add path_info tests

tests/common/mod.rs

@@ -0,0 +1,16 @@
+use nixcp::store::Store;
+
+pub struct Context {
+    pub store: Store,
+}
+
+impl Context {
+    fn new() -> Self {
+        let store = Store::connect().expect("connect to nix store");
+        Self { store }
+    }
+}
+
+pub fn context() -> Context {
+    Context::new()
+}