diff --git a/tests/multipart.rs b/tests/multipart.rs
new file mode 100644
index 0000000..7374858
--- /dev/null
+++ b/tests/multipart.rs
@@ -0,0 +1,80 @@
+use s3_server::dto::{
+    ByteStream, CompleteMultipartUploadRequest, CompletedMultipartUpload, CompletedPart,
+    CreateBucketRequest, CreateMultipartUploadRequest, UploadPartRequest,
+};
+use s3_server::storages::fs::FileSystem;
+use s3_server::S3Storage;
+
+use std::path::PathBuf;
+
+use uuid::Uuid;
+
+fn setup_fs() -> (PathBuf, FileSystem) {
+    let root = std::env::temp_dir().join(format!("s3-server-test-{}", Uuid::new_v4()));
+    std::fs::create_dir_all(&root).unwrap();
+    let fs = FileSystem::new(&root).unwrap();
+    (root, fs)
+}
+
+#[tokio::test]
+async fn complete_multipart_upload_creates_parent_dirs() {
+    let (root, fs) = setup_fs();
+
+    let bucket = "test-bucket";
+    // A prefixed key whose parent dirs do not exist yet; CompleteMultipartUpload
+    // must create them instead of failing File::create with NotFound.
+    let key = "simple/pkg/x.whl";
+
+    fs.create_bucket(CreateBucketRequest {
+        bucket: bucket.to_owned(),
+        ..Default::default()
+    })
+    .await
+    .unwrap();
+
+    let upload = fs
+        .create_multipart_upload(CreateMultipartUploadRequest {
+            bucket: bucket.to_owned(),
+            key: key.to_owned(),
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+    let upload_id = upload.upload_id.unwrap();
+
+    let content = b"hello multipart".to_vec();
+    let part = fs
+        .upload_part(UploadPartRequest {
+            bucket: bucket.to_owned(),
+            key: key.to_owned(),
+            upload_id: upload_id.clone(),
+            part_number: 1,
+            body: Some(ByteStream::from(content.clone())),
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    let output = fs
+        .complete_multipart_upload(CompleteMultipartUploadRequest {
+            bucket: bucket.to_owned(),
+            key: key.to_owned(),
+            upload_id,
+            multipart_upload: Some(CompletedMultipartUpload {
+                parts: Some(vec![CompletedPart {
+                    e_tag: part.e_tag,
+                    part_number: Some(1),
+                }]),
+            }),
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    assert!(output.e_tag.is_some());
+
+    let written = std::fs::read(root.join(bucket).join(key)).unwrap();
+    assert_eq!(written, content);
+
+    std::fs::remove_dir_all(&root).ok();
+}