+  real :: iceo(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)
+  real :: iceho(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)    
+  real :: icefo(11) = (/ 1000., 1000., 1000., 1000., 1000., 1000., 1000., 1000., 1000., 1000., 1000. /)    
+  real :: dpo(11) = (/ 50., 50., 45., 40., 35., 30., 25., 20., 15., 10., 5. /)
+  real :: wao(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)      
+  real :: wdo(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)
+  real :: aso(11) = (/ -999.900024, -999.900024, -999.900024, -999.900024, -999.900024, &
+       -999.900024, -999.900024, -999.900024, -999.900024, -999.900024, -999.900024 /)    
+  real :: cao(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)
+  real :: cdo(11) = (/ 0., 0., 0., 0., 0., 0., 0., 0., 0., 0., 0. /)
+  character*13 :: grdid(11)
+  real :: spco(72, 11)
+  integer :: i, j
+  integer :: ierr
+
+  ! Initialize some values.
+  ntlu = 21
+  nk = 3
+  nth = 24
+  nopts = 11
+  do i = 1, nopts
+     if (i .le. 9) then
+        write(ptnme(i), '(a,i1)') 'Point', i
+     else
+        write(ptnme(i), '(a,i2)') 'Point', i
+     endif
+     grdid(i) = 'ww3          '
+  end do
+
+  ! Open the file.
+  open(ntlu, file="out_pnt.ww3", form="unformatted", status="replace", &
+       action="write", convert="big_endian", iostat=ierr)
+  if (ierr .ne. 0) stop 111
+
+  ! Write our values.
+  write (ntlu, iostat=ierr) idstr, veropt, nk, nth, nopts
+  if (ierr .ne. 0) stop 112
+  write (ntlu, iostat=ierr) ((ptloc(j,i),j=1,2),i=1,nopts), (ptnme(i),i=1,nopts)
+  if (ierr .ne. 0) stop 113
+  write (ntlu, iostat=ierr) time
+  if (ierr .ne. 0) stop 114
+  do i=1, nopts
+     write (ntlu, iostat=ierr) iw(i), ii(i), il(i), dpo(i), wao(i), wdo(i),      &
+          aso(i), cao(i), cdo(i), iceo(i), iceho(i),        &
+          icefo(i), grdid(i), (spco(j,i),j=1,nspec)
+     if (ierr .ne. 0) stop 115
+  enddo
+
+  ! Close the file.
+  close(ntlu)
+
+  ! We're done!
+  write_test_file = 0
+end function write_test_file
+