diff --git a/src/lib.rs b/src/lib.rs
index df3ba9e..dfbab4f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,7 @@ use clap::{Args, Parser, Subcommand};
 
 mod bindings;
 mod cli;
-mod make_nar;
+pub mod make_nar;
 pub mod path_info;
 pub mod push;
 pub mod store;
diff --git a/src/make_nar.rs b/src/make_nar.rs
index b5c1ab2..97d6b1f 100644
--- a/src/make_nar.rs
+++ b/src/make_nar.rs
@@ -15,10 +15,10 @@ use crate::store::Store;
 pub struct MakeNar<'a> {
     path_info: &'a PathInfo,
     store: Arc<Store>,
-    nar_hasher: Sha256,
+    pub nar_hasher: Sha256,
     /// hash of compressed nar file
     file_hasher: Sha256,
-    nar_size: u64,
+    pub nar_size: u64,
     file_size: u64,
 }
 
diff --git a/tests/common/mod.rs b/tests/common/mod.rs
index 96ba300..aed468f 100644
--- a/tests/common/mod.rs
+++ b/tests/common/mod.rs
@@ -1,12 +1,20 @@
+#![allow(dead_code)]
+
+use std::sync::Arc;
+
 use nixcp::store::Store;
 
+pub const HELLO: &str = "github:nixos/nixpkgs?ref=f771eb401a46846c1aebd20552521b233dd7e18b#hello";
+pub const HELLO_DRV: &str = "iqbwkm8mjjjlmw6x6ry9rhzin2cp9372-hello-2.12.1.drv";
+pub const HELLO_PATH: &str = "/nix/store/9bwryidal9q3g91cjm6xschfn4ikd82q-hello-2.12.1";
+
 pub struct Context {
-    pub store: Store,
+    pub store: Arc<Store>,
 }
 
 impl Context {
     fn new() -> Self {
-        let store = Store::connect().expect("connect to nix store");
+        let store = Arc::new(Store::connect().expect("connect to nix store"));
         Self { store }
     }
 }
diff --git a/tests/nar.rs b/tests/nar.rs
new file mode 100644
index 0000000..5ebadc5
--- /dev/null
+++ b/tests/nar.rs
@@ -0,0 +1,26 @@
+use crate::common::HELLO_PATH;
+use nix_compat::nixbase32;
+use nixcp::make_nar::MakeNar;
+use nixcp::path_info::PathInfo;
+use sha2::Digest;
+use tokio::io::AsyncReadExt;
+
+mod common;
+
+#[tokio::test]
+async fn nar_size_and_hash() {
+    let ctx = common::context();
+    let path_info = PathInfo::from_path(HELLO_PATH, &ctx.store).await.unwrap();
+
+    let mut nar = MakeNar::new(&path_info, ctx.store).unwrap();
+    let mut reader = nar.compress_and_hash().unwrap();
+    let mut buf = Vec::new();
+    reader.read_to_end(&mut buf).await.unwrap();
+    drop(reader);
+
+    assert_eq!(nar.nar_size, 234680);
+
+    let nar_hash = nar.nar_hasher.finalize();
+    let real_nar_hash = "08za7nnjda8kpdsd73v3mhykjvp0rsmskwsr37winhmzgm6iw79w";
+    assert_eq!(nixbase32::encode(nar_hash.as_slice()), real_nar_hash);
+}
diff --git a/tests/path_info.rs b/tests/path_info.rs
index 59b3dfd..2d698d0 100644
--- a/tests/path_info.rs
+++ b/tests/path_info.rs
@@ -2,10 +2,9 @@ use nixcp::path_info::PathInfo;
 use std::path::PathBuf;
 use std::process::Command;
 
-mod common;
+use crate::common::{HELLO, HELLO_DRV, HELLO_PATH};
 
-const HELLO: &str = "github:nixos/nixpkgs?ref=f771eb401a46846c1aebd20552521b233dd7e18b#hello";
-const HELLO_DRV: &str = "iqbwkm8mjjjlmw6x6ry9rhzin2cp9372-hello-2.12.1.drv";
+mod common;
 
 #[tokio::test]
 async fn path_info_from_package() {
@@ -27,7 +26,7 @@ async fn path_info_from_path() {
         .status()
         .unwrap();
     let ctx = common::context();
-    let path = PathBuf::from("/nix/store/9bwryidal9q3g91cjm6xschfn4ikd82q-hello-2.12.1");
+    let path = PathBuf::from(HELLO_PATH);
     let path_info = PathInfo::from_derivation(&path, &ctx.store)
         .await
         .expect("get pathinfo from package");