diff --git a/cime_config/testdefs/testmods_dirs/clm/Fates/shell_commands b/cime_config/testdefs/testmods_dirs/clm/Fates/shell_commands
index 41a2342a51..3443bacef0 100644
--- a/cime_config/testdefs/testmods_dirs/clm/Fates/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/clm/Fates/shell_commands
@@ -1,2 +1,7 @@
 ./xmlchange CLM_BLDNML_OPTS="-no-megan" --append
 ./xmlchange BFBFLAG="TRUE"
+
+SRCROOT=`./xmlquery SRCROOT --value`
+. "${SRCROOT}"/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
+
+ncgen -o $FATESPARAMFILE $FATESDIR/parameter_files/fates_params_default.cdl
diff --git a/cime_config/testdefs/testmods_dirs/clm/Fates/user_nl_clm b/cime_config/testdefs/testmods_dirs/clm/Fates/user_nl_clm
index 406fb598f6..1f45d85f66 100644
--- a/cime_config/testdefs/testmods_dirs/clm/Fates/user_nl_clm
+++ b/cime_config/testdefs/testmods_dirs/clm/Fates/user_nl_clm
@@ -4,6 +4,7 @@ hist_nhtfrq       = -24
 hist_empty_htapes = .true.
 hist_ndens = 1
 fates_spitfire_mode = 1
+fates_paramfile='${SRCROOT}/src/fates/parameter_files/binaries/${CASE}-params.nc'
 hist_fincl1       = 'FATES_NCOHORTS', 'FATES_TRIMMING', 'FATES_AREA_PLANTS',
 'FATES_AREA_TREES', 'FATES_COLD_STATUS', 'FATES_GDD',
 'FATES_NCHILLDAYS', 'FATES_NCOLDDAYS', 'FATES_DAYSINCE_COLDLEAFOFF','FATES_DAYSINCE_COLDLEAFON',
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/shell_commands b/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/shell_commands
index 94a832af25..5d757df0c4 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/shell_commands
@@ -1,11 +1,8 @@
-SRCDIR=`./xmlquery SRCROOT --value`
-CASEDIR=`./xmlquery CASEROOT --value`
-FATESDIR=$SRCDIR/src/fates/
-FATESPARAMFILE=$SRCDIR/fates_params_seeddisp_4x5.nc
+SRCROOT=`./xmlquery SRCROOT --value`
+. "${SRCROOT}"/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
+CASE=`./xmlquery CASE --value`
 
-ncgen -o $FATESPARAMFILE $FATESDIR/parameter_files/fates_params_default.cdl
-
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_fraction --val 0.2 --allpfts
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_max_dist --val 2500000 --allpfts
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_pdf_scale --val 1e-05 --allpfts
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_pdf_shape --val 0.1 --allpfts
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_fraction --val 0.2 --allpfts
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_max_dist --val 2500000 --allpfts
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_pdf_scale --val 1e-05 --allpfts
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_seed_dispersal_pdf_shape --val 0.1 --allpfts
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/user_nl_clm b/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/user_nl_clm
index e8d24253c1..7b736a1511 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/user_nl_clm
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdSeedDisp/user_nl_clm
@@ -1,3 +1,2 @@
-fates_paramfile = '$SRCROOT/fates_params_seeddisp_4x5.nc'
 fates_seeddisp_cadence = 1
 hist_fincl1       = 'FATES_SEEDS_IN_GRIDCELL_PF', 'FATES_SEEDS_OUT_GRIDCELL_PF'
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/shell_commands b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/shell_commands
index 5d94e5f659..e08703f6a8 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/shell_commands
@@ -1,8 +1,3 @@
-SRCDIR=`./xmlquery SRCROOT --value`
-CASEDIR=`./xmlquery CASEROOT --value`
-FATESDIR=$SRCDIR/src/fates
-FATESPARAMFILE=$CASEDIR/fates_params_twostream.nc
-
-ncgen -o $FATESPARAMFILE $FATESDIR/parameter_files/fates_params_default.cdl
-
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_rad_model --val 2 --allpfts
+SRCROOT=`./xmlquery SRCROOT --value`
+. "${SRCROOT}"/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_rad_model --val 2 --allpfts
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/user_nl_clm b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/user_nl_clm
index cae5fc2112..8b13789179 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/user_nl_clm
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStream/user_nl_clm
@@ -1 +1 @@
-fates_paramfile = '$CASEROOT/fates_params_twostream.nc'
+
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/shell_commands b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/shell_commands
index 5d94e5f659..e08703f6a8 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/shell_commands
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/shell_commands
@@ -1,8 +1,3 @@
-SRCDIR=`./xmlquery SRCROOT --value`
-CASEDIR=`./xmlquery CASEROOT --value`
-FATESDIR=$SRCDIR/src/fates
-FATESPARAMFILE=$CASEDIR/fates_params_twostream.nc
-
-ncgen -o $FATESPARAMFILE $FATESDIR/parameter_files/fates_params_default.cdl
-
-$FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_rad_model --val 2 --allpfts
+SRCROOT=`./xmlquery SRCROOT --value`
+. "${SRCROOT}"/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
+python $FATESDIR/tools/modify_fates_paramfile.py --O --fin $FATESPARAMFILE --fout $FATESPARAMFILE --var fates_rad_model --val 2 --allpfts
diff --git a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/user_nl_clm b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/user_nl_clm
index 362dfa4a5e..ffcc5dd2f5 100644
--- a/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/user_nl_clm
+++ b/cime_config/testdefs/testmods_dirs/clm/FatesColdTwoStreamNoCompFixedBioGeo/user_nl_clm
@@ -1,2 +1 @@
-fates_paramfile = '$CASEROOT/fates_params_twostream.nc'
-use_fates_fixed_biogeog=.true.
\ No newline at end of file
+use_fates_fixed_biogeog=.true.
diff --git a/cime_config/testdefs/testmods_dirs/clm/_scripts/README b/cime_config/testdefs/testmods_dirs/clm/_scripts/README
new file mode 100644
index 0000000000..66eb22a375
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/clm/_scripts/README
@@ -0,0 +1,2 @@
+This directory contains scripts that can be called in
+shell_commands of multiple testmods.
diff --git a/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh b/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
new file mode 100755
index 0000000000..382fb4e53e
--- /dev/null
+++ b/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
@@ -0,0 +1,11 @@
+# This script should be called in shell_commands with
+#    . "${SRCROOT}"/cime_config/testdefs/testmods_dirs/clm/_scripts/get_fates_shell_commands_vars.sh
+# where the leading period ensures it's run in the same shell.
+
+CASE=`./xmlquery CASE --value`
+FATESDIR="${SRCROOT}/src/fates"
+FATESPARAMDIR="${SRCROOT}/src/fates/parameter_files/binaries"
+mkdir -p "${FATESPARAMDIR}"
+FATESPARAMFILE="${FATESPARAMDIR}/${CASE}-params.nc"
+
+# No exit status because it should be called in the same shell.
diff --git a/python/ctsm/run_sys_tests.py b/python/ctsm/run_sys_tests.py
index de93081504..ce9f827b31 100644
--- a/python/ctsm/run_sys_tests.py
+++ b/python/ctsm/run_sys_tests.py
@@ -717,7 +717,8 @@ def _get_testmod_list(test_attributes, unique=False):
     for test_attribute in test_attributes:
         for dot_split in test_attribute.split("."):
             slash_replaced = dot_split.replace("/", "-")
-            for ddash_split in slash_replaced.split("--"):
+            newline_replaced = slash_replaced.replace("\n", "")
+            for ddash_split in newline_replaced.split("--"):
                 if "clm-" in ddash_split and (ddash_split not in testmods or not unique):
                     testmods.append(ddash_split)
 
@@ -744,7 +745,11 @@ def _check_py_env(test_attributes):
             raise ModuleNotFoundError("modify_fsurdat" + err_msg) from err
 
     # Check that list for any testmods that use modify_fates_paramfile.py
-    testmods_to_check = ["clm-FatesColdTwoStream", "clm-FatesColdTwoStreamNoCompFixedBioGeo"]
+    testmods_to_check = [
+        "clm-FatesColdSeedDisp",
+        "clm-FatesColdTwoStream",
+        "clm-FatesColdTwoStreamNoCompFixedBioGeo",
+    ]
     testmods = _get_testmod_list(test_attributes)
     if any(t in testmods_to_check for t in testmods):
         # This bit is needed because it's outside the top-level python/ directory.