diff --git a/testsuite/tests/hash/test.yaml b/testsuite/tests/hash/test.yaml
index fde3f872..c944e34a 100644
--- a/testsuite/tests/hash/test.yaml
+++ b/testsuite/tests/hash/test.yaml
@@ -1,4 +1,5 @@
 description: Basic GNATCOLL.Hash test
+timeout: 500 # Default time is not enough for the valgrind run
 control:
     - [SKIP, "env.target.machine == 'qemu'",
        "Not enough disk space on cross qemu configuration"]
diff --git a/testsuite/tests/paragraph_filling/text/test.adb b/testsuite/tests/paragraph_filling/text/test.adb
index f5be952e..2f644cee 100644
--- a/testsuite/tests/paragraph_filling/text/test.adb
+++ b/testsuite/tests/paragraph_filling/text/test.adb
@@ -35,10 +35,10 @@ function Test return Integer is
 
    subtype Acc is GNAT.Strings.String_Access;
 
-   S_In : constant Acc := Read_File (Create_From_Base ("in.txt"));
-   S_Gr : constant Acc := Read_File (Create_From_Base ("greedy.txt"));
-   S_Pr : constant Acc := Read_File (Create_From_Base ("pretty.txt"));
-   S_Kn : constant Acc := Read_File (Create_From_Base ("knuth.txt"));
+   S_In : Acc := Read_File (Create_From_Base ("in.txt"));
+   S_Gr : Acc := Read_File (Create_From_Base ("greedy.txt"));
+   S_Pr : Acc := Read_File (Create_From_Base ("pretty.txt"));
+   S_Kn : Acc := Read_File (Create_From_Base ("knuth.txt"));
 
 begin
 
@@ -58,5 +58,10 @@ begin
    A.Assert (S_Kn.all, ASU.To_String (Knuth_Fill (S_In.all, 60)),
              "Knuth fill");
 
+   GNAT.Strings.Free (S_In);
+   GNAT.Strings.Free (S_Gr);
+   GNAT.Strings.Free (S_Pr);
+   GNAT.Strings.Free (S_Kn);
+
    return A.Report;
 end Test;
diff --git a/testsuite/tests/promises/test.adb b/testsuite/tests/promises/test.adb
index bee58576..4862644d 100644
--- a/testsuite/tests/promises/test.adb
+++ b/testsuite/tests/promises/test.adb
@@ -24,6 +24,7 @@
 with Ada.Text_IO;            use Ada.Text_IO;
 with GNATCOLL.Promises;      use GNATCOLL.Promises;
 with Test_Promises_Support;  use Test_Promises_Support;
+with Ada.Strings.Unbounded;  use Ada.Strings.Unbounded;
 
 with Test_Assert;
 
@@ -64,7 +65,7 @@ begin
                 and new Convert_Float
                 and new Display_String);
    Put_Line ("Failing...");
-   Message := new String'("Explicit failure");
+   Message := To_Unbounded_String ("Explicit failure");
    P.Set_Error ("Explicit failure");
    A.Assert (A.Assert_Count, 7, "expected number of asserts #2");
 
@@ -74,7 +75,8 @@ begin
                 and new Fail_On_Float
                 and (new Display_String & new Display_String));
    Baseline := 3;
-   Message := new String'("explicit");
+
+   Message := To_Unbounded_String ("explicit");
    P.Set_Value (3);
    A.Assert (A.Assert_Count, 11, "expected number of asserts #3");
 
diff --git a/testsuite/tests/promises/test_promises_support.adb b/testsuite/tests/promises/test_promises_support.adb
index 933a49f9..6ab8fcf8 100644
--- a/testsuite/tests/promises/test_promises_support.adb
+++ b/testsuite/tests/promises/test_promises_support.adb
@@ -80,7 +80,7 @@ package body Test_Promises_Support is
       pragma Unreferenced (Self);
    begin
       Put_Line ("Display_String.Failed because " & Reason);
-      A.Assert (Reason, Message.all, "expected reason");
+      A.Assert (Reason, To_String (Message), "expected reason");
    end On_Error;
 
    overriding procedure On_Next
diff --git a/testsuite/tests/promises/test_promises_support.ads b/testsuite/tests/promises/test_promises_support.ads
index 72404a8a..4886962f 100644
--- a/testsuite/tests/promises/test_promises_support.ads
+++ b/testsuite/tests/promises/test_promises_support.ads
@@ -22,11 +22,12 @@
 ------------------------------------------------------------------------------
 
 with GNATCOLL.Promises; use GNATCOLL.Promises;
+with Ada.Strings.Unbounded; use Ada.Strings.Unbounded;
 
 package Test_Promises_Support is
 
    Baseline : Integer := 0;
-   Message : access String;
+   Message : Unbounded_String;
    --  Values that Assert routines should verify
 
    package Int_Promises is new Promises (Integer);
diff --git a/testsuite/tests/vfs/basic/test.adb b/testsuite/tests/vfs/basic/test.adb
index 30d999bb..25b17430 100644
--- a/testsuite/tests/vfs/basic/test.adb
+++ b/testsuite/tests/vfs/basic/test.adb
@@ -72,7 +72,17 @@ function Test return Integer is
       Write (W, "first word ");
       Close (W);
       W := Write_File (F, Append => True);
-      Write (W, Interfaces.C.Strings.New_String ("second word"));
+
+      declare
+         use Interfaces.C.Strings;
+
+         C_String : chars_ptr :=
+           Interfaces.C.Strings.New_String ("second word");
+      begin
+         Write (W, C_String);
+         Free (C_String);
+      end;
+
       Close (W);
 
       --  Check whether the file exists