diff --git a/runners/test_runner.c b/runners/test_runner.c
index b4ee92a5..423bd1b7 100644
--- a/runners/test_runner.c
+++ b/runners/test_runner.c
@@ -859,9 +859,10 @@ static void summary(void) {
     char perm_buf[64];
     sprintf(perm_buf, "%zu/%zu", perms.filtered, perms.total);
     char flag_buf[64];
-    sprintf(flag_buf, "%s%s%s",
-            (flags & TEST_REENTRANT) ? "r" : "",
+    sprintf(flag_buf, "%s%s%s%s",
             (flags & TEST_INTERNAL)  ? "i" : "",
+            (flags & TEST_REENTRANT) ? "r" : "",
+            (flags & TEST_FUZZ)      ? "f" : "",
             (!flags)                 ? "-" : "");
     printf("%-23s  %7s %7zu %7zu %15s\n",
             "TOTAL",
@@ -918,9 +919,10 @@ static void list_suites(void) {
             char perm_buf[64];
             sprintf(perm_buf, "%zu/%zu", perms.filtered, perms.total);
             char flag_buf[64];
-            sprintf(flag_buf, "%s%s%s",
-                    (test_suites[i]->flags & TEST_REENTRANT) ? "r" : "",
+            sprintf(flag_buf, "%s%s%s%s",
                     (test_suites[i]->flags & TEST_INTERNAL)  ? "i" : "",
+                    (test_suites[i]->flags & TEST_REENTRANT) ? "r" : "",
+                    (test_suites[i]->flags & TEST_FUZZ)      ? "f" : "",
                     (!test_suites[i]->flags)                 ? "-" : "");
             printf("%-*s  %7s %7zu %15s\n",
                     name_width,
@@ -971,11 +973,13 @@ static void list_cases(void) {
                 char perm_buf[64];
                 sprintf(perm_buf, "%zu/%zu", perms.filtered, perms.total);
                 char flag_buf[64];
-                sprintf(flag_buf, "%s%s%s",
-                        (test_suites[i]->cases[j].flags & TEST_REENTRANT)
-                            ? "r" : "",
+                sprintf(flag_buf, "%s%s%s%s",
                         (test_suites[i]->cases[j].flags & TEST_INTERNAL)
                             ? "i" : "",
+                        (test_suites[i]->cases[j].flags & TEST_REENTRANT)
+                            ? "r" : "",
+                        (test_suites[i]->cases[j].flags & TEST_FUZZ)
+                            ? "f" : "",
                         (!test_suites[i]->cases[j].flags)
                             ? "-" : "");
                 printf("%-*s  %7s %15s\n",
diff --git a/runners/test_runner.h b/runners/test_runner.h
index a2e3c3f0..cf271f23 100644
--- a/runners/test_runner.h
+++ b/runners/test_runner.h
@@ -35,6 +35,7 @@ struct lfs_config;
 enum test_flags {
     TEST_INTERNAL  = 0x1,
     TEST_REENTRANT = 0x2,
+    TEST_FUZZ      = 0x4,
 };
 typedef uint8_t test_flags_t;
 
diff --git a/scripts/test.py b/scripts/test.py
index ab62c395..bbce9a17 100755
--- a/scripts/test.py
+++ b/scripts/test.py
@@ -59,10 +59,13 @@ class TestCase:
         self.code_lineno = config.pop('code_lineno', None)
         self.in_ = config.pop('in',
             config.pop('suite_in', None))
+        self.fuzz_ = config.pop('fuzz',
+            config.pop('suite_fuzz', None))
 
         self.internal = bool(self.in_)
         self.reentrant = config.pop('reentrant',
             config.pop('suite_reentrant', False))
+        self.fuzz = bool(self.fuzz_)
 
         # figure out defines and build possible permutations
         self.defines = set()
@@ -207,6 +210,7 @@ class TestSuite:
                     if not case_linenos or l < case_linenos[0][0]),
                 default=None)
             self.in_ = config.pop('in', None)
+            self.fuzz_ = config.pop('fuzz', None)
 
             self.after = config.pop('after', [])
             if not isinstance(self.after, list):
@@ -226,6 +230,7 @@ class TestSuite:
                     'suite_defines': defines,
                     'suite_in': self.in_,
                     'suite_reentrant': reentrant,
+                    'suite_fuzz': self.fuzz_,
                     **case},
                     args=args))
 
@@ -239,6 +244,7 @@ class TestSuite:
             # combine other per-case things
             self.internal = any(case.internal for case in self.cases)
             self.reentrant = any(case.reentrant for case in self.cases)
+            self.fuzz = any(case.fuzz for case in self.cases)
 
         for k in config.keys():
             print('%swarning:%s in %s, found unused key %r' % (
@@ -464,7 +470,8 @@ def compile(test_paths, **args):
                 f.writeln(4*' '+'.flags = %s,'
                     % (' | '.join(filter(None, [
                         'TEST_INTERNAL' if suite.internal else None,
-                        'TEST_REENTRANT' if suite.reentrant else None]))
+                        'TEST_REENTRANT' if suite.reentrant else None,
+                        'TEST_FUZZ' if suite.fuzz else None]))
                         or 0))
                 # create suite defines
                 if suite.defines:
@@ -484,7 +491,8 @@ def compile(test_paths, **args):
                         f.writeln(12*' '+'.flags = %s,'
                             % (' | '.join(filter(None, [
                                 'TEST_INTERNAL' if case.internal else None,
-                                'TEST_REENTRANT' if case.reentrant else None]))
+                                'TEST_REENTRANT' if case.reentrant else None,
+                                'TEST_FUZZ' if case.fuzz else None]))
                                 or 0))
                         # create case defines
                         if case.defines:
diff --git a/tests/test_badblocks.toml b/tests/test_badblocks.toml
index 1108358d..f739d8e1 100644
--- a/tests/test_badblocks.toml
+++ b/tests/test_badblocks.toml
@@ -16,9 +16,10 @@ defines.BADBLOCK_BEHAVIOR = [
 #    'LFS_EMUBD_BADBLOCK_ERASENOOP',
 ]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
-defines.SEED = 42
 # maximize lookahead buffer to avoid alloc scans
 defines.LOOKAHEAD_SIZE = 'lfs_alignup(BLOCK_COUNT / 8, 8)'
+defines.SEED = 42
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     // test all possible bad blocks
@@ -122,9 +123,10 @@ defines.BADBLOCK_BEHAVIOR = [
 ]
 defines.MIRROR = [false, true]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
-defines.SEED = 42
 # maximize lookahead buffer to avoid alloc scans
 defines.LOOKAHEAD_SIZE = 'lfs_alignup(BLOCK_COUNT / 8, 8)'
+defines.SEED = 42
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     // test a large region of bad blocks
@@ -225,9 +227,10 @@ defines.BADBLOCK_BEHAVIOR = [
 ]
 defines.MIRROR = [false, true]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
-defines.SEED = 42
 # maximize lookahead buffer to avoid alloc scans
 defines.LOOKAHEAD_SIZE = 'lfs_alignup(BLOCK_COUNT / 8, 8)'
+defines.SEED = 42
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     // test a large region of bad blocks
@@ -333,6 +336,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 # do more ops than dirs to encourage rename collisions
 defines.OPS = '2*N'
 defines.SEED = 42
+fuzz = 'SEED'
 code = '''
     // test all possible bad blocks
     for (lfs_size_t i = 2;
@@ -463,6 +467,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 # do more ops than dirs to encourage rename collisions
 defines.OPS = '2*N'
 defines.SEED = 42
+fuzz = 'SEED'
 code = '''
     // test a large region of bad blocks
     for (lfs_size_t i = 0; i < BLOCK_COUNT/2; i++) {
@@ -594,6 +599,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 # do more ops than dirs to encourage rename collisions
 defines.OPS = '2*N'
 defines.SEED = 42
+fuzz = 'SEED'
 code = '''
     // test a large region of bad blocks
     for (lfs_size_t i = 0; i < BLOCK_COUNT/2; i++) {
@@ -735,6 +741,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test all possible bad blocks
@@ -894,6 +901,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test a large region of bad blocks
@@ -1054,6 +1062,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test a large region of bad blocks
@@ -1203,7 +1212,6 @@ defines.BADBLOCK_BEHAVIOR = [
 #    'LFS_EMUBD_BADBLOCK_ERASENOOP',
 ]
 defines.N = 20
-defines.SEED = 42
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -1220,6 +1228,8 @@ defines.CHUNK = [32, 8, 1]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 42
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1376,7 +1386,6 @@ defines.BADBLOCK_BEHAVIOR = [
 ]
 defines.MIRROR = [false, true]
 defines.N = 20
-defines.SEED = 42
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -1393,6 +1402,8 @@ defines.CHUNK = [32, 8, 1]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 42
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1550,7 +1561,6 @@ defines.BADBLOCK_BEHAVIOR = [
 ]
 defines.MIRROR = [false, true]
 defines.N = 20
-defines.SEED = 42
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -1567,6 +1577,8 @@ defines.CHUNK = [32, 8, 1]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 42
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1736,6 +1748,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test all possible bad blocks
@@ -2177,6 +2190,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test a large region of bad blocks
@@ -2617,6 +2631,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // test a large region of bad blocks
diff --git a/tests/test_btree.toml b/tests/test_btree.toml
index 68df1d59..74f049e9 100644
--- a/tests/test_btree.toml
+++ b/tests/test_btree.toml
@@ -398,6 +398,7 @@ code = '''
 [cases.test_btree_push_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -547,6 +548,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.W = 5
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -913,6 +915,7 @@ code = '''
 [cases.test_btree_update_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -1071,6 +1074,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.W = 5
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -1664,6 +1668,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.REMAINING = [64, 2, 1, 0]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = 'N > REMAINING'
 in = 'lfs.c'
 code = '''
@@ -1857,6 +1862,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.W = 5
 defines.REMAINING = [64, 2, 1, 0]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = 'N > REMAINING'
 in = 'lfs.c'
 code = '''
@@ -2066,6 +2072,7 @@ code = '''
 [cases.test_btree_split_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -2214,6 +2221,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.W = 5
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -2669,6 +2677,7 @@ code = '''
 [cases.test_btree_general_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -2774,6 +2783,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]
 defines.W = 5
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -3324,6 +3334,7 @@ code = '''
 [cases.test_btree_find_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -3511,6 +3522,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.W = 5
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -3666,6 +3678,7 @@ code = '''
 [cases.test_btree_find_general_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -3822,6 +3835,7 @@ code = '''
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024]
 defines.W = 5
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -4148,6 +4162,7 @@ code = '''
 [cases.test_btree_traversal_fuzz]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256, 512]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
diff --git a/tests/test_dirs.toml b/tests/test_dirs.toml
index caafc797..44d2d256 100644
--- a/tests/test_dirs.toml
+++ b/tests/test_dirs.toml
@@ -1341,6 +1341,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.OPS = '2*N'
 defines.PARENT = [false, true]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 # limit powerloss testing due to time
 if = '!TEST_PLS || N <= 8'
 reentrant = true
@@ -4128,6 +4129,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.OPS = '2*N'
 defines.PARENT = [false, true]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 # limit powerloss testing due to time
 if = '!TEST_PLS || N <= 8'
 reentrant = true
@@ -6639,6 +6641,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.OPS = '2*N'
 defines.PARENT = [false, true]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 # limit powerloss testing due to time
 if = '!TEST_PLS || N <= 8'
 reentrant = true
@@ -6790,6 +6793,7 @@ defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.OPS = '2*N'
 defines.PARENT = [false, true]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 # limit powerloss testing due to time
 if = '!TEST_PLS || N <= 8'
 reentrant = true
diff --git a/tests/test_exhaustion.toml b/tests/test_exhaustion.toml
index 4c78947b..23a34c15 100644
--- a/tests/test_exhaustion.toml
+++ b/tests/test_exhaustion.toml
@@ -25,6 +25,7 @@ defines.ERASE_CYCLES = 10
 defines.BLOCK_RECYCLES = 4
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.SEED = 42
+fuzz = 'SEED'
 code = '''
     // run our test twice, once with 1/2 the storage, once with 2/2 the
     // storage, and compare how many operations we were able to perform
@@ -223,6 +224,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // run our test twice, once with 1/2 the storage, once with 2/2 the
@@ -484,6 +486,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // run our test twice, once with 1/2 the storage, once with 2/2 the
@@ -887,6 +890,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 42
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     // run our test twice, once with 1/2 the storage, once with 2/2 the
diff --git a/tests/test_files.toml b/tests/test_files.toml
index ee37aba8..55bf10bd 100644
--- a/tests/test_files.toml
+++ b/tests/test_files.toml
@@ -792,6 +792,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -1154,6 +1155,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -2270,6 +2272,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -2466,6 +2469,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -2686,6 +2690,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 reentrant = true
 code = '''
diff --git a/tests/test_forphans.toml b/tests/test_forphans.toml
index d4548af2..8e888cc5 100644
--- a/tests/test_forphans.toml
+++ b/tests/test_forphans.toml
@@ -6662,6 +6662,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -7000,6 +7001,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(20)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
diff --git a/tests/test_fsync.toml b/tests/test_fsync.toml
index 6d765e20..ba6abc5a 100644
--- a/tests/test_fsync.toml
+++ b/tests/test_fsync.toml
@@ -534,7 +534,6 @@ code = '''
 
 [cases.test_fsync_rrrr_fuzz]
 defines.R = 4
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -545,6 +544,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -687,7 +688,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -698,6 +698,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -873,7 +875,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -884,6 +885,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -1066,7 +1069,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1077,6 +1079,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -1279,7 +1283,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1290,6 +1293,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -1391,7 +1396,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 40
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1402,6 +1406,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -1525,7 +1531,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 40
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1536,6 +1541,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -2426,7 +2433,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -2437,6 +2443,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -2619,7 +2627,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -2630,6 +2637,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -2827,7 +2836,6 @@ defines.SYNC = [0, 1, 2]
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 20
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -2838,6 +2846,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -2944,7 +2954,6 @@ defines.RW = 4
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 40
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -2955,6 +2964,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -3093,7 +3104,6 @@ defines.RW = 4
 # FLUSH=1 => flush via lfsr_file_flush
 # FLUSH=2 => flush via LFS_O_FLUSH
 defines.FLUSH = [0, 1, 2]
-defines.SEED = 'range(20)'
 defines.N = 40
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -3104,6 +3114,8 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.CHUNK = '(SIZE+16-1) / 16'
+defines.SEED = 'range(20)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
diff --git a/tests/test_fwrite.toml b/tests/test_fwrite.toml
index c1400a01..673d5bf3 100644
--- a/tests/test_fwrite.toml
+++ b/tests/test_fwrite.toml
@@ -1524,7 +1524,6 @@ code = '''
 # fuzz testing
 [cases.test_fwrite_fuzz_aligned]
 defines.N = 20
-defines.SEED = 'range(10)'
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -1540,6 +1539,8 @@ defines.CHUNK = [32, 8, 1]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1666,7 +1667,6 @@ code = '''
 # fuzz testing
 [cases.test_fwrite_fuzz_unaligned]
 defines.N = 20
-defines.SEED = 'range(10)'
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -1683,6 +1683,8 @@ defines.CHUNK = [32, 8]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1816,7 +1818,6 @@ code = '''
 # more seek testing
 [cases.test_fwrite_r_seek]
 defines.N = 20
-defines.SEED = 'range(10)'
 defines.WHENCE = ['LFS_SEEK_SET', 'LFS_SEEK_CUR', 'LFS_SEEK_END']
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1828,6 +1829,8 @@ defines.SIZE = [
 ]
 # chunk is more an upper limit here
 defines.CHUNK = [32, 8]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -1894,7 +1897,6 @@ code = '''
 # different seek methods
 [cases.test_fwrite_w_seek]
 defines.N = 10
-defines.SEED = 'range(10)'
 defines.WHENCE = ['LFS_SEEK_SET', 'LFS_SEEK_CUR', 'LFS_SEEK_END']
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -1911,6 +1913,8 @@ defines.CHUNK = [32, 8]
 # INIT=2 => truncate to size
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -2042,7 +2046,6 @@ code = '''
 # the above was just warmup, here's the real seek test
 [cases.test_fwrite_rw_seek]
 defines.N = 10
-defines.SEED = 'range(10)'
 defines.WHENCE = ['LFS_SEEK_SET', 'LFS_SEEK_CUR', 'LFS_SEEK_END']
 defines.SIZE = [
     'FBUFFER_SIZE/2',
@@ -2059,6 +2062,8 @@ defines.CHUNK = [32, 8]
 # INIT=2 => truncate to size
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
@@ -2322,7 +2327,6 @@ code = '''
 # heavy fuzz test with rw seeks, truncate, and fruncate
 [cases.test_fwrite_rwtf_fuzz]
 defines.N = 20
-defines.SEED = 'range(10)'
 defines.SIZE = [
     'FBUFFER_SIZE/2',
     '2*FBUFFER_SIZE',
@@ -2339,6 +2343,8 @@ defines.CHUNK = [32, 8]
 defines.INIT = [0, 1, 2]
 defines.SYNC = [false, true]
 defines.REMOUNT = [false, true]
+defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = [
     'CHUNK <= SIZE',
     # this just saves testing time
diff --git a/tests/test_mtree.toml b/tests/test_mtree.toml
index bb338667..024147e1 100644
--- a/tests/test_mtree.toml
+++ b/tests/test_mtree.toml
@@ -472,6 +472,7 @@ code = '''
 defines.N = [5, 10, 20, 40, 80, 160]
 defines.FORCE_COMPACTION = [false, true]
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -1003,6 +1004,7 @@ code = '''
 defines.N = [5, 10, 20, 40, 80, 160]
 defines.FORCE_COMPACTION = [false, true]
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -2078,6 +2080,7 @@ defines.N = [5, 10, 20, 40]
 defines.FORCE_COMPACTION = [false, true]
 defines.BLOCK_RECYCLES = [4, 1, 0]
 defines.SEED = 'range(500)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
@@ -3770,6 +3773,7 @@ defines.N = [5, 10, 20, 40, 80, 160]
 defines.VALIDATE = [false, true]
 defines.FORCE_COMPACTION = [false, true]
 defines.SEED = 'range(100)'
+fuzz = 'SEED'
 in = 'lfs.c'
 code = '''
     lfs_t lfs;
diff --git a/tests/test_rbyd.toml b/tests/test_rbyd.toml
index 3af13ddc..f0f92a63 100644
--- a/tests/test_rbyd.toml
+++ b/tests/test_rbyd.toml
@@ -3998,6 +3998,7 @@ code = '''
 [cases.test_rbyd_fuzz_append_removes]
 defines.N = 'range(1, 33)'
 defines.SEED = 'range(1000)'
+fuzz = 'SEED'
 # large progs take too long for now
 if = 'PROG_SIZE < 512'
 in = 'lfs.c'
@@ -11818,6 +11819,7 @@ code = '''
 [cases.test_rbyd_fuzz_create_deletes]
 defines.N = 'range(1, 33)'
 defines.SEED = 'range(1000)'
+fuzz = 'SEED'
 # large progs take too long for now
 if = 'PROG_SIZE < 512'
 in = 'lfs.c'
@@ -14954,6 +14956,7 @@ code = '''
 defines.N = 'range(1, 33)'
 defines.M = 3
 defines.SEED = 'range(1000)'
+fuzz = 'SEED'
 # large progs take too long for now
 if = 'PROG_SIZE < 512'
 in = 'lfs.c'
@@ -15114,6 +15117,7 @@ code = '''
 defines.N = 'range(1, 33)'
 defines.W = 5
 defines.SEED = 'range(1000)'
+fuzz = 'SEED'
 # large progs take too long for now
 if = 'PROG_SIZE < 512'
 in = 'lfs.c'
diff --git a/tests/test_relocations.toml b/tests/test_relocations.toml
index 07e6d21e..3b9a7806 100644
--- a/tests/test_relocations.toml
+++ b/tests/test_relocations.toml
@@ -16,6 +16,7 @@ defines.BLOCK_RECYCLES = [4, 1, 0]
 defines.N = [1, 2, 4, 8, 16, 32, 64, 128, 256]
 defines.OPS = 1024
 defines.SEED = 'range(10)'
+fuzz = 'SEED'
 code = '''
     lfs_t lfs;
     lfsr_format(&lfs, CFG) => 0;
@@ -175,6 +176,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -387,6 +389,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -726,6 +729,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 code = '''
     lfs_t lfs;
@@ -1150,6 +1154,7 @@ defines.SIZE = [
     '4*BLOCK_SIZE',
 ]
 defines.SEED = 'range(10)'
+fuzz = 'SEED'
 if = '(SIZE*N)/BLOCK_SIZE <= 16'
 reentrant = true
 code = '''