diff --git a/src/io.rs b/src/io.rs
index f7bacfd..88f777d 100644
--- a/src/io.rs
+++ b/src/io.rs
@@ -1,5 +1,5 @@
 use std::fs::{File, OpenOptions};
-use std::io::{self, BufRead, BufReader, BufWriter, Write};
+use std::io::{stdin, stdout, BufRead, BufReader, BufWriter, Write};
 use std::path::Path;
 
 fn open_input_file(file_name: &str) -> Result<Box<dyn BufRead>, String> {
@@ -17,7 +17,7 @@ fn open_input_file(file_name: &str) -> Result<Box<dyn BufRead>, String> {
 }
 
 fn open_stdin() -> Result<Box<dyn BufRead>, String> {
-    Ok(Box::new(BufReader::new(io::stdin())))
+    return Ok(Box::new(BufReader::new(stdin())));
 }
 
 fn open_input(input: Option<String>) -> Result<Box<dyn BufRead>, String> {
@@ -36,7 +36,7 @@ fn open_output_file(output: &str) -> Result<Box<dyn Write>, String> {
 }
 
 fn open_stdout() -> Result<Box<dyn Write>, String> {
-    Ok(Box::new(BufWriter::new(io::stdout())))
+    Ok(Box::new(BufWriter::new(stdout())))
 }
 
 fn open_output(output: Option<String>) -> Result<Box<dyn Write>, String> {
@@ -58,7 +58,6 @@ pub fn open(
 
 mod tests {
     use super::*;
-    use std::fs;
 
     #[test]
     fn test_input_with_none() {
@@ -88,7 +87,7 @@ mod tests {
     fn test_output_with_not_exist_file() {
         let output = open_output(Some("testdata/not_exist_file.txt".to_string()));
         assert!(output.is_ok());
-        let _ = fs::remove_file("testdata/not_exist_file.txt");
+        let _ = std::fs::remove_file("testdata/not_exist_file.txt");
     }
 
     #[test]
diff --git a/src/uniqer.rs b/src/uniqer.rs
index 280ffff..5a98e96 100644
--- a/src/uniqer.rs
+++ b/src/uniqer.rs
@@ -170,4 +170,20 @@ mod tests {
         assert!(uniqer.next("previous".to_string()).is_some());
         assert!(uniqer.next("hogehoge".to_string()).is_some());
     }
+
+    use std::fs::File;
+    use std::io::BufReader;
+    use std::vec::Vec;
+
+    #[test]
+    fn test_filter() {
+        let dest: Vec<u8> = vec![];
+        let mut uniqer = construct_uniqer(false, false, false);
+        let input = BufReader::new(File::open("testdata/test1.txt").unwrap());
+        let mut input_box: Box<dyn BufRead> = Box::new(input);
+        let mut output_box: Box<dyn Write> = Box::new(dest);
+        // uniqer.filter(&mut input_box, &mut output_box);
+        // How do I get the result from  written to the memory??
+        // String::from_utf8(dest).unwrap();
+    }
 }