diff --git a/tests/30mmap.tests b/tests/30mmap.tests
new file mode 100644
index 000000000..66bc7b69a
--- /dev/null
+++ b/tests/30mmap.tests
@@ -0,0 +1,36 @@
+TESTING "File mmaping" ./test-filemmap
+
+
+TEST "chunksize not initialized" mmap_missing_chunksize <<END
+return: 0
+END
+
+
+TEST "mmap not released should fail" mmap_forget_releasing <<END
+return: 134
+END
+
+
+TEST "basic mmap" mmap_simple <<END
+return: 0
+END
+
+
+TEST "use mmap twice" mmap_checkout_twice <<END
+return: 0
+END
+
+
+TEST "reuse mmap" mmap_checkout_again <<END
+return: 0
+END
+
+
+TEST "grow file" mmap_grow_existing_file <<END
+return: 0
+END
+
+
+TEST "readonly file" mmap_readonly_file <<END
+return: 0
+END
diff --git a/tests/backend/test-filemmap.c b/tests/backend/test-filemmap.c
index 1efe588d4..6e7710520 100644
--- a/tests/backend/test-filemmap.c
+++ b/tests/backend/test-filemmap.c
@@ -24,6 +24,7 @@
 
 #include "lib/llist.h"
 
+#include "backend/config.h"
 #include "backend/backend.h"
 #include "backend/file.h"
 #include "backend/filedescriptor.h"
@@ -32,12 +33,100 @@
 
 #include "tests/test.h"
 
+#include <unistd.h>
+#include <errno.h>
+#include <sys/mman.h>
+
 TESTS_BEGIN
 
-TEST ("detail_usage")
+/*
+  The first two are not really tests, but some code to check for
+  filesystem and kernel semantics which might be moved elsewhere someday
+*/
+TEST ("mmap_semantic")
 {
+  int fd = open (",mmaptest", O_RDWR|O_CREAT, 0666);
+  printf ("got fd %d\n", fd);
+  printf ("error %s\n", strerror (errno));
+  ftruncate (fd, 8192);
+
+  void* addr = mmap (NULL,
+                     8192,
+                     PROT_WRITE,
+                     MAP_SHARED,
+                     fd,
+                     0);
+
+  printf ("mapped at %p\n", addr);
+  printf ("error %s\n", strerror (errno));
+
+  int i = 0;
+  while (++i && ! errno)
+    {
+      addr = mmap (NULL,
+                   4096,
+                   PROT_READ|PROT_WRITE,
+                   MAP_SHARED,
+                   fd,
+                   0);
+
+      printf ("mapped %d again %p\n", i, addr);
+      printf ("error %s\n", strerror (errno));
+    }
+}
+
+TEST ("fd_semantic")
+{
+  mkdir (",testdir", 0777); errno = 0;
+
+  int i = 0;
+  while (++i && ! errno)
+    {
+      char name[256];
+
+      sprintf (name, ",testdir/file_%d", i);
+      int fd = open (name, O_RDWR|O_CREAT, 0666);
+      printf ("#%d opened %d\n", i, fd);
+      printf ("error %s\n", strerror (errno));
+
+      void* addr = mmap (NULL,
+                         8192,
+                         PROT_WRITE,
+                         MAP_SHARED,
+                         fd,
+                         0);
+      printf ("mapped at %p\n", addr);
+
+      close (fd);
+    }
+
+}
+
+
+TEST ("mmap_missing_chunksize")
+{
+  lumiera_config_init ("./");
   lumiera_backend_init ();
-  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE, 4096);
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  if (!mmaps)
+    fprintf (stderr, "%s\n", lumiera_error());
+
+  lumiera_file_delete (file);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}
+
+
+TEST ("mmap_forget_releasing")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE);
+  lumiera_file_chunksize_set (file, 4096);
 
   LumieraMMapings mmaps = lumiera_file_mmapings (file);
 
@@ -45,16 +134,166 @@ TEST ("detail_usage")
   llist_init (&user);
 
   LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
+ 
+  (void) mmap;  //lumiera_mmapings_release_mmap (mmaps, &user, mmap);
 
+  lumiera_file_delete (file);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}
+
+
+TEST ("mmap_simple")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE);
+  lumiera_file_chunksize_set (file, 4096);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  llist user;
+  llist_init (&user);
+  LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
 
   lumiera_mmapings_release_mmap (mmaps, &user, mmap);
 
   lumiera_file_delete (file);
+
+  /* check that the file got truncated to the desired size */
+  struct stat st;
+  stat (",tmp-filemmap", &st);
+  ENSURE (st.st_size == 100);
+
   lumiera_backend_destroy ();
+  lumiera_config_destroy ();
 }
 
 
 
+TEST ("mmap_checkout_twice")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE);
+  lumiera_file_chunksize_set (file, 4096);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  llist user;
+  llist_init (&user);
+  LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
+
+  llist user2;
+  llist_init (&user2);
+  LumieraMMap mmap2 = lumiera_mmapings_mmap_acquire (mmaps, file, &user2, 0, 100);
+
+  ENSURE (lumiera_mmap_address (mmap) == lumiera_mmap_address (mmap2));
+
+  lumiera_mmapings_release_mmap (mmaps, &user, mmap);
+
+  lumiera_mmapings_release_mmap (mmaps, &user2, mmap2);
+
+  lumiera_file_delete (file);
+
+  /* check that the file got truncated to the desired size */
+  struct stat st;
+  stat (",tmp-filemmap", &st);
+  ENSURE (st.st_size == 100);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}
+
+
+
+TEST ("mmap_checkout_again")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_CREATE);
+  lumiera_file_chunksize_set (file, 4096);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  llist user;
+  llist_init (&user);
+  LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
+  lumiera_mmapings_release_mmap (mmaps, &user, mmap);
+
+  llist user2;
+  llist_init (&user2);
+  LumieraMMap mmap2 = lumiera_mmapings_mmap_acquire (mmaps, file, &user2, 0, 100);
+  lumiera_mmapings_release_mmap (mmaps, &user2, mmap2);
+
+  lumiera_file_delete (file);
+
+  /* check that the file got truncated to the desired size */
+  struct stat st;
+  stat (",tmp-filemmap", &st);
+  ENSURE (st.st_size == 100);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}
+
+
+
+TEST ("mmap_grow_existing_file")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_READWRITE);
+
+  lumiera_file_chunksize_set (file, 4096);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  llist user;
+  llist_init (&user);
+
+  LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
+  lumiera_mmapings_release_mmap (mmaps, &user, mmap);
+
+  lumiera_file_delete (file);
+
+  /* check that the file got truncated to the desired size */
+  struct stat st;
+  stat (",tmp-filemmap", &st);
+  ENSURE (st.st_size == 100);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}
+
+
+TEST ("mmap_readonly_file")
+{
+  lumiera_config_init ("./");
+  lumiera_backend_init ();
+  LumieraFile file = lumiera_file_new (",tmp-filemmap", LUMIERA_FILE_READONLY);
+
+  lumiera_file_chunksize_set (file, 4096);
+
+  LumieraMMapings mmaps = lumiera_file_mmapings (file);
+
+  llist user;
+  llist_init (&user);
+
+  LumieraMMap mmap = lumiera_mmapings_mmap_acquire (mmaps, file, &user, 0, 100);
+  lumiera_mmapings_release_mmap (mmaps, &user, mmap);
+
+  lumiera_file_delete (file);
+
+  /* check that the file got truncated to the desired size */
+  struct stat st;
+  stat (",tmp-filemmap", &st);
+  ENSURE (st.st_size == 100);
+
+  lumiera_backend_destroy ();
+  lumiera_config_destroy ();
+}