diff --git a/doc/specs/stdlib_strings.md b/doc/specs/stdlib_strings.md
index 5021aef15..ae348c222 100644
--- a/doc/specs/stdlib_strings.md
+++ b/doc/specs/stdlib_strings.md
@@ -283,7 +283,6 @@ Default value of `occurrence` is set to `1`.
 If `consider_overlapping` is not provided or is set to `.true.` the function counts two overlapping occurrences of substring as two different occurrences.  
 If `occurrence`th occurrence is not found, function returns `0`.
 
-
 #### Syntax
 
 `string = [[stdlib_strings(module):find(interface)]] (string, pattern [, occurrence, consider_overlapping])`
@@ -336,10 +335,9 @@ end program demo_find
 
 Format or transfer a integer/real/complex/logical variable as a character sequence.
 
-
 #### Syntax
 
-`format_string = [[stdlib_strings(module):format_string(interface)]] (value [, format])`
+`format_string = [[stdlib_strings(module):format_string(interface)]] (val [, fmt])`
 
 #### Status
 
@@ -358,33 +356,38 @@ Pure function
 
 #### Result value
 
-The result is a allocatable length Character scalar.
+The result is an allocatable length Character scalar.
 
 #### Example
 
 ```fortran
-program demo_strings_format_string
+program demo_format_string
     use, non_intrinsic :: stdlib_strings, only: format_string
     implicit none
+
     print *, 'format_string(complex) : '
         print *, format_string((1, 1))              ! (1.00000000,1.00000000)
         print *, format_string((1, 1), '(F6.2)')    ! (  1.00,  1.00)
         print *, format_string((1000, 1), '(ES0.2)'), format_string((1000, 1), '(SP,F6.3)')     ! (1.00E+3,1.00)(******,+1.000)
                         !! Too narrow formatter for real number
                         !! Normal demonstration(`******` from Fortran Standard)
+
     print *, 'format_string(integer) : '
         print *, format_string(1)                   ! 1
         print *, format_string(1, '(I4)')           !     1
         print *, format_string(1, '(I0.4)'), format_string(2, '(B4)')           ! 0001  10  
+
     print *, 'format_string(real) : '
         print *, format_string(1.)                  ! 1.00000000
         print *, format_string(1., '(F6.2)')        !   1.00 
         print *, format_string(1., '(SP,ES9.2)'), format_string(1, '(F7.3)')    ! +1.00E+00*
                         !! 1 wrong demonstration(`*` from `format_string`)
+
     print *, 'format_string(logical) : '
         print *, format_string(.true.)              ! T
         print *, format_string(.true., '(L2)')      !  T
         print *, format_string(.true., 'L2'), format_string(.false., '(I5)')    ! **
                         !! 2 wrong demonstrations(`*` from `format_string`)
-end program demo_strings_format_string
+
+end program demo_format_string
 ```
\ No newline at end of file
diff --git a/src/stdlib_strings.fypp b/src/stdlib_strings.fypp
index 6432d45df..893a8a224 100644
--- a/src/stdlib_strings.fypp
+++ b/src/stdlib_strings.fypp
@@ -18,17 +18,18 @@ module stdlib_strings
     public :: starts_with, ends_with
     public :: slice, find
 
+    !> Format other types as character sequence.
+    !> ([Specification](../page/specs/stdlib_strings.html#description))
+    !> Version: experimental
     interface format_string
-        !! version: experimental
-        !!
-        !! Format other types as character sequence.
-        !! ([Specification](../page/specs/stdlib_strings.html#description))
         #:for kind, type in KINDS_TYPES
-        pure module function format_string_${type[0]}$${kind}$(val, fmt) result(string)
-            character(len=:), allocatable :: string
+        !> Format ${type}$ variable as character sequence
+        pure module function format_string_${type[0]}$_${kind}$(val, fmt) result(string)
             ${type}$, intent(in) :: val
             character(len=*), intent(in), optional :: fmt
-        end function format_string_${type[0]}$${kind}$
+            character(len=:), allocatable :: string
+        end function format_string_${type[0]}$_${kind}$
+
         #:endfor
     end interface format_string
 
diff --git a/src/stdlib_strings_format_string.fypp b/src/stdlib_strings_format_string.fypp
index 5486acfbe..702ad9fe5 100644
--- a/src/stdlib_strings_format_string.fypp
+++ b/src/stdlib_strings_format_string.fypp
@@ -7,9 +7,11 @@ submodule (stdlib_strings) stdlib_strings_format_string
 
 contains
 
-    #:for kind, type in RIL_KINDS_TYPES
-    module procedure format_string_${type[0]}$${kind}$
-        !! Format ${type}$ variable as character sequence
+
+  #:for kind, type in RIL_KINDS_TYPES
+    !> Format ${type}$ variable as character sequence
+    module procedure format_string_${type[0]}$_${kind}$
+        
         character(len=buffer_len) :: buffer
         integer :: stat
 
@@ -21,17 +23,19 @@ contains
                 !!\TODO: *?
         end if
 
-    end procedure format_string_${type[0]}$${kind}$
-    #:endfor
+    end procedure format_string_${type[0]}$_${kind}$
+
+  #:endfor
+
+  #:for kind, type in CMPLX_KINDS_TYPES
+    !> Format ${type}$ variable as character sequence
+    module procedure format_string_${type[0]}$_${kind}$
 
-    #:for kind, type in CMPLX_KINDS_TYPES
-    module procedure format_string_${type[0]}$${kind}$
-        !! Format ${type}$ variable as character sequence
+        string = '(' // format_string_r_${kind}$(val%re, fmt) // ',' // &
+                    & format_string_r_${kind}$(val%im, fmt) // ')'
 
-        string = '('//format_string_r${kind}$(val%re, fmt)//','// &
-            format_string_r${kind}$(val%im, fmt)//')'
+    end procedure format_string_${type[0]}$_${kind}$
 
-    end procedure format_string_${type[0]}$${kind}$
-    #:endfor
+  #:endfor
 
 end submodule stdlib_strings_format_string
diff --git a/src/tests/string/CMakeLists.txt b/src/tests/string/CMakeLists.txt
index 4e5db15e2..13ae0baab 100644
--- a/src/tests/string/CMakeLists.txt
+++ b/src/tests/string/CMakeLists.txt
@@ -5,4 +5,4 @@ ADDTEST(string_match)
 ADDTEST(string_derivedtype_io)
 ADDTEST(string_functions)
 ADDTEST(string_strip_chomp)
-ADDTEST(strings_format_string)
+ADDTEST(string_format_string)
diff --git a/src/tests/string/Makefile.manual b/src/tests/string/Makefile.manual
index 7ab5e5765..80dacbd0b 100644
--- a/src/tests/string/Makefile.manual
+++ b/src/tests/string/Makefile.manual
@@ -5,7 +5,7 @@ PROGS_SRC = test_string_assignment.f90 \
             test_string_match.f90 \
             test_string_operator.f90 \
             test_string_strip_chomp.f90 \
-            test_strings_format_string.f90
+            test_string_format_string.f90
 
 
 include ../Makefile.manual.test.mk
diff --git a/src/tests/string/test_string_format_string.f90 b/src/tests/string/test_string_format_string.f90
new file mode 100644
index 000000000..d5d43b313
--- /dev/null
+++ b/src/tests/string/test_string_format_string.f90
@@ -0,0 +1,113 @@
+! SPDX-Identifier: MIT
+module test_string_format_string
+    use stdlib_strings, only: format_string, starts_with
+    use stdlib_error, only: check
+    use stdlib_optval, only: optval
+    implicit none
+
+contains
+
+
+    subroutine check_formatter(actual, expected, description, partial)
+        character(len=*), intent(in) :: actual, expected, description
+        logical, intent(in), optional :: partial
+        logical :: stat
+        character(len=:), allocatable :: msg
+
+        if (optval(partial, .false.)) then
+            stat = starts_with(actual, expected)
+        else
+            stat = actual == expected
+        end if
+
+        if (.not. stat) then
+            msg = description // new_line("a") // &
+                & "Expected: '" // expected // "' but got '" // actual // "'"
+        else
+            print '(" - ", a, /, "   Result: ''", a, "''")', description, actual
+        end if
+
+        call check(stat, msg)
+
+    end subroutine check_formatter
+
+    subroutine test_format_string_complex
+        call check_formatter(format_string((1, 1)), "(1.0", &
+                & "Default formatter for complex number", partial=.true.)
+        call check_formatter(format_string((1, 1), '(F6.2)'), "(  1.00,  1.00)", &
+                & "Formatter for complex number")
+        call check_formatter(format_string((-1, -1), '(F6.2)'), "( -1.00, -1.00)", &
+                & "Formatter for negative complex number")
+        call check_formatter(format_string((1, 1), '(SP,F6.2)'), "( +1.00, +1.00)", &
+                & "Formatter with sign control descriptor for complex number")
+        call check_formatter(format_string((1, 1), '(F6.2)') // format_string((2, 2), '(F7.3)'), &
+                & "(  1.00,  1.00)(  2.000,  2.000)", &
+                & "Multiple formatters for complex numbers")
+
+    end subroutine test_format_string_complex
+
+    subroutine test_format_string_integer
+        call check_formatter(format_string(100), "100", &
+                & "Default formatter for integer number")
+        call check_formatter(format_string(100, '(I6)'), "   100", &
+                & "Formatter for integer number")
+        call check_formatter(format_string(100, '(I0.6)'), "000100", &
+                & "Formatter with zero padding for integer number")
+        call check_formatter(format_string(100, '(I6)') // format_string(1000, '(I7)'), &
+                & "   100   1000", "Multiple formatters for integers")
+        call check_formatter(format_string(34, '(B8)'), "  100010", &
+                & "Binary formatter for integer number")
+        call check_formatter(format_string(34, '(O0.3)'), "042", &
+                & "Octal formatter with zero padding for integer number")
+        call check_formatter(format_string(34, '(Z3)'), " 22", &
+                & "Hexadecimal formatter for integer number")
+
+    end subroutine test_format_string_integer
+
+    subroutine test_format_string_real
+        call check_formatter(format_string(100.), "100.0", &
+                & "Default formatter for real number", partial=.true.)
+        call check_formatter(format_string(100., '(F6.2)'), "100.00", &
+                & "Formatter for real number")
+        call check_formatter(format_string(289., '(E7.2)'), ".29E+03", &
+                & "Exponential formatter with rounding for real number")
+        call check_formatter(format_string(128., '(ES8.2)'), "1.28E+02", &
+                & "Exponential formatter for real number")
+    
+      ! Wrong demonstration
+        call check_formatter(format_string(-100., '(F6.2)'), "*", &
+                & "Too narrow formatter for signed real number", partial=.true.)
+        call check_formatter(format_string(1000., '(F6.3)'), "*", &
+                & "Too narrow formatter for real number", partial=.true.)
+        call check_formatter(format_string(1000., '(7.3)'), "*", &
+                & "Invalid formatter for real number", partial=.true.)
+
+    end subroutine test_format_string_real
+
+    subroutine test_format_string_logical
+        call check_formatter(format_string(.true.), "T", &
+                & "Default formatter for logcal value")
+        call check_formatter(format_string(.true., '(L2)'), " T", &
+                & "Formatter for logical value")
+        call check_formatter(format_string(.false., '(L2)') // format_string(.true., '(L5)'), &
+                & " F    T", "Multiple formatters for logical values")
+
+      ! Wrong demonstration
+        call check_formatter(format_string(.false., '(1x)'), "*", &
+                & "Invalid formatter for logical value", partial=.true.)
+
+    end subroutine test_format_string_logical
+
+
+end module test_string_format_string
+
+program tester
+    use test_string_format_string
+    implicit none
+
+    call test_format_string_complex
+    call test_format_string_integer
+    call test_format_string_logical
+    call test_format_string_real
+
+end program tester
diff --git a/src/tests/string/test_strings_format_string.f90 b/src/tests/string/test_strings_format_string.f90
deleted file mode 100644
index 9f978f45a..000000000
--- a/src/tests/string/test_strings_format_string.f90
+++ /dev/null
@@ -1,82 +0,0 @@
-program test_strings_format_string
-    use stdlib_strings, only: format_string, starts_with
-    use stdlib_error, only: check
-    use stdlib_optval, only: optval
-    implicit none
-    print *, 'format_string(complex) : '
-    call check_formatter(format_string((1, 1)), "(1.0", &
-        & "Default formatter for complex number", partial=.true.)
-    call check_formatter(format_string((1, 1), '(F6.2)'), "(  1.00,  1.00)", &
-        & "Formatter for complex number")
-    call check_formatter(format_string((-1, -1), '(F6.2)'), "( -1.00, -1.00)", &
-        & "Formatter for negative complex number")
-    call check_formatter(format_string((1, 1), '(SP,F6.2)'), "( +1.00, +1.00)", &
-        & "Formatter with sign control descriptor for complex number")
-    call check_formatter(format_string((1, 1), '(F6.2)')//format_string((2, 2), '(F7.3)'), &
-        & "(  1.00,  1.00)(  2.000,  2.000)", &
-        & "Multiple formatters for complex numbers")
-    print *, 'format_string(integer) : '
-    call check_formatter(format_string(100), "100", &
-        & "Default formatter for integer number")
-    call check_formatter(format_string(100, '(I6)'), "   100", &
-        & "Formatter for integer number")
-    call check_formatter(format_string(100, '(I0.6)'), "000100", &
-        & "Formatter with zero padding for integer number")
-    call check_formatter(format_string(100, '(I6)')//format_string(1000, '(I7)'), &
-        & "   100   1000", &
-        & "Multiple formatters for integers")
-    call check_formatter(format_string(34, '(B8)'), "  100010", &
-        & "Binary formatter for integer number")
-    call check_formatter(format_string(34, '(O0.3)'), "042", &
-        & "Octal formatter with zero padding for integer number")
-    call check_formatter(format_string(34, '(Z3)'), " 22", &
-        & "Hexadecimal formatter for integer number")
-    print *, 'format_string(real) : '
-    call check_formatter(format_string(100.), "100.0", &
-        & "Default formatter for real number", partial=.true.)
-    call check_formatter(format_string(100., '(F6.2)'), "100.00", &
-        & "Formatter for real number")
-    call check_formatter(format_string(289., '(E7.2)'), ".29E+03", &
-        & "Exponential formatter with rounding for real number")
-    call check_formatter(format_string(128., '(ES8.2)'), "1.28E+02", &
-        & "Exponential formatter for real number")
-    ! Wrong demonstration
-    call check_formatter(format_string(-100., '(F6.2)'), "*", &
-        & "Too narrow formatter for signed real number", partial=.true.)
-    call check_formatter(format_string(1000., '(F6.3)'), "*", &
-        & "Too narrow formatter for real number", partial=.true.)
-    call check_formatter(format_string(1000., '(7.3)'), "*", &
-        & "Invalid formatter for real number", partial=.true.)
-    print *, 'format_string(logical) : '
-    call check_formatter(format_string(.true.), "T", &
-        & "Default formatter for logcal value")
-    call check_formatter(format_string(.true., '(L2)'), " T", &
-        & "Formatter for logical value")
-    call check_formatter(format_string(.false., '(L2)')//format_string(.true., '(L5)'), &
-        & " F    T", &
-        & "Multiple formatters for logical values")
-    ! Wrong demonstration
-    call check_formatter(format_string(.false., '(1x)'), "*", &
-        & "Invalid formatter for logical value", partial=.true.)
-
-contains
-    subroutine check_formatter(actual, expected, description, partial)
-        character(len=*), intent(in) :: actual, expected, description
-        logical, intent(in), optional :: partial
-        logical :: stat
-        character(len=:), allocatable :: msg
-
-        if (optval(partial, .false.)) then
-            stat = starts_with(actual, expected)
-        else
-            stat = actual == expected
-        end if
-        if (.not.stat) then
-            msg = description // new_line("a") // &
-                & "Expected: '"//expected//"' but got '"//actual//"'"
-        else
-            print '(" - ", a, /, "   Result: ''", a, "''")', description, actual
-        end if
-        call check(stat, msg)
-    end subroutine check_formatter
-end program test_strings_format_string