diff --git a/src/file.rs b/src/file.rs
new file mode 100644
index 0000000..83c6006
--- /dev/null
+++ b/src/file.rs
@@ -0,0 +1,13 @@
+use std::fs::File;
+
+pub struct FileEnv {
+    pub open: FileOpen,
+}
+impl Default for FileEnv {
+    fn default() -> Self {
+        Self {
+            open: |path| File::open(path),
+        }
+    }
+}
+pub type FileOpen = fn(path: &str) -> std::io::Result<File>;
diff --git a/src/history/find.rs b/src/history/find.rs
index 4171eb2..70162d2 100644
--- a/src/history/find.rs
+++ b/src/history/find.rs
@@ -1,11 +1,10 @@
-use crate::prelude::*;
+use crate::{file::FileEnv, prelude::*};
 
 use atom_syndication::Link;
-use std::fs::File;
 use std::io::{BufRead, BufReader};
 
-pub fn find(link: &Link, file_name: &str) -> Result<bool> {
-    if let Ok(file) = File::open(file_name) {
+pub fn find(link: &Link, file_name: &str, e: &FileEnv) -> Result<bool> {
+    if let Ok(file) = (e.open)(file_name) {
         let reader = BufReader::new(file);
         for line in reader.lines() {
             if line? == link.href {
@@ -34,9 +33,8 @@ mod test {
             title: None,
             length: None,
         };
-
         //when
-        let result = find(&link, &file_name)?;
+        let result = find(&link, &file_name, &FileEnv::default())?;
 
         //then
         drop(dir);
@@ -61,7 +59,7 @@ mod test {
         };
 
         //when
-        let result = find(&link, &file_name)?;
+        let result = find(&link, &file_name, &FileEnv::default())?;
 
         //then
         drop(dir);
@@ -88,7 +86,7 @@ mod test {
         };
 
         //when
-        let result = find(&link, &file_name)?;
+        let result = find(&link, &file_name, &FileEnv::default())?;
 
         //then
         drop(dir);
diff --git a/src/history/mod.rs b/src/history/mod.rs
index d6f7255..47f7e36 100644
--- a/src/history/mod.rs
+++ b/src/history/mod.rs
@@ -1,4 +1,4 @@
-use crate::prelude::*;
+use crate::{file::FileEnv, prelude::*};
 
 mod add;
 mod find;
@@ -13,5 +13,5 @@ pub struct HistoryEnv {
     pub add: HistoryAdd,
 }
 
-pub type HistoryFind = fn(&Link, &str) -> Result<bool>;
+pub type HistoryFind = fn(&Link, &str, &FileEnv) -> Result<bool>;
 pub type HistoryAdd = fn(&Link, &str) -> Result<()>;
diff --git a/src/lib.rs b/src/lib.rs
index ce77f4d..e51e116 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 mod errors;
 pub mod feed;
 pub mod fetch;
+pub mod file;
 pub mod history;
 pub mod prelude;
 mod subscriptions;
@@ -10,6 +11,7 @@ mod test_utils;
 
 use feed::FeedEnv;
 use fetch::FetchEnv;
+use file::FileEnv;
 use history::HistoryEnv;
 use prelude::*;
 
@@ -17,15 +19,16 @@ pub struct Env {
     pub feed: FeedEnv,
     pub history: HistoryEnv,
     pub fetch: FetchEnv,
+    pub file: FileEnv,
 }
 
 pub fn run(subscriptions: &str, history: &str, site: &str, e: Env) -> Result<()> {
-    for channel_name in subscriptions::lines_from(subscriptions)? {
+    for channel_name in subscriptions::lines_from(subscriptions, &e.file)? {
         println!("Channel: {}", channel_name);
         let feed_url = (e.feed.find)(site, &channel_name, &e.fetch.get)?;
         for entry in (e.feed.get)(&feed_url)?.entries() {
             if let Some(link) = entry.links().get(0).cloned() {
-                if !(e.history.find)(&link, history)? {
+                if !(e.history.find)(&link, history, &e.file)? {
                     println!("Downloading {}: {}", &channel_name, entry.title().as_str());
                     (e.fetch.download)(&link)?;
                     (e.history.add)(&link, history)?;
diff --git a/src/main.rs b/src/main.rs
index 8e7f6c5..5f11f1c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,4 @@
+use podal::file::FileEnv;
 use podal::prelude::*;
 
 use podal::{feed::FeedEnv, fetch::FetchEnv, history::HistoryEnv};
@@ -26,6 +27,7 @@ fn main() -> Result<()> {
                 download: podal::fetch::download,
                 get: podal::fetch::get,
             },
+            file: FileEnv::default(),
         },
     )?;
 
diff --git a/src/subscriptions.rs b/src/subscriptions.rs
index 5ecc379..edaf777 100644
--- a/src/subscriptions.rs
+++ b/src/subscriptions.rs
@@ -1,10 +1,10 @@
 use crate::prelude::*;
 
-use std::fs::File;
+use crate::file::FileEnv;
 use std::io::{BufRead, BufReader};
 
-pub fn lines_from(file_name: &str) -> Result<Vec<String>> {
-    let file = File::open(file_name)?;
+pub fn lines_from(file_name: &str, e: &FileEnv) -> Result<Vec<String>> {
+    let file = (e.open)(file_name)?;
     let reader = BufReader::new(file);
     let mut lines = vec![];
     for line in reader.lines().flatten() {
@@ -29,9 +29,10 @@ mod tests {
             "subscriptions.txt",
             include_bytes!("../test/data/subscriptions.txt"),
         )?;
+        let file_env = FileEnv::default();
 
         //when
-        let result = lines_from(&file_name)?;
+        let result = lines_from(&file_name, &file_env)?;
 
         //then
         drop(dir);
@@ -46,9 +47,10 @@ mod tests {
             "subscriptions.txt",
             include_bytes!("../test/data/subscriptions-blank-line.txt"),
         )?;
+        let file_env = FileEnv::default();
 
         //when
-        let result = lines_from(&file_name)?;
+        let result = lines_from(&file_name, &file_env)?;
 
         //then
         drop(dir);
@@ -63,9 +65,10 @@ mod tests {
             "subscriptions.txt",
             include_bytes!("../test/data/subscriptions-comment.txt"),
         )?;
+        let file_env = FileEnv::default();
 
         //when
-        let result = lines_from(&file_name)?;
+        let result = lines_from(&file_name, &file_env)?;
 
         //then
         drop(dir);