refactor(tvix/castore): move src/fs/test into fuse mod r/8172

These tests only interact with the FUSE layer, and
import super::fuse to do its work.

However, this only works if the `fuse` feature is enabled, which we
don't do if we enable the `virtiofs` feature only, causing the tests
to fail:

```
❯ cargo test --no-default-features --features virtiofs
   Compiling tvix-castore v0.1.0 (/home/flokli/dev/nixos/code.tvl.fyi-submit2/tvix/castore)
error[E0432]: unresolved import `super::fuse`
  --> castore/src/fs/tests.rs:14:13
   |
14 | use super::{fuse::FuseDaemon, TvixStoreFs};
   |             ^^^^ could not find `fuse` in `super`
```

We move src/fs/tests.rs to src/fs/fuse/tests.rs
(and src/fs/fuse.rs to src/fs/fuse/mod.rs) to better structure this,
which will automatically cause both tests and code to only be built if
we have the `fuse` feature enabled.

Change-Id: I8fbbad3e4457e326bdfd171aa5c43d25d3187b5b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11715
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

3 files changed, 9 insertions, 8 deletions

diff --git a/tvix/castore/src/fs/fuse.rs b/tvix/castore/src/fs/fuse/mod.rs
index cd50618ff5..94b73d422a 100644
--- a/tvix/castore/src/fs/fuse.rs
+++ b/tvix/castore/src/fs/fuse/mod.rs
@@ -3,6 +3,9 @@ use std::{io, path::Path, sync::Arc, thread};
 use fuse_backend_rs::{api::filesystem::FileSystem, transport::FuseSession};
 use tracing::{error, instrument};
 
+#[cfg(test)]
+mod tests;
+
 struct FuseServer<FS>
 where
     FS: FileSystem + Sync + Send,
diff --git a/tvix/castore/src/fs/tests.rs b/tvix/castore/src/fs/fuse/tests.rs
index d6eeb8a411..bb321f5888 100644
--- a/tvix/castore/src/fs/tests.rs
+++ b/tvix/castore/src/fs/fuse/tests.rs
@@ -11,7 +11,8 @@ use std::{
 use tempfile::TempDir;
 use tokio_stream::{wrappers::ReadDirStream, StreamExt};
 
-use super::{fuse::FuseDaemon, TvixStoreFs};
+use super::FuseDaemon;
+use crate::fs::{TvixStoreFs, XATTR_NAME_BLOB_DIGEST, XATTR_NAME_DIRECTORY_DIGEST};
 use crate::proto as castorepb;
 use crate::proto::node::Node;
 use crate::{
@@ -614,12 +615,12 @@ async fn xattr() {
         // There should be 1 key, XATTR_NAME_DIRECTORY_DIGEST.
         assert_eq!(1, xattr_names.len(), "there should be 1 xattr name");
         assert_eq!(
-            super::XATTR_NAME_DIRECTORY_DIGEST,
+            XATTR_NAME_DIRECTORY_DIGEST,
             xattr_names.first().unwrap().as_encoded_bytes()
         );
 
         // The key should equal to the string-formatted b3 digest.
-        let val = xattr::get(&p, OsStr::from_bytes(super::XATTR_NAME_DIRECTORY_DIGEST))
+        let val = xattr::get(&p, OsStr::from_bytes(XATTR_NAME_DIRECTORY_DIGEST))
             .expect("must succeed")
             .expect("must be some");
         assert_eq!(
@@ -643,12 +644,12 @@ async fn xattr() {
         // There should be 1 key, XATTR_NAME_BLOB_DIGEST.
         assert_eq!(1, xattr_names.len(), "there should be 1 xattr name");
         assert_eq!(
-            super::XATTR_NAME_BLOB_DIGEST,
+            XATTR_NAME_BLOB_DIGEST,
             xattr_names.first().unwrap().as_encoded_bytes()
         );
 
         // The key should equal to the string-formatted b3 digest.
-        let val = xattr::get(&p, OsStr::from_bytes(super::XATTR_NAME_BLOB_DIGEST))
+        let val = xattr::get(&p, OsStr::from_bytes(XATTR_NAME_BLOB_DIGEST))
             .expect("must succeed")
             .expect("must be some");
         assert_eq!(
diff --git a/tvix/castore/src/fs/mod.rs b/tvix/castore/src/fs/mod.rs
index 826523131f..176199f64a 100644
--- a/tvix/castore/src/fs/mod.rs
+++ b/tvix/castore/src/fs/mod.rs
@@ -9,9 +9,6 @@ pub mod fuse;
 #[cfg(feature = "virtiofs")]
 pub mod virtiofs;
 
-#[cfg(test)]
-mod tests;
-
 pub use self::root_nodes::RootNodes;
 use self::{
     file_attr::ROOT_FILE_ATTR,