diff --git a/.changeset/tricky-llamas-collect.md b/.changeset/tricky-llamas-collect.md
new file mode 100644
index 000000000000..0b8d3debe449
--- /dev/null
+++ b/.changeset/tricky-llamas-collect.md
@@ -0,0 +1,6 @@
+---
+swc_core: patch
+swc_ecma_transforms_testing: patch
+---
+
+fix(es/testing): Fix sourcemap generation
diff --git a/Cargo.lock b/Cargo.lock
index 3245ca079ce9..7a7cb03f4287 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -5610,6 +5610,7 @@ dependencies = [
  "serde_json",
  "sha2",
  "sourcemap",
+ "swc_allocator",
  "swc_common",
  "swc_ecma_ast",
  "swc_ecma_codegen",
diff --git a/crates/swc_ecma_transforms_testing/Cargo.toml b/crates/swc_ecma_transforms_testing/Cargo.toml
index b9129c78f3ef..dc9414ade97b 100644
--- a/crates/swc_ecma_transforms_testing/Cargo.toml
+++ b/crates/swc_ecma_transforms_testing/Cargo.toml
@@ -22,6 +22,7 @@ sha2       = { workspace = true }
 sourcemap  = { workspace = true }
 tempfile   = { workspace = true }
 
+swc_allocator = { version = "2.0.0", path = "../swc_allocator", default-features = false }
 swc_common = { version = "5.0.0", path = "../swc_common", features = [
   "sourcemap",
 ] }
diff --git a/crates/swc_ecma_transforms_testing/src/lib.rs b/crates/swc_ecma_transforms_testing/src/lib.rs
index 38bb0231e1a1..834096383e7a 100644
--- a/crates/swc_ecma_transforms_testing/src/lib.rs
+++ b/crates/swc_ecma_transforms_testing/src/lib.rs
@@ -27,7 +27,7 @@ use swc_common::{
     FileName, Mark, SourceMap, DUMMY_SP,
 };
 use swc_ecma_ast::*;
-use swc_ecma_codegen::to_code_default;
+use swc_ecma_codegen::{to_code_default, Emitter};
 use swc_ecma_parser::{lexer::Lexer, Parser, StringInput, Syntax};
 use swc_ecma_testing::{exec_node_js, JsExecOptions};
 use swc_ecma_transforms_base::{
@@ -900,7 +900,7 @@ fn test_fixture_inner<'a>(
     });
 
     let mut src_map = if config.sourcemap {
-        Some(Vec::new())
+        Some(swc_allocator::maybe::vec::Vec::new())
     } else {
         None
     };
@@ -942,6 +942,24 @@ fn test_fixture_inner<'a>(
             let module = &actual;
             let comments: &Rc<SingleThreadedComments> = &tester.comments.clone();
 
+            let mut buf = vec![];
+            {
+                let mut emitter = Emitter {
+                    cfg: Default::default(),
+                    cm: tester.cm.clone(),
+                    wr: Box::new(swc_ecma_codegen::text_writer::JsWriter::new(
+                        tester.cm.clone(),
+                        "\n",
+                        &mut buf,
+                        src_map.as_mut(),
+                    )),
+                    comments: Some(comments),
+                };
+
+                // println!("Emitting: {:?}", module);
+                emitter.emit_program(module).unwrap();
+            }
+
             if let Some(src_map) = &mut src_map {
                 sourcemap = Some(tester.cm.build_source_map_with_config(
                     src_map,
@@ -950,7 +968,7 @@ fn test_fixture_inner<'a>(
                 ));
             }
 
-            to_code_default(tester.cm.clone(), Some(comments), module)
+            String::from_utf8(buf).expect("codegen generated non-utf8 output")
         };
 
         Ok(actual_src)