diff --git a/crates/oxide_cfg/src/lib.rs b/crates/oxide_cfg/src/lib.rs
index 38bb1efd..a9375c5b 100644
--- a/crates/oxide_cfg/src/lib.rs
+++ b/crates/oxide_cfg/src/lib.rs
@@ -98,174 +98,3 @@ pub fn build_cfg(f: &IRFunction) -> Cfg {
     cfg_debug!("build_cfg: {} blocks", cfg.blocks.len());
     cfg
 }
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use oxide_ir::inst::Inst;
-    use oxide_ir::operand::Operand;
-
-    fn succs_total(cfg: &Cfg) -> usize {
-        cfg.blocks.iter().map(|b| b.succs.len()).sum()
-    }
-
-    fn preds_total(cfg: &Cfg) -> usize {
-        cfg.blocks.iter().map(|b| b.preds.len()).sum()
-    }
-
-    /// 无跳转线性函数：1 实块 + exit 哨兵，块 0 Fallthrough→exit，preds/succs 对称。
-    #[test]
-    fn linear_function_is_single_block_plus_exit() {
-        let mut f = IRFunction::new();
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None));
-
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 2); // 1 实块 + exit 哨兵
-        assert_eq!(cfg.entry, 0);
-        assert_eq!(cfg.exit, 1);
-        assert_eq!(cfg.blocks[0].inst_range, 0..3);
-        assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
-        assert!(cfg.blocks[1].succs.is_empty()); // exit 哨兵无出边
-        assert_eq!(cfg.blocks[1].preds, vec![0]);
-        assert_eq!(succs_total(&cfg), preds_total(&cfg));
-    }
-
-    /// if/else 典型形状：条件分裂块（Jump + Fallthrough 双出边），4 实块 + exit 哨兵。
-    #[test]
-    fn if_else_conditional_jump_splits_block_with_dual_edges() {
-        let mut f = IRFunction::new();
-        f.insts.push(Inst::jmp_if_false(1, 0)); // 0: cond → L0(else)
-        f.insts.push(Inst::call(Operand::Reg(2), Operand::Reg(0), Operand::Reg(3), 1)); // 1: then a()
-        f.insts.push(Inst::jmp(1)); // 2: → L1(end)
-        f.insts.push(Inst::call(Operand::Reg(4), Operand::Reg(0), Operand::Reg(3), 1)); // 3: else b()
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
-        f.label_pos = vec![Some(3), Some(4)]; // L0→else 块头(3), L1→end(4)
-        f.label_count = 2;
-
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 5); // 4 实块 + exit 哨兵
-        assert_eq!(cfg.entry, 0);
-        assert_eq!(cfg.exit, 4);
-
-        // 块 0（cond）：条件分裂，Jump→else + Fallthrough→then 两条出边都在
-        assert_eq!(cfg.blocks[0].inst_range, 0..1);
-        assert_eq!(cfg.blocks[0].succs, vec![(2, EdgeKind::Jump), (1, EdgeKind::Fallthrough)]);
-        assert!(cfg.blocks[0].preds.is_empty());
-        // 块 1（then）：Jump→end
-        assert_eq!(cfg.blocks[1].inst_range, 1..3);
-        assert_eq!(cfg.blocks[1].succs, vec![(3, EdgeKind::Jump)]);
-        assert_eq!(cfg.blocks[1].preds, vec![0]);
-        // 块 2（else）：Fallthrough→end
-        assert_eq!(cfg.blocks[2].inst_range, 3..4);
-        assert_eq!(cfg.blocks[2].succs, vec![(3, EdgeKind::Fallthrough)]);
-        assert_eq!(cfg.blocks[2].preds, vec![0]);
-        // 块 3（end）：RETURN → Fallthrough→exit
-        assert_eq!(cfg.blocks[3].inst_range, 4..5);
-        assert_eq!(cfg.blocks[3].succs, vec![(4, EdgeKind::Fallthrough)]);
-        assert_eq!(cfg.blocks[3].preds, vec![1, 2]);
-        // 块 4（exit 哨兵）：空块 0..0，preds 含块 3，无出边
-        assert_eq!(cfg.blocks[4].inst_range, 0..0);
-        assert!(cfg.blocks[4].succs.is_empty());
-        assert_eq!(cfg.blocks[4].preds, vec![3]);
-        assert_eq!(succs_total(&cfg), preds_total(&cfg));
-    }
-
-    /// try/catch：TRY_BEGIN 是块内标记不切块，所在 BB 出 Exception 边到 catch 入口。
-    #[test]
-    fn try_begin_does_not_split_block_and_emits_exception_edge() {
-        let mut f = IRFunction::new();
-        f.insts.push(Inst::try_begin(0)); // 0: TRY_BEGIN（块内标记）
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: catch 入口
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
-        f.label_pos = vec![Some(3)];
-        f.label_count = 1;
-
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 3); // 2 实块 + exit 哨兵（TRY_BEGIN 不切块）
-        assert_eq!(cfg.blocks[0].inst_range, 0..3); // try 体未被切块
-                                                    // Exception 边从 TRY_BEGIN 所在 BB 出发指向 catch 入口块。
-        assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
-        assert_eq!(cfg.blocks[1].succs, vec![(2, EdgeKind::Fallthrough)]);
-        assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
-        assert_eq!(succs_total(&cfg), preds_total(&cfg));
-    }
-
-    /// try/finally：TRY_FINALLY_BEGIN 同上，Exception 边到 finally 入口块。
-    #[test]
-    fn try_finally_begin_emits_exception_edge() {
-        let mut f = IRFunction::new();
-        f.insts.push(Inst::try_finally_begin(0)); // 0
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: finally 入口
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
-        f.label_pos = vec![Some(3)];
-        f.label_count = 1;
-
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 3);
-        assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
-        assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
-        assert_eq!(succs_total(&cfg), preds_total(&cfg));
-    }
-
-    /// 尾部 RETURN：该块 Fallthrough 到 exit。
-    #[test]
-    fn trailing_return_flows_to_exit() {
-        let mut f = IRFunction::new();
-        f.insts
-            .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None));
-
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 2);
-        assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
-        assert_eq!(cfg.blocks[1].preds, vec![0]);
-    }
-
-    /// 空 IRFunction：退化 CFG，entry == exit == 0，blocks 长度 1。
-    #[test]
-    fn empty_function_yields_degenerate_cfg() {
-        let f = IRFunction::new();
-        let cfg = build_cfg(&f);
-        assert_eq!(cfg.blocks.len(), 1);
-        assert_eq!(cfg.entry, 0);
-        assert_eq!(cfg.exit, 0);
-        assert_eq!(cfg.blocks[0].inst_range, 0..0);
-        assert!(cfg.blocks[0].succs.is_empty());
-        assert!(cfg.blocks[0].preds.is_empty());
-    }
-
-    /// 幂等性：同一 IR 两次构建结果相等。
-    #[test]
-    fn build_cfg_is_idempotent() {
-        let mut f = IRFunction::new();
-        f.insts.push(Inst::jmp_if_false(1, 0)); // 0: → L0（回环目标）
-        f.insts.push(Inst::jmp(0)); // 1: → L0
-        f.insts
-            .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
-        f.label_pos = vec![Some(2), Some(0)]; // L0→2（尾部）, L1→0（回环）
-        f.label_count = 2;
-
-        let cfg1 = build_cfg(&f);
-        let cfg2 = build_cfg(&f);
-        assert_eq!(cfg1, cfg2);
-    }
-}
diff --git a/crates/oxide_cfg/tests/build_unit.rs b/crates/oxide_cfg/tests/build_unit.rs
new file mode 100644
index 00000000..4987fc3b
--- /dev/null
+++ b/crates/oxide_cfg/tests/build_unit.rs
@@ -0,0 +1,173 @@
+//! build_cfg 结构形状单测：IRFunction → Cfg。
+//!
+//! 覆盖块划分、条件双出边、try 异常边、exit 哨兵、退化形态与幂等；只走 pub API。
+
+use oxide_bytecode::opcode::OpCode;
+use oxide_cfg::{build_cfg, Cfg, EdgeKind};
+use oxide_ir::inst::Inst;
+use oxide_ir::operand::Operand;
+use oxide_ir::IRFunction;
+
+fn succs_total(cfg: &Cfg) -> usize {
+    cfg.blocks.iter().map(|b| b.succs.len()).sum()
+}
+
+fn preds_total(cfg: &Cfg) -> usize {
+    cfg.blocks.iter().map(|b| b.preds.len()).sum()
+}
+
+/// 无跳转线性函数：1 实块 + exit 哨兵，块 0 Fallthrough→exit，preds/succs 对称。
+#[test]
+fn linear_function_is_single_block_plus_exit() {
+    let mut f = IRFunction::new();
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None));
+
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 2); // 1 实块 + exit 哨兵
+    assert_eq!(cfg.entry, 0);
+    assert_eq!(cfg.exit, 1);
+    assert_eq!(cfg.blocks[0].inst_range, 0..3);
+    assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
+    assert!(cfg.blocks[1].succs.is_empty()); // exit 哨兵无出边
+    assert_eq!(cfg.blocks[1].preds, vec![0]);
+    assert_eq!(succs_total(&cfg), preds_total(&cfg));
+}
+
+/// if/else 典型形状：条件分裂块（Jump + Fallthrough 双出边），4 实块 + exit 哨兵。
+#[test]
+fn if_else_conditional_jump_splits_block_with_dual_edges() {
+    let mut f = IRFunction::new();
+    f.insts.push(Inst::jmp_if_false(1, 0)); // 0: cond → L0(else)
+    f.insts.push(Inst::call(Operand::Reg(2), Operand::Reg(0), Operand::Reg(3), 1)); // 1: then a()
+    f.insts.push(Inst::jmp(1)); // 2: → L1(end)
+    f.insts.push(Inst::call(Operand::Reg(4), Operand::Reg(0), Operand::Reg(3), 1)); // 3: else b()
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
+    f.label_pos = vec![Some(3), Some(4)]; // L0→else 块头(3), L1→end(4)
+    f.label_count = 2;
+
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 5); // 4 实块 + exit 哨兵
+    assert_eq!(cfg.entry, 0);
+    assert_eq!(cfg.exit, 4);
+
+    // 块 0（cond）：条件分裂，Jump→else + Fallthrough→then 两条出边都在
+    assert_eq!(cfg.blocks[0].inst_range, 0..1);
+    assert_eq!(cfg.blocks[0].succs, vec![(2, EdgeKind::Jump), (1, EdgeKind::Fallthrough)]);
+    assert!(cfg.blocks[0].preds.is_empty());
+    // 块 1（then）：Jump→end
+    assert_eq!(cfg.blocks[1].inst_range, 1..3);
+    assert_eq!(cfg.blocks[1].succs, vec![(3, EdgeKind::Jump)]);
+    assert_eq!(cfg.blocks[1].preds, vec![0]);
+    // 块 2（else）：Fallthrough→end
+    assert_eq!(cfg.blocks[2].inst_range, 3..4);
+    assert_eq!(cfg.blocks[2].succs, vec![(3, EdgeKind::Fallthrough)]);
+    assert_eq!(cfg.blocks[2].preds, vec![0]);
+    // 块 3（end）：RETURN → Fallthrough→exit
+    assert_eq!(cfg.blocks[3].inst_range, 4..5);
+    assert_eq!(cfg.blocks[3].succs, vec![(4, EdgeKind::Fallthrough)]);
+    assert_eq!(cfg.blocks[3].preds, vec![1, 2]);
+    // 块 4（exit 哨兵）：空块 0..0，preds 含块 3，无出边
+    assert_eq!(cfg.blocks[4].inst_range, 0..0);
+    assert!(cfg.blocks[4].succs.is_empty());
+    assert_eq!(cfg.blocks[4].preds, vec![3]);
+    assert_eq!(succs_total(&cfg), preds_total(&cfg));
+}
+
+/// try/catch：TRY_BEGIN 是块内标记不切块，所在 BB 出 Exception 边到 catch 入口。
+#[test]
+fn try_begin_does_not_split_block_and_emits_exception_edge() {
+    let mut f = IRFunction::new();
+    f.insts.push(Inst::try_begin(0)); // 0: TRY_BEGIN（块内标记）
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: catch 入口
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
+    f.label_pos = vec![Some(3)];
+    f.label_count = 1;
+
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 3); // 2 实块 + exit 哨兵（TRY_BEGIN 不切块）
+    assert_eq!(cfg.blocks[0].inst_range, 0..3); // try 体未被切块
+                                                // Exception 边从 TRY_BEGIN 所在 BB 出发指向 catch 入口块。
+    assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
+    assert_eq!(cfg.blocks[1].succs, vec![(2, EdgeKind::Fallthrough)]);
+    assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
+    assert_eq!(succs_total(&cfg), preds_total(&cfg));
+}
+
+/// try/finally：TRY_FINALLY_BEGIN 同上，Exception 边到 finally 入口块。
+#[test]
+fn try_finally_begin_emits_exception_edge() {
+    let mut f = IRFunction::new();
+    f.insts.push(Inst::try_finally_begin(0)); // 0
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 1
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None)); // 3: finally 入口
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 4
+    f.label_pos = vec![Some(3)];
+    f.label_count = 1;
+
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 3);
+    assert!(cfg.blocks[0].succs.contains(&(1, EdgeKind::Exception)));
+    assert_eq!(cfg.blocks[2].preds, vec![0, 1]);
+    assert_eq!(succs_total(&cfg), preds_total(&cfg));
+}
+
+/// 尾部 RETURN：该块 Fallthrough 到 exit。
+#[test]
+fn trailing_return_flows_to_exit() {
+    let mut f = IRFunction::new();
+    f.insts
+        .push(Inst::new(OpCode::NOP, Operand::None, Operand::None, Operand::None));
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None));
+
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 2);
+    assert_eq!(cfg.blocks[0].succs, vec![(1, EdgeKind::Fallthrough)]);
+    assert_eq!(cfg.blocks[1].preds, vec![0]);
+}
+
+/// 空 IRFunction：退化 CFG，entry == exit == 0，blocks 长度 1。
+#[test]
+fn empty_function_yields_degenerate_cfg() {
+    let f = IRFunction::new();
+    let cfg = build_cfg(&f);
+    assert_eq!(cfg.blocks.len(), 1);
+    assert_eq!(cfg.entry, 0);
+    assert_eq!(cfg.exit, 0);
+    assert_eq!(cfg.blocks[0].inst_range, 0..0);
+    assert!(cfg.blocks[0].succs.is_empty());
+    assert!(cfg.blocks[0].preds.is_empty());
+}
+
+/// 幂等性：同一 IR 两次构建结果相等。
+#[test]
+fn build_cfg_is_idempotent() {
+    let mut f = IRFunction::new();
+    f.insts.push(Inst::jmp_if_false(1, 0)); // 0: → L0（回环目标）
+    f.insts.push(Inst::jmp(0)); // 1: → L0
+    f.insts
+        .push(Inst::new(OpCode::RETURN, Operand::None, Operand::None, Operand::None)); // 2
+    f.label_pos = vec![Some(2), Some(0)]; // L0→2（尾部）, L1→0（回环）
+    f.label_count = 2;
+
+    let cfg1 = build_cfg(&f);
+    let cfg2 = build_cfg(&f);
+    assert_eq!(cfg1, cfg2);
+}