tests use mockall for expectation-style doubles, starting with the builder and hive-priv seams

hive-priv/Cargo.toml

@@ -16,3 +16,6 @@ serde_json.workspace = true
 tokio.workspace = true
 tracing.workspace = true
 tracing-subscriber.workspace = true
+
+[dev-dependencies]
+mockall.workspace = true

hive-priv/src/storage.rs

@@ -179,6 +179,7 @@ fn is_subvolume_root(on_btrfs: bool, ino: Option<u64>) -> bool {
 
 /// The two questions the storage ops ask the state filesystem. [`RealProbes`]
 /// is production; tests answer without a btrfs filesystem.
+#[cfg_attr(test, mockall::automock)]
 trait Probes {
     /// Whether `path` lives on a btrfs filesystem; an error when it cannot be
     /// told.
@@ -1009,7 +1010,7 @@ async fn set_subvolume_quota(
 #[cfg(test)]
 mod tests {
     use super::{
-        Command, Env, Probes, agent_disk_paths, cleanup_stale_path, delete_agent_snapshot,
+        Command, Env, MockProbes, agent_disk_paths, cleanup_stale_path, delete_agent_snapshot,
         delete_agent_subvolume, du_command, du_total, ensure_agent_subvolume,
         ensure_btrfs_quota_in, exec_delete_agent_snapshot, exec_delete_agent_subvolume,
         exec_ensure_agent_subvolume, exec_measure_agent_disk, exec_read_subvolume_usage,
@@ -1412,21 +1413,31 @@ mod tests {
                 .collect()
         }
 
-        /// An [`Env`] over this tree, running `btrfs` and the two probes given.
+        /// An [`Env`] over this tree, running `btrfs` and probes that answer
+        /// with the functions given.
         fn env<'a, S: Spawn>(
             &'a self,
             spawn: &'a S,
             on_btrfs: fn(&Path) -> anyhow::Result<bool>,
             is_subvolume: fn(&Path) -> bool,
-        ) -> Env<'a, &'a S, FnProbes> {
+        ) -> Env<'a, &'a S, MockProbes> {
+            let mut probes = MockProbes::new();
+            probes.expect_on_btrfs().returning(on_btrfs);
+            probes.expect_is_subvolume().returning(is_subvolume);
+            self.env_with(spawn, probes)
+        }
+
+        /// An [`Env`] over this tree, running `btrfs` and the `probes` given.
+        fn env_with<'a, S: Spawn>(
+            &'a self,
+            spawn: &'a S,
+            probes: MockProbes,
+        ) -> Env<'a, &'a S, MockProbes> {
             Env {
                 state_root: &self.state,
                 staging_root: &self.staging,
                 spawn,
-                probes: FnProbes {
-                    on_btrfs,
-                    is_subvolume,
-                },
+                probes,
             }
         }
 
@@ -1440,22 +1451,6 @@ mod tests {
         }
     }
 
-    /// Probes answered by the functions given.
-    struct FnProbes {
-        on_btrfs: fn(&Path) -> anyhow::Result<bool>,
-        is_subvolume: fn(&Path) -> bool,
-    }
-
-    impl Probes for FnProbes {
-        fn on_btrfs(&self, path: &Path) -> anyhow::Result<bool> {
-            (self.on_btrfs)(path)
-        }
-
-        fn is_subvolume(&self, path: &Path) -> bool {
-            (self.is_subvolume)(path)
-        }
-    }
-
     /// Creates, deletes and snapshots as btrfs does; `send` writes `STREAM`.
     const LIKE_BTRFS: &str = r#"case "$1 $2" in
   "subvolume create") mkdir "$3";;
@@ -1490,7 +1485,8 @@ esac"#;
         let fx = Fx::new();
         std::fs::create_dir(fx.agent("iris")).unwrap();
         let btrfs = fx.btrfs(LIKE_BTRFS);
-        let env = fx.env(&btrfs, on_btrfs, not_subvol);
+        // No expectation is set: a probe call would panic.
+        let env = fx.env_with(&btrfs, MockProbes::new());
         assert_eq!(
             ensure_agent_subvolume(&env, "iris").await.unwrap(),
             (String::new(), String::new())