diff --git a/backends/src/rust/mod.rs b/backends/src/rust/mod.rs
index 13404ad7..900c427d 100644
--- a/backends/src/rust/mod.rs
+++ b/backends/src/rust/mod.rs
@@ -3,7 +3,7 @@ use super::{
     WalkDirResult,
 };
 use anyhow::Result;
-use cargo_metadata::Package;
+use cargo_metadata::{Metadata, Package};
 use necessist_core::{
     framework::{SpanTestMaps, TestSet},
     LightContext, SourceFile, Span, ToInternalSpan, __Rewriter as Rewriter,
@@ -31,6 +31,9 @@ use visitor::{collect_local_functions, visit};
 
 #[derive(Debug)]
 pub struct Rust {
+    source_file_fs_module_path_cache: BTreeMap<PathBuf, Vec<String>>,
+    source_file_package_cache: BTreeMap<PathBuf, Package>,
+    directory_metadata_cache: BTreeMap<PathBuf, Metadata>,
     source_file_flags_cache: BTreeMap<PathBuf, Vec<String>>,
 }
 
@@ -45,6 +48,9 @@ impl Rust {
 
     pub fn new() -> Self {
         Self {
+            source_file_fs_module_path_cache: BTreeMap::new(),
+            source_file_package_cache: BTreeMap::new(),
+            directory_metadata_cache: BTreeMap::new(),
             source_file_flags_cache: BTreeMap::new(),
         }
     }
@@ -59,13 +65,22 @@ pub struct Test<'ast> {
 impl<'ast> Test<'ast> {
     fn new(
         storage: &RefCell<Storage>,
+        source_file_fs_module_path_cache: &mut BTreeMap<PathBuf, Vec<String>>,
+        source_file_package_cache: &mut BTreeMap<PathBuf, Package>,
+        directory_metadata_map: &mut BTreeMap<PathBuf, Metadata>,
         source_file: &SourceFile,
         item_fn: &'ast syn::ItemFn,
     ) -> Option<Self> {
         // smoelius: If the module path cannot be determined, return `None` to prevent the
         // `GenericVisitor` from walking the test.
         let test_name = item_fn.sig.ident.to_string();
-        let result = storage.borrow_mut().test_path(source_file, &test_name);
+        let result = storage.borrow_mut().test_path(
+            source_file_fs_module_path_cache,
+            source_file_package_cache,
+            directory_metadata_map,
+            source_file,
+            &test_name,
+        );
         let test_path = match result {
             Ok(test_path) => test_path,
             Err(error) => {
@@ -658,15 +673,15 @@ impl Rust {
     }
 
     #[cfg_attr(dylint_lib = "general", allow(non_local_effect_before_error_return))]
-    fn cached_source_file_flags(
-        &mut self,
-        source_file_package_map: &mut BTreeMap<PathBuf, Package>,
-        source_file: &Path,
-    ) -> Result<&Vec<String>> {
+    fn cached_source_file_flags(&mut self, source_file: &Path) -> Result<&Vec<String>> {
         self.source_file_flags_cache
             .entry(source_file.to_path_buf())
             .or_try_insert_with(|| {
-                let package = cached_source_file_package(source_file_package_map, source_file)?;
+                let package = cached_source_file_package(
+                    &mut self.source_file_package_cache,
+                    &mut self.directory_metadata_cache,
+                    source_file,
+                )?;
 
                 let mut flags = vec![
                     "--manifest-path".to_owned(),
diff --git a/backends/src/rust/storage.rs b/backends/src/rust/storage.rs
index a4cdc661..76768d2a 100644
--- a/backends/src/rust/storage.rs
+++ b/backends/src/rust/storage.rs
@@ -1,6 +1,6 @@
 use super::TryInsert;
 use anyhow::{anyhow, Error, Result};
-use cargo_metadata::{MetadataCommand, Package};
+use cargo_metadata::{Metadata, MetadataCommand, Package};
 use necessist_core::{util, SourceFile};
 use std::{
     collections::BTreeMap,
@@ -12,8 +12,6 @@ use syn::{File, Ident};
 /// Structures needed during parsing but not after.
 pub struct Storage<'ast> {
     pub module_path: Vec<&'ast Ident>,
-    pub source_file_fs_module_path_cache: BTreeMap<PathBuf, Vec<String>>,
-    pub source_file_package_cache: BTreeMap<PathBuf, Package>,
     pub tests_needing_warnings: BTreeMap<String, Vec<Error>>,
     pub error: Option<Error>,
 }
@@ -22,17 +20,23 @@ impl<'ast> Storage<'ast> {
     pub fn new(_file: &'ast File) -> Self {
         Self {
             module_path: Vec::new(),
-            source_file_fs_module_path_cache: BTreeMap::new(),
-            source_file_package_cache: BTreeMap::new(),
             tests_needing_warnings: BTreeMap::new(),
             error: None,
         }
     }
 
-    pub fn test_path(&mut self, source_file: &SourceFile, name: &str) -> Result<Vec<String>> {
+    pub fn test_path(
+        &mut self,
+        source_file_fs_module_path_map: &mut BTreeMap<PathBuf, Vec<String>>,
+        source_file_package_map: &mut BTreeMap<PathBuf, Package>,
+        directory_metadata_map: &mut BTreeMap<PathBuf, Metadata>,
+        source_file: &SourceFile,
+        name: &str,
+    ) -> Result<Vec<String>> {
         let mut test_path = cached_source_file_fs_module_path(
-            &mut self.source_file_fs_module_path_cache,
-            &mut self.source_file_package_cache,
+            source_file_fs_module_path_map,
+            source_file_package_map,
+            directory_metadata_map,
             source_file,
         )
         .cloned()?;
@@ -46,12 +50,17 @@ impl<'ast> Storage<'ast> {
 pub(super) fn cached_source_file_fs_module_path<'a>(
     source_file_fs_module_path_map: &'a mut BTreeMap<PathBuf, Vec<String>>,
     source_file_package_map: &mut BTreeMap<PathBuf, Package>,
+    directory_metadata_map: &mut BTreeMap<PathBuf, Metadata>,
     source_file: &Path,
 ) -> Result<&'a Vec<String>> {
     source_file_fs_module_path_map
         .entry(source_file.to_path_buf())
         .or_try_insert_with(|| {
-            let package = cached_source_file_package(source_file_package_map, source_file)?;
+            let package = cached_source_file_package(
+                source_file_package_map,
+                directory_metadata_map,
+                source_file,
+            )?;
 
             let manifest_dir = package
                 .manifest_path
@@ -88,6 +97,7 @@ pub(super) fn cached_source_file_fs_module_path<'a>(
 #[cfg_attr(dylint_lib = "general", allow(non_local_effect_before_error_return))]
 pub(super) fn cached_source_file_package<'a>(
     source_file_package_map: &'a mut BTreeMap<PathBuf, Package>,
+    directory_metadata_map: &mut BTreeMap<PathBuf, Metadata>,
     source_file: &Path,
 ) -> Result<&'a Package> {
     source_file_package_map
@@ -97,14 +107,11 @@ pub(super) fn cached_source_file_package<'a>(
                 .parent()
                 .ok_or_else(|| anyhow!("Failed to get parent directory"))?;
 
-            let metadata = MetadataCommand::new()
-                .current_dir(parent)
-                .no_deps()
-                .exec()?;
+            let metadata = cached_directory_metadata(directory_metadata_map, parent)?;
 
             // smoelius: Use the package whose manifest directory is nearest to the source file.
             let mut package_near: Option<Package> = None;
-            for package_curr in metadata.packages {
+            for package_curr in &metadata.packages {
                 let manifest_dir = package_curr
                     .manifest_path
                     .parent()
@@ -116,10 +123,10 @@ pub(super) fn cached_source_file_package<'a>(
                     if package_prev.manifest_path.components().count()
                         < package_curr.manifest_path.components().count()
                     {
-                        package_near = Some(package_curr);
+                        package_near = Some(package_curr.clone());
                     }
                 } else {
-                    package_near = Some(package_curr);
+                    package_near = Some(package_curr.clone());
                 }
             }
 
@@ -128,6 +135,22 @@ pub(super) fn cached_source_file_package<'a>(
         .map(|value| value as &_)
 }
 
+fn cached_directory_metadata<'a>(
+    directory_metadata_map: &'a mut BTreeMap<PathBuf, Metadata>,
+    path: &Path,
+) -> Result<&'a Metadata> {
+    directory_metadata_map
+        .entry(path.to_path_buf())
+        .or_try_insert_with(|| {
+            MetadataCommand::new()
+                .current_dir(path)
+                .no_deps()
+                .exec()
+                .map_err(Into::into)
+        })
+        .map(|value| value as &_)
+}
+
 fn fs_module_path(path: &Path) -> Result<Vec<String>> {
     let Some(path_parent) = path.parent() else {
         return Ok(Vec::new());
diff --git a/backends/src/rust/try_insert.rs b/backends/src/rust/try_insert.rs
index 16965334..86a75fdf 100644
--- a/backends/src/rust/try_insert.rs
+++ b/backends/src/rust/try_insert.rs
@@ -23,3 +23,29 @@ impl<'a, K: Ord, V, E> TryInsert<'a, V, E> for Entry<'a, K, V> {
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use anyhow::Result;
+    use std::{collections::BTreeMap, path::PathBuf};
+
+    #[test]
+    fn or_try_insert_with() {
+        let mut map = BTreeMap::new();
+        let path_buf = PathBuf::from("/");
+        let _: &mut bool = map
+            .entry(path_buf.clone())
+            .or_try_insert_with(|| -> Result<bool> { Ok(true) })
+            .unwrap();
+
+        // smoelius: Ensure `path_buf` is in `map`.
+        assert!(map.contains_key(&path_buf));
+
+        // smoelius: Ensure a second call to `or_try_insert_with` does not invoke the closure.
+        let _: &mut bool = map
+            .entry(path_buf)
+            .or_try_insert_with(|| -> Result<bool> { panic!() })
+            .unwrap();
+    }
+}
diff --git a/backends/src/rust/visitor.rs b/backends/src/rust/visitor.rs
index 80346b6c..1136aa18 100644
--- a/backends/src/rust/visitor.rs
+++ b/backends/src/rust/visitor.rs
@@ -66,10 +66,10 @@ pub(super) fn visit<'ast>(
     if let Some(error) = storage.borrow_mut().error.take() {
         return Err(error);
     }
-    let _: &Vec<String> = visitor.generic_visitor.backend.cached_source_file_flags(
-        &mut storage.borrow_mut().source_file_package_cache,
-        &visitor.generic_visitor.source_file,
-    )?;
+    let _: &Vec<String> = visitor
+        .generic_visitor
+        .backend
+        .cached_source_file_flags(&visitor.generic_visitor.source_file)?;
     visitor.generic_visitor.results()
 }
 
@@ -134,7 +134,17 @@ impl<'ast> Visit<'ast> for Visitor<'_, '_, '_, 'ast, '_> {
             assert!(self.test_ident.is_none());
             self.test_ident = Some(ident);
 
-            if let Some(test) = Test::new(self.storage, &self.generic_visitor.source_file, item) {
+            if let Some(test) = Test::new(
+                self.storage,
+                &mut self
+                    .generic_visitor
+                    .backend
+                    .source_file_fs_module_path_cache,
+                &mut self.generic_visitor.backend.source_file_package_cache,
+                &mut self.generic_visitor.backend.directory_metadata_cache,
+                &self.generic_visitor.source_file,
+                item,
+            ) {
                 let walk = self.generic_visitor.visit_test(self.storage, test);
 
                 if walk {