diff --git a/fec/tests/exec/sliceok.fe b/fec/tests/exec/sliceok.fe
new file mode 100644
index 0000000..43bd34a
--- /dev/null
+++ b/fec/tests/exec/sliceok.fe
@@ -0,0 +1,14 @@
+// EXIT:9
+unit sliceok;
+
+fn total(s: []i32) -> i32 {
+    var sum: i32 = 0;
+    for v in s { sum = sum + v.^; }
+    return sum;
+}
+
+fn main() -> i32 {
+    let a: [5]i32 = [1, 2, 3, 4, 5];
+    let mid: []i32 = a[1..4];
+    return total(mid);
+}
diff --git a/fec/tests/exec/slicerng.fe b/fec/tests/exec/slicerng.fe
new file mode 100644
index 0000000..78aef2f
--- /dev/null
+++ b/fec/tests/exec/slicerng.fe
@@ -0,0 +1,11 @@
+// EXIT:3
+// OUTPUT:index out of bounds
+// NOCHECKS:0
+unit slicerng;
+
+fn main() -> i32 {
+    let a: [2]i32 = [1, 2];
+    let s: []i32 = a[0..3];
+    let n: i32 = s.n as i32;
+    return n - n;
+}
diff --git a/fec/tests/pending-backend/README.md b/fec/tests/pending-backend/README.md
deleted file mode 100644
index a653444..0000000
--- a/fec/tests/pending-backend/README.md
+++ /dev/null
@@ -1,10 +0,0 @@
-`fec/tests/pending-backend/`에 남겨둔 fixture는 현재 프론트엔드 전용 상태에서 실행할 수 없습니다.
-
-- `bounds_trap.fe` / `bounds_nocheck.fe`: 경계 검사 실패가 실제로 trap되는지,
-  `--no-checks` 플래그가 그 검사를 제거하는지 확인하는 런타임 동작 테스트입니다.
-- `ownership_drop.fe` + `ownership-drop.c`: 삽입된 `drop`/`defer`가 실제로 실행되는지 확인하는 테스트입니다.
-  `ownership-drop.c`는 해제 횟수/순서/이중 해제를 검증하는 하네스입니다.
-- `format-prop.c`: 포맷 프로퍼티 동작을 확인하는 런타임 검사입니다.
-
-이들은 코드 생성기가 없는 현재 단계에서는 실행할 수 없어서 `tests/run.py`가 건너뜁니다.
-백엔드(코드 생성기)가 돌아오면 가장 먼저 재활성화할 대상입니다.
diff --git a/fec/tests/pending-backend/bounds_nocheck.fe b/fec/tests/pending-backend/bounds_nocheck.fe
deleted file mode 100644
index e8e62f3..0000000
--- a/fec/tests/pending-backend/bounds_nocheck.fe
+++ /dev/null
@@ -1,7 +0,0 @@
-unit m3_no_checks;
-
-fn main() -> i32 {
-    let a: [2]i32 = [1, 2];
-    let x: i32 = a[2];
-    return x - x;
-}
diff --git a/fec/tests/pending-backend/bounds_trap.fe b/fec/tests/pending-backend/bounds_trap.fe
deleted file mode 100644
index ac581ee..0000000
--- a/fec/tests/pending-backend/bounds_trap.fe
+++ /dev/null
@@ -1,6 +0,0 @@
-unit m3_bounds;
-
-fn main() -> i32 {
-    let a: [2]i32 = [1, 2];
-    return a[2];
-}
diff --git a/fec/tests/pending-backend/format-prop.c b/fec/tests/pending-backend/format-prop.c
deleted file mode 100644
index 66bba1a..0000000
--- a/fec/tests/pending-backend/format-prop.c
+++ /dev/null
@@ -1,11 +0,0 @@
-#include "prop.c"
-
-int main(void)
-{
-    fe_writer w;
-    unsigned short result;
-    w.tag=2;
-    w.handle=99;
-    result=fe_m4_prop_propagate(w);
-    return result==1 ? 0 : 1;
-}
diff --git a/fec/tests/pending-backend/ownership-drop.c b/fec/tests/pending-backend/ownership-drop.c
deleted file mode 100644
index 5d3e6bb..0000000
--- a/fec/tests/pending-backend/ownership-drop.c
+++ /dev/null
@@ -1,101 +0,0 @@
-#include <stdlib.h>
-#include <stddef.h>
-
-#undef malloc
-#undef free
-
-extern void *malloc(size_t size);
-extern void free(void *p);
-
-/* `run` returns !i32, which lowers to { error, value }. */
-struct fe_result_value_9 { unsigned short e; long v; };
-extern struct fe_result_value_9 fe_m5_runtime_run(long mode);
-extern unsigned short fe_m5_runtime_conditional(unsigned char flag);
-extern unsigned short fe_m5_runtime_argument_cleanup(void);
-extern unsigned short fe_m5_runtime_owned_slice(unsigned long n);
-extern unsigned short fe_m5_runtime_replace_field(void);
-extern unsigned short fe_m5_runtime_loop_cleanup(void);
-extern unsigned short fe_m5_runtime_try_cleanup(void);
-extern unsigned short fe_m5_runtime_field_order(void);
-extern unsigned short fe_m5_runtime_defer_order(void);
-extern unsigned short fe_m5_runtime_match_cleanup(unsigned char flag);
-extern unsigned short fe_m5_runtime_close_once(void);
-extern unsigned short fe_m5_runtime_reassign_struct(void);
-
-static void *live_ptrs[64];
-static unsigned live_count;
-static unsigned alloc_count;
-static unsigned free_count;
-static unsigned double_free_count;
-static long fail_after = -1;
-static unsigned malloc_attempts;
-static int track_order;
-static void *order_ptrs[2];
-static unsigned order_allocs;
-static unsigned order_frees;
-static unsigned order_bad;
-
-void *m5_malloc(size_t size)
-{
-    void *p;
-    if (fail_after >= 0 && (long)malloc_attempts++ == fail_after) return 0;
-    p = malloc(size);
-    if (p && live_count < 64) live_ptrs[live_count++] = p;
-    if (p) ++alloc_count;
-    if (p && track_order && order_allocs < 2) order_ptrs[order_allocs++] = p;
-    return p;
-}
-
-void m5_free(void *p)
-{
-    unsigned i;
-    if (!p) return;
-    for (i = 0; i < live_count; ++i) {
-        if (live_ptrs[i] == p) {
-            if (track_order && order_frees < 2 &&
-                p != order_ptrs[1-order_frees]) ++order_bad;
-            if (track_order && order_frees < 2) ++order_frees;
-            live_ptrs[i] = live_ptrs[--live_count];
-            ++free_count;
-            free(p);
-            return;
-        }
-    }
-    ++double_free_count;
-}
-
-int main(void)
-{
-    struct fe_result_value_9 r;
-    r = fe_m5_runtime_run(0); if (r.e != 0 || r.v != 0) return 1;
-    r = fe_m5_runtime_run(1); if (r.e != 0 || r.v != 9) return 2;
-    r = fe_m5_runtime_run(2); if (r.e != 0 || r.v != 0) return 3;
-    if (fe_m5_runtime_conditional(0) != 0) return 4;
-    if (fe_m5_runtime_conditional(1) != 0) return 5;
-    if (fe_m5_runtime_argument_cleanup() != 0) return 6;
-    if (fe_m5_runtime_owned_slice(17) != 0) return 7;
-    if (fe_m5_runtime_replace_field() != 0) return 8;
-    if (fe_m5_runtime_loop_cleanup() != 0) return 9;
-    fail_after=1;
-    malloc_attempts=0;
-    if (fe_m5_runtime_try_cleanup() == 0) return 10;
-    fail_after=-1;
-    track_order=1;
-    order_allocs=order_frees=order_bad=0;
-    if (fe_m5_runtime_field_order() != 0) return 11;
-    track_order=0;
-    if (order_allocs != 2 || order_frees != 2 || order_bad != 0) return 12;
-    track_order=1;
-    order_allocs=order_frees=order_bad=0;
-    if (fe_m5_runtime_defer_order() != 0) return 13;
-    track_order=0;
-    if (order_allocs != 2 || order_frees != 2 || order_bad != 0) return 14;
-    if (fe_m5_runtime_match_cleanup(0) != 0) return 15;
-    if (fe_m5_runtime_match_cleanup(1) != 0) return 16;
-    if (fe_m5_runtime_close_once() != 0) return 17;
-    if (fe_m5_runtime_reassign_struct() != 0) return 18;
-    if (double_free_count != 0) return 19;
-    if (live_count != 0) return 20;
-    if (alloc_count != free_count) return 21;
-    return 0;
-}
diff --git a/fec/tests/pending-backend/ownership_drop.fe b/fec/tests/pending-backend/ownership_drop.fe
deleted file mode 100644
index b9dab0c..0000000
--- a/fec/tests/pending-backend/ownership_drop.fe
+++ /dev/null
@@ -1,100 +0,0 @@
-unit m5_runtime;
-
-fn take(p: ^i32) -> void { mem.destroy(p); }
-
-pub fn run(mode: i32) -> !i32 {
-    var p: ^i32 = try mem.create(0);
-    defer { mem.destroy(p); }
-    p.^ = 7;
-    if mode == 1 {
-        p = try mem.create(0);
-        p.^ = 9;
-        return p.^;
-    }
-    while true { break; }
-    if mode == 2 { return 0; }
-    return p.^ - 7;
-}
-
-pub fn conditional(flag: bool) -> !void {
-    var p: ^i32 = try mem.create(0);
-    if flag { take(p); }
-}
-
-pub fn argument_cleanup() -> !void {
-    let p: ^i32 = try mem.create(0);
-    take(p);
-}
-
-pub fn owned_slice(n: usize) -> !void {
-    let bytes: ^[]u8 = try mem.alloc_slice(u8, n);
-}
-
-struct Holder { p: ^i32 }
-
-pub fn replace_field() -> !void {
-    let first: ^i32 = try mem.create(1);
-    var h: Holder = Holder{ p: first };
-    let second: ^i32 = try mem.create(2);
-    let old: ^i32 = mem.replace(&mut h.p, second);
-    mem.destroy(old);
-}
-
-pub fn loop_cleanup() -> !void {
-    var i: i32 = 0;
-    while i < 2 {
-        let p: ^i32 = try mem.create(i);
-        i += 1;
-        if i == 1 { continue; }
-        break;
-    }
-}
-
-pub fn try_cleanup() -> !void {
-    let first: ^i32 = try mem.create(1);
-    let second: ^i32 = try mem.create(2);
-}
-
-struct PairOwners { first: ^i32, second: ^i32 }
-
-pub fn field_order() -> !void {
-    let first: ^i32 = try mem.create(1);
-    let second: ^i32 = try mem.create(2);
-    let pair: PairOwners = PairOwners{ first: first, second: second };
-}
-
-pub fn defer_order() -> !void {
-    let first: ^i32 = try mem.create(1);
-    defer { mem.destroy(first); }
-    let second: ^i32 = try mem.create(2);
-}
-
-enum Choice { A, B }
-
-pub fn match_cleanup(flag: bool) -> !void {
-    var choice: Choice = Choice.A;
-    if flag { choice = Choice.B; }
-    let p: ^i32 = try mem.create(1);
-    match choice {
-        A => { take(p); }
-        B => { take(p); }
-    }
-}
-
-struct FileLike {
-    handle: i32,
-    fn close(self: Self) -> !void { self.handle = 0; }
-    fn drop(self: &mut Self) { self.handle = 0; }
-}
-
-pub fn close_once() -> !void {
-    let file: FileLike = FileLike{ handle: 7 };
-    try file.close();
-}
-
-pub fn reassign_struct() -> !void {
-    let first: ^i32 = try mem.create(1);
-    var owner: Holder = Holder{ p: first };
-    let second: ^i32 = try mem.create(2);
-    owner = Holder{ p: second };
-}
diff --git a/fec/tests/pending-backend/slice_bounds_trap.fe b/fec/tests/pending-backend/slice_bounds_trap.fe
deleted file mode 100644
index 89a8d88..0000000
--- a/fec/tests/pending-backend/slice_bounds_trap.fe
+++ /dev/null
@@ -1,7 +0,0 @@
-unit m3_slice_bounds;
-
-fn main() -> i32 {
-    let a: [2]i32 = [1, 2];
-    let s: []i32 = a[0..3];
-    return s.n as i32;
-}
diff --git a/tests/run.py b/tests/run.py
index f4d3575..4e50fdd 100644
--- a/tests/run.py
+++ b/tests/run.py
@@ -1,9 +1,8 @@
 """Run every fixture through the front end and check what it reports.
 
-The compiler is a front end now -- lexer, parser, types, ownership -- so a
-fixture is checked by running `fec` on it and looking at two things: whether it
-was accepted, and, when it was rejected, whether the diagnostic is the one the
-fixture asked for.
+A fixture is checked by running `fec` on it and looking at two things: whether
+it was accepted, and, when it was rejected, whether the diagnostic is the one
+the fixture asked for.
 
 A fixture states its expectation in its first line:
 
@@ -17,8 +16,8 @@ not pin the message yet. Anything else must be accepted.
 Fixtures under `parse/` are checked with --dump-ast rather than --check: they
 exercise the grammar, and several are deliberately not well-typed.
 
-This runs on the host in about a second. There is no VM: nothing here executes
-generated code, because there is no code generator.
+This runs on the host in about a second. It checks what the compiler says; what
+the compiled programs actually do is `exec.py`.
 """
 from __future__ import annotations
 
@@ -35,8 +34,6 @@ FIXTURES = ROOT / "fec" / "tests"
 WATCOM = ROOT / ".dosboxx" / "watcom"
 SOURCES = ("arena", "diag", "lexer", "ast", "parser", "types", "m7", "own",
            "check", "resolve", "ir", "lower", "x86", "driver")
-# Fixtures live here until there is a code generator to run them against.
-QUARANTINE = "pending-backend"
 
 MARKER = re.compile(r"^//\s*ERROR:(?:(\d+):)?(.*)$")
 
@@ -116,7 +113,7 @@ def main() -> int:
     args = ap.parse_args()
 
     fec = build(ROOT / ".build")
-    cases = sorted(p for p in FIXTURES.rglob("*.fe") if QUARANTINE not in p.parts)
+    cases = sorted(FIXTURES.rglob("*.fe"))
     if args.select:
         cases = [p for p in cases if args.select in p.as_posix()]