diff --git a/tests/lean/run/def12.lean b/tests/lean/run/def12.lean
new file mode 100644
index 0000000000..f0eca4c585
--- /dev/null
+++ b/tests/lean/run/def12.lean
@@ -0,0 +1,45 @@
+set_option new_elaborator true
+open nat
+
+theorem bit0_succ_eq (n : ℕ) : bit0 (succ n) = succ (succ (bit0 n)) :=
+show succ (succ n + n) = succ (succ (n + n)), from
+succ_add n n ▸ rfl
+
+theorem bit1_eq_succ_bit0 (n : ℕ) : bit1 n = succ (bit0 n) :=
+rfl
+
+theorem bit1_succ_eq (n : ℕ) : bit1 (succ n) = succ (succ (bit1 n)) :=
+eq.trans (nat.bit1_eq_succ_bit0 (succ n)) (congr_arg succ (nat.bit0_succ_eq n))
+
+theorem succ_ne_zero (n : ℕ) : succ n ≠ 0 :=
+assume h, nat.no_confusion h
+
+theorem succ_ne_self : ∀ (n : ℕ), succ n ≠ n
+| 0     h := absurd h (nat.succ_ne_zero 0)
+| (n+1) h := succ_ne_self n (nat.no_confusion h (λ h, h))
+
+theorem bit0_ne_zero : ∀ (n : ℕ), n ≠ 0 → bit0 n ≠ 0
+| 0     h := absurd rfl h
+| (n+1) h := nat.succ_ne_zero _
+
+theorem bit1_ne_one : ∀ (n : ℕ), n ≠ 0 → bit1 n ≠ 1
+| 0     h h1 := absurd rfl h
+| (n+1) h h1 := nat.no_confusion h1 (λ h2, absurd h2 (nat.succ_ne_zero _))
+
+theorem add_self_ne_one : ∀ (n : ℕ), n + n ≠ 1
+| 0     h := nat.no_confusion h
+| (n+1) h :=
+  have h1 : succ (succ (n + n)) = 1, from succ_add n n ▸ h,
+  nat.no_confusion h1 (λ h2, absurd h2 (nat.succ_ne_zero (n + n)))
+
+theorem bit1_ne_bit0 : ∀ (n m : ℕ), bit1 n ≠ bit0 m
+| 0     m     h := absurd h (ne.symm (nat.add_self_ne_one m))
+| (n+1) 0     h :=
+  have h1 : succ (bit0 (succ n)) = 0, from h,
+  absurd h1 (nat.succ_ne_zero _)
+| (n+1) (m+1) h :=
+  have h1 : succ (succ (bit1 n)) = succ (succ (bit0 m)), from
+    nat.bit0_succ_eq m ▸ nat.bit1_succ_eq n ▸ h,
+  have h2 : bit1 n = bit0 m, from
+    nat.no_confusion h1 (λ h2', nat.no_confusion h2' (λ h2'', h2'')),
+  absurd h2 (bit1_ne_bit0 n m)