diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
index e4d67029f..b6220c6e3 100644
--- a/.github/pull_request_template.md
+++ b/.github/pull_request_template.md
@@ -35,3 +35,8 @@ Do PRs in upstream repositories need to be merged first?
 If so add the "waiting for other repos" label and list the upstream PRs
 - waiting on noaa-emc/nems/pull/<pr_number>
 - waiting on noaa-emc/fv3atm/pull/<pr_number>
+
+# Requirements before merging
+- [ ] All new code in this PR is tested by at least one unit test
+- [ ] All new code in this PR includes Doxygen documentation
+- [ ] All new code in this PR does not add new compilation warnings (check CI output)
diff --git a/.github/workflows/GCC.yml b/.github/workflows/GCC.yml
index 5f3891684..86d0bf668 100644
--- a/.github/workflows/GCC.yml
+++ b/.github/workflows/GCC.yml
@@ -24,7 +24,7 @@ jobs:
         mpi: ["mpich", "openmpi"]
 
     steps:
-
+        
     - name: checkout-fv3atm
       uses: actions/checkout@v4
       with:
@@ -59,6 +59,7 @@ jobs:
         spack config add "packages:mpi:require:'${{ matrix.mpi }}'"
         spack concretize |& tee ${SPACK_ENV}/log.concretize
         spack install -j2 --fail-fast
+        echo "spackrc=$?" >> ${GITHUB_ENV}
         spack clean --all
 
   build_fv3atm:
@@ -73,9 +74,20 @@ jobs:
 
     steps:
 
-    - name: install-doxygen
+    # Only do Doxygen and gcovr build for one job
+    - name: decide-doc-gcovr-build
+      run: |
+        if [[ "${{ matrix.cmake_opts }}" == "-D32BIT=ON" && "${{ matrix.gcc_ver }}" == 12 && "${{ matrix.mpi }}" == mpich ]]; then
+          echo 'devbuild=ON' | tee -a ${GITHUB_ENV}
+          echo 'gcov_cmake="-DCMAKE_Fortran_FLAGS=-fprofile-abs-path -fprofile-arcs -ftest-coverage -O0"' | tee -a ${GITHUB_ENV}
+        else
+          echo 'devbuild=OFF' | tee -a ${GITHUB_ENV}
+        fi
+
+    - name: install-utilities
       run: |
         sudo apt-get install doxygen graphviz
+        python3 -m pip install gcovr
 
     - name: install-cmake
       run: |
@@ -109,14 +121,34 @@ jobs:
         export CC=mpicc
         export CXX=mpicxx
         export FC=mpif90
-        cat /home/runner/work/fv3atm/fv3atm/spack-develop/opt/spack/linux-ubuntu22.04-zen2/gcc-12.3.0/fms-2023.04-*/lib/cmake/fms/fms-config.cmake
-        cmake ${GITHUB_WORKSPACE}/fv3atm -DBUILD_TESTING=ON ${{ matrix.cmake_opts }} -DENABLE_DOCS=ON
+        cmake ${GITHUB_WORKSPACE}/fv3atm -DBUILD_TESTING=ON ${{ matrix.cmake_opts }} -DENABLE_DOCS=ON ${{ env.gcov_cmake }}
         make -j2
-        ls -l /home/runner/work/fv3atm/fv3atm/fv3atm/io
 
-    - uses: actions/upload-artifact@v4
+    - name: run-tests
+      run: |
+        cd $GITHUB_WORKSPACE/build
+        ctest -j2 --output-on-failure --rerun-failed
+
+    - name: get-test-coverage
+      if: ${{ env.devbuild == 'ON' }}
+      run: |
+        cd $GITHUB_WORKSPACE/build
+        gcovr -r .. -v --html-details --gcov-executable gcov-12 --exclude $GITHUB_WORKSPACE/fv3atm/tests --exclude $GITHUB_WORKSPACE/fv3atm/stochastic_physics_repo --exclude $GITHUB_WORKSPACE/fv3atm/build/ccpp --exclude $GITHUB_WORKSPACE/fv3atm/ccpp/physics --exclude $GITHUB_WORKSPACE/fv3atm/ccpp/framework --exclude $GITHUB_WORKSPACE/fv3atm/atmos_cubed_sphere  --exclude CMakeFiles --print-summary -o test-coverage.html
+
+    - name: upload-test-coverage
+      uses: actions/upload-artifact@v4
+      if: ${{ env.devbuild == 'ON' }}
+      with:
+        name: test-coverage-fv3atm-${{ github.sha }}
+        path: |
+              ${{ github.workspace }}/build/*.html 
+              ${{ github.workspace }}/build/*.css
+
+    - name: upload-docs
+      uses: actions/upload-artifact@v4
+      if: ${{ env.devbuild == 'ON' }}
       with:
-        name: docs-gcc${{ matrix.gcc_ver }}-${{ matrix.mpi }}-${{ matrix.cmake_opts }}
+        name: docs-fv3atm
         path: |
           build/docs/html
 
@@ -126,4 +158,3 @@ jobs:
       with:
         name: ccpp_prebuild_logs-gcc${{ matrix.gcc_ver }}-${{ matrix.mpi }}-${{ matrix.cmake_opts }}
         path: ${{ github.workspace }}/build/ccpp/ccpp_prebuild.*
-
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c310110ca..ae94fef14 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -157,6 +157,11 @@ if(OPENMP)
   target_link_libraries(fv3atm PUBLIC OpenMP::OpenMP_Fortran)
 endif()
 
+if(BUILD_TESTING)
+  include(CTest)
+  add_subdirectory(tests)
+endif()
+
 ###############################################################################
 ### Install
 ###############################################################################
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
new file mode 100644
index 000000000..5667d3d61
--- /dev/null
+++ b/tests/CMakeLists.txt
@@ -0,0 +1,29 @@
+# This file sets up CTest unit tests for fv3atm.
+#
+# Alex Richert, Jan 2024
+
+# Stage test data
+execute_process(COMMAND cmake -E create_symlink
+  "${CMAKE_CURRENT_SOURCE_DIR}/data"
+  "${CMAKE_CURRENT_BINARY_DIR}/data"
+  )
+
+function(add_fv3atm_mpi_test TESTNAME)
+  add_executable(${TESTNAME} ${TESTNAME}.F90)
+  target_link_libraries(${TESTNAME} PRIVATE fv3atm MPI::MPI_Fortran PIO::PIO_Fortran)
+  add_test(${TESTNAME} ${MPIEXEC_EXECUTABLE} -n 2 ${CMAKE_CURRENT_BINARY_DIR}/${TESTNAME})
+endfunction()
+
+function(add_fv3atm_serial_test TESTNAME)
+  add_executable(${TESTNAME} ${TESTNAME}.F90)
+  target_link_libraries(${TESTNAME} PRIVATE fv3atm)
+  add_test(${TESTNAME} ${CMAKE_CURRENT_BINARY_DIR}/${TESTNAME})
+endfunction()
+
+#foreach(testname test_write_netcdf)
+#  add_fv3atm_mpi_test(${testname})
+#endforeach()
+
+foreach(testname test_post_nems_routines)
+  add_fv3atm_serial_test(${testname})
+endforeach()
diff --git a/tests/data/post_namelist.nml b/tests/data/post_namelist.nml
new file mode 100644
index 000000000..262d229c7
--- /dev/null
+++ b/tests/data/post_namelist.nml
@@ -0,0 +1,20 @@
+&model_inputs
+  modelname = "DMMY"
+  submodelname = "SUBM"
+/
+&nampgb
+  kpo = 5
+  kth = 7
+  kpv = 9
+  po = 0.5 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0
+  th = 1.0 2.0 3.0 4.0 5.0 6.0 7.0
+  pv = 11. 12. 13. 14. 15. 16. 17. 18. 19.
+  hyb_sigp = F
+  d3d_on = T
+  gocart_on = T
+  popascal = T
+  rdaod = T
+  nasa_on = T
+  gccpp_on = T
+  d2d_chem = T
+/
diff --git a/tests/data/post_namelist_empty.nml b/tests/data/post_namelist_empty.nml
new file mode 100644
index 000000000..4efa4ecd5
--- /dev/null
+++ b/tests/data/post_namelist_empty.nml
@@ -0,0 +1,4 @@
+&model_inputs
+/
+&nampgb
+/
diff --git a/tests/test_post_nems_routines.F90 b/tests/test_post_nems_routines.F90
new file mode 100644
index 000000000..371c3bc8d
--- /dev/null
+++ b/tests/test_post_nems_routines.F90
@@ -0,0 +1,55 @@
+! This program provides unit testing for the subroutines in io/post_nems_routines.F90
+!
+! Alex Richert, 11 Jan 2024
+program test_post_nems_routines
+
+  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_post_nems_routines