move "nix build" to tests/common

tests/common/mod.rs

@@ -1,5 +1,6 @@
 #![allow(dead_code)]
 
+use std::process::Command;
 use std::sync::Arc;
 
 use nixcp::store::Store;
@@ -14,6 +15,13 @@ pub struct Context {
 
 impl Context {
     fn new() -> Self {
+        // hello must be in the store
+        Command::new("nix")
+            .arg("build")
+            .arg("--no-link")
+            .arg(HELLO)
+            .status()
+            .unwrap();
         let store = Arc::new(Store::connect().expect("connect to nix store"));
         Self { store }
     }

tests/path_info.rs

@@ -1,6 +1,5 @@
 use nixcp::path_info::PathInfo;
 use std::path::PathBuf;
-use std::process::Command;
 
 use crate::common::{HELLO, HELLO_DRV, HELLO_PATH};
 
@@ -18,13 +17,6 @@ async fn path_info_from_package() {
 
 #[tokio::test]
 async fn path_info_from_path() {
-    // the path must be in the store
-    Command::new("nix")
-        .arg("build")
-        .arg("--no-link")
-        .arg(HELLO)
-        .status()
-        .unwrap();
     let ctx = common::context();
     let path = PathBuf::from(HELLO_PATH);
     let path_info = PathInfo::from_derivation(&path, &ctx.store)