diff --git a/test/unit/fortran/src/core_utils/test_string_core_utils.pf b/test/unit/fortran/src/core_utils/test_string_core_utils.pf
index 50a8b99e..1498ed76 100644
--- a/test/unit/fortran/src/core_utils/test_string_core_utils.pf
+++ b/test/unit/fortran/src/core_utils/test_string_core_utils.pf
@@ -72,7 +72,7 @@ subroutine test_stringify_empty_arrays()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(128), allocatable :: carr(:)
+    character(len=128), allocatable :: carr(:)
     integer(int32), allocatable :: i32arr(:)
     integer(int64), allocatable :: i64arr(:)
     logical, allocatable :: larr(:)
@@ -95,20 +95,20 @@ subroutine test_stringify_character_array()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator = '<'
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_default_separator = &
+    character(len=*), parameter :: custom_separator = '<'
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_default_separator = &
         'Talc, Gypsum, Calcite, Fluorite, Apatite, Orthoclase, Quartz, Topaz, Corundum, Diamond'
-    character(*), parameter :: expected_custom_separator = &
+    character(len=*), parameter :: expected_custom_separator = &
         'Talc<Gypsum<Calcite<Fluorite<Apatite<Orthoclase<Quartz<Topaz<Corundum<Diamond'
-    character(*), parameter :: expected_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_custom_separator_with_spaces = &
         'Talc < Gypsum < Calcite < Fluorite < Apatite < Orthoclase < Quartz < Topaz < Corundum < Diamond'
 
-    character(128), allocatable :: carr(:)
+    character(len=128), allocatable :: carr(:)
 
     allocate(carr(10))
 
-    carr(:) = [ character(len(carr)) :: &
+    carr(:) = [ character(len=len(carr)) :: &
         '      Talc', 'Gypsum', 'Calcite', 'Fluorite', 'Apatite', &
         'Orthoclase', 'Quartz', '  Topaz', 'Corundum', 'Diamond' ]
 
@@ -126,13 +126,13 @@ subroutine test_stringify_integer_array()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator = '<'
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_default_separator = &
+    character(len=*), parameter :: custom_separator = '<'
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_default_separator = &
         '-10000, -1000, -100, -10, -1, 1, 10, 100, 1000, 10000'
-    character(*), parameter :: expected_custom_separator = &
+    character(len=*), parameter :: expected_custom_separator = &
         '-10000<-1000<-100<-10<-1<1<10<100<1000<10000'
-    character(*), parameter :: expected_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_custom_separator_with_spaces = &
         '-10000 < -1000 < -100 < -10 < -1 < 1 < 10 < 100 < 1000 < 10000'
 
     integer(int32), allocatable :: i32arr(:)
@@ -160,14 +160,14 @@ subroutine test_stringify_integer_extreme_values()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_int32_default_separator = &
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_int32_default_separator = &
         '-2147483647, -1000, -100, -10, -1, 1, 10, 100, 1000, 2147483647'
-    character(*), parameter :: expected_int64_default_separator = &
+    character(len=*), parameter :: expected_int64_default_separator = &
         '-9223372036854775807, -1000, -100, -10, -1, 1, 10, 100, 1000, 9223372036854775807'
-    character(*), parameter :: expected_int32_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_int32_custom_separator_with_spaces = &
         '-2147483647 < -1000 < -100 < -10 < -1 < 1 < 10 < 100 < 1000 < 2147483647'
-    character(*), parameter :: expected_int64_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_int64_custom_separator_with_spaces = &
         '-9223372036854775807 < -1000 < -100 < -10 < -1 < 1 < 10 < 100 < 1000 < 9223372036854775807'
 
     integer(int32), allocatable :: i32arr(:)
@@ -193,15 +193,15 @@ subroutine test_stringify_floating_point_array()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator = '<'
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_default_separator = &
+    character(len=*), parameter :: custom_separator = '<'
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_default_separator = &
         '-10000.000000,  -1000.000000,   -100.000000,    -10.000000,     -1.000000, ' // &
         '     1.000000,     10.000000,    100.000000,   1000.000000,  10000.000000'
-    character(*), parameter :: expected_custom_separator = &
+    character(len=*), parameter :: expected_custom_separator = &
         '-10000.000000< -1000.000000<  -100.000000<   -10.000000<    -1.000000<' // &
         '     1.000000<    10.000000<   100.000000<  1000.000000< 10000.000000'
-    character(*), parameter :: expected_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_custom_separator_with_spaces = &
         '-10000.000000 <  -1000.000000 <   -100.000000 <    -10.000000 <     -1.000000 < ' // &
         '     1.000000 <     10.000000 <    100.000000 <   1000.000000 <  10000.000000'
 
@@ -231,11 +231,11 @@ subroutine test_stringify_floating_point_scientific_notation()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_default_separator = &
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_default_separator = &
         '-1.000000E+05, -1.000000E+03, -1.000000E+02, -1.000000E+01, -1.000000E+00, ' // &
         ' 1.000000E+00,  1.000000E+01,  1.000000E+02,  1.000000E+03,  1.000000E+05'
-    character(*), parameter :: expected_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_custom_separator_with_spaces = &
         '-1.000000E+05 < -1.000000E+03 < -1.000000E+02 < -1.000000E+01 < -1.000000E+00 < ' // &
         ' 1.000000E+00 <  1.000000E+01 <  1.000000E+02 <  1.000000E+03 <  1.000000E+05'
 
@@ -260,17 +260,17 @@ subroutine test_stringify_floating_point_extreme_values()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator_with_spaces = ' < '
-    character(*), parameter :: expected_real32_default_separator = &
+    character(len=*), parameter :: custom_separator_with_spaces = ' < '
+    character(len=*), parameter :: expected_real32_default_separator = &
         '-3.402823E+38, -1.000000E+03, -1.000000E+02, -1.000000E+01, -1.000000E+00, ' // &
         ' 1.000000E+00,  1.000000E+01,  1.000000E+02,  1.000000E+03,  3.402823E+38'
-    character(*), parameter :: expected_real64_default_separator = &
+    character(len=*), parameter :: expected_real64_default_separator = &
         '-9.999999E+99, -1.000000E+03, -1.000000E+02, -1.000000E+01, -1.000000E+00, ' // &
         ' 1.000000E+00,  1.000000E+01,  1.000000E+02,  1.000000E+03,  9.999999E+99'
-    character(*), parameter :: expected_real32_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_real32_custom_separator_with_spaces = &
         '-3.402823E+38 < -1.000000E+03 < -1.000000E+02 < -1.000000E+01 < -1.000000E+00 < ' // &
         ' 1.000000E+00 <  1.000000E+01 <  1.000000E+02 <  1.000000E+03 <  3.402823E+38'
-    character(*), parameter :: expected_real64_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_real64_custom_separator_with_spaces = &
         '-9.999999E+99 < -1.000000E+03 < -1.000000E+02 < -1.000000E+01 < -1.000000E+00 < ' // &
         ' 1.000000E+00 <  1.000000E+01 <  1.000000E+02 <  1.000000E+03 <  9.999999E+99'
 
@@ -296,13 +296,13 @@ subroutine test_stringify_logical_array()
     use funit
     use string_core_utils, only: core_stringify
 
-    character(*), parameter :: custom_separator = '.or.'
-    character(*), parameter :: custom_separator_with_spaces = ' .or. '
-    character(*), parameter :: expected_default_separator = &
+    character(len=*), parameter :: custom_separator = '.or.'
+    character(len=*), parameter :: custom_separator_with_spaces = ' .or. '
+    character(len=*), parameter :: expected_default_separator = &
         'T, F, T, F, T, F, T, F, T, F'
-    character(*), parameter :: expected_custom_separator = &
+    character(len=*), parameter :: expected_custom_separator = &
         'T.or.F.or.T.or.F.or.T.or.F.or.T.or.F.or.T.or.F'
-    character(*), parameter :: expected_custom_separator_with_spaces = &
+    character(len=*), parameter :: expected_custom_separator_with_spaces = &
         'T .or. F .or. T .or. F .or. T .or. F .or. T .or. F .or. T .or. F'
 
     logical, allocatable :: larr(:)