diff --git a/tests/ocean_merge/CMakeLists.txt b/tests/ocean_merge/CMakeLists.txt
index 513f9fb57..6057e61a3 100644
--- a/tests/ocean_merge/CMakeLists.txt
+++ b/tests/ocean_merge/CMakeLists.txt
@@ -18,6 +18,9 @@ execute_process( COMMAND ${CMAKE_COMMAND} -E copy
 execute_process( COMMAND ${CMAKE_COMMAND} -E copy
     ${CMAKE_CURRENT_SOURCE_DIR}/data/oro.C48.tile1.nc ${CMAKE_CURRENT_BINARY_DIR}/oro.C48.tile1.nc)
 
+execute_process( COMMAND ${CMAKE_COMMAND} -E copy
+    ${CMAKE_CURRENT_SOURCE_DIR}/data/C48.mx500.tile1.nc ${CMAKE_CURRENT_BINARY_DIR}/C48.mx500.tile1.nc)
+
 add_executable(ftst_read_nml ftst_read_nml.F90)
 target_link_libraries(ftst_read_nml om_lib)
 
@@ -27,6 +30,10 @@ target_link_libraries(ftst_merge om_lib)
 add_executable(ftst_read_lake_mask ftst_read_lake_mask.F90)
 target_link_libraries(ftst_read_lake_mask om_lib)
 
+add_executable(ftst_read_ocean_frac ftst_read_ocean_frac.F90)
+target_link_libraries(ftst_read_ocean_frac om_lib)
+
 add_test(NAME ocean_merge-ftst_read_nml COMMAND ftst_read_nml)
 add_test(NAME ocean_merge-ftst_merge COMMAND ftst_merge)
 add_test(NAME ocean_merge-ftst_read_lake_mask COMMAND ftst_read_lake_mask)
+add_test(NAME ocean_merge-ftst_read_ocean_frac COMMAND ftst_read_ocean_frac)
diff --git a/tests/ocean_merge/data/C48.mx500.tile1.nc b/tests/ocean_merge/data/C48.mx500.tile1.nc
new file mode 100644
index 000000000..d3999075f
Binary files /dev/null and b/tests/ocean_merge/data/C48.mx500.tile1.nc differ
diff --git a/tests/ocean_merge/ftst_read_ocean_frac.F90 b/tests/ocean_merge/ftst_read_ocean_frac.F90
new file mode 100644
index 000000000..ec35621ab
--- /dev/null
+++ b/tests/ocean_merge/ftst_read_ocean_frac.F90
@@ -0,0 +1,37 @@
+! Unit test for the read_ocean_frac routine.
+!
+! Reads a 6x5 version of the ocean mask file and
+! checks values from the ocean fraction record.
+! If differences exceed a threshold, then the test fails.
+!
+ program read_ocean_info
+
+ implicit none
+
+ integer, parameter     :: lon = 6
+ integer, parameter     :: lat = 5
+ integer, parameter     :: tile = 1
+
+ character(len=3)       :: pth1="./"
+ character(len=3)       :: atmres="C48"
+ character(len=5)       :: ocnres="mx500"
+
+ real, parameter        :: thresh = 0.001
+ real                   :: ocn_frac(lon,lat)
+
+ print*,"Call routine read_ocean_frac."
+
+ call read_ocean_frac(pth1,atmres,ocnres,tile,lon,lat,ocn_frac)
+
+ print*,"Check records."
+
+ if (abs(ocn_frac(1,1)-1.0) > thresh) stop 2
+ if (abs(ocn_frac(6,5)-0.0) > thresh) stop 4
+ if (abs(ocn_frac(4,5)-0.0917) > thresh) stop 6
+ if (abs(ocn_frac(3,1)-0.162347) > thresh) stop 8
+
+ print*,"OK"
+
+ print*,"SUCCESS"
+
+ end program read_ocean_info