diff --git a/src/io/buf_writer.rs b/src/io/buf_writer.rs
index 2b7545a..440e270 100644
--- a/src/io/buf_writer.rs
+++ b/src/io/buf_writer.rs
@@ -1,10 +1,11 @@
-use crate::task::{Context, Poll};
-use futures_core::ready;
-use futures_io::{AsyncSeek, AsyncWrite, SeekFrom};
 use std::fmt;
-use std::io;
 use std::pin::Pin;
 
+use futures_core::ready;
+
+use crate::io::{self, Seek, SeekFrom, Write};
+use crate::task::{Context, Poll};
+
 const DEFAULT_CAPACITY: usize = 8 * 1024;
 
 /// Wraps a writer and buffers its output.
@@ -82,7 +83,7 @@ pub struct BufWriter<W> {
     written: usize,
 }
 
-impl<W: AsyncWrite> BufWriter<W> {
+impl<W: Write> BufWriter<W> {
     pin_utils::unsafe_pinned!(inner: W);
     pin_utils::unsafe_unpinned!(buf: Vec<u8>);
 
@@ -173,10 +174,6 @@ impl<W: AsyncWrite> BufWriter<W> {
         &mut self.inner
     }
 
-    //    pub fn get_pin_mut(self: Pin<&mut Self>) -> Pin<&mut W> {
-    //        self.inner()
-    //    }
-
     /// Consumes BufWriter, returning the underlying writer
     ///
     /// This method will not write leftover data, it will be lost.
@@ -187,10 +184,6 @@ impl<W: AsyncWrite> BufWriter<W> {
         self.inner
     }
 
-    //    pub fn poll_into_inner(self: Pin<&mut Self>, _cx: Context<'_>) -> Poll<io::Result<usize>> {
-    //        unimplemented!("poll into inner method")
-    //    }
-
     /// Returns a reference to the internally buffered data.
     ///
     /// # Examples
@@ -251,7 +244,7 @@ impl<W: AsyncWrite> BufWriter<W> {
     }
 }
 
-impl<W: AsyncWrite> AsyncWrite for BufWriter<W> {
+impl<W: Write> Write for BufWriter<W> {
     fn poll_write(
         mut self: Pin<&mut Self>,
         cx: &mut Context<'_>,
@@ -278,7 +271,7 @@ impl<W: AsyncWrite> AsyncWrite for BufWriter<W> {
     }
 }
 
-impl<W: AsyncWrite + fmt::Debug> fmt::Debug for BufWriter<W> {
+impl<W: Write + fmt::Debug> fmt::Debug for BufWriter<W> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("BufReader")
             .field("writer", &self.inner)
@@ -287,11 +280,10 @@ impl<W: AsyncWrite + fmt::Debug> fmt::Debug for BufWriter<W> {
     }
 }
 
-impl<W: AsyncWrite + AsyncSeek> AsyncSeek for BufWriter<W> {
+impl<W: Write + Seek> Seek for BufWriter<W> {
     /// Seek to the offset, in bytes, in the underlying writer.
     ///
     /// Seeking always writes out the internal buffer before seeking.
-
     fn poll_seek(
         mut self: Pin<&mut Self>,
         cx: &mut Context<'_>,
@@ -301,80 +293,3 @@ impl<W: AsyncWrite + AsyncSeek> AsyncSeek for BufWriter<W> {
         self.inner().poll_seek(cx, pos)
     }
 }
-
-mod tests {
-    #![allow(unused_imports)]
-
-    use super::BufWriter;
-    use crate::io::{self, SeekFrom};
-    use crate::prelude::*;
-    use crate::task;
-
-    #[test]
-    fn test_buffered_writer() {
-        task::block_on(async {
-            let inner = Vec::new();
-            let mut writer = BufWriter::with_capacity(2, inner);
-
-            writer.write(&[0, 1]).await.unwrap();
-            assert_eq!(writer.buffer(), []);
-            assert_eq!(*writer.get_ref(), [0, 1]);
-
-            writer.write(&[2]).await.unwrap();
-            assert_eq!(writer.buffer(), [2]);
-            assert_eq!(*writer.get_ref(), [0, 1]);
-
-            writer.write(&[3]).await.unwrap();
-            assert_eq!(writer.buffer(), [2, 3]);
-            assert_eq!(*writer.get_ref(), [0, 1]);
-
-            writer.flush().await.unwrap();
-            assert_eq!(writer.buffer(), []);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
-
-            writer.write(&[4]).await.unwrap();
-            writer.write(&[5]).await.unwrap();
-            assert_eq!(writer.buffer(), [4, 5]);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
-
-            writer.write(&[6]).await.unwrap();
-            assert_eq!(writer.buffer(), [6]);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5]);
-
-            writer.write(&[7, 8]).await.unwrap();
-            assert_eq!(writer.buffer(), []);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8]);
-
-            writer.write(&[9, 10, 11]).await.unwrap();
-            assert_eq!(writer.buffer(), []);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
-
-            writer.flush().await.unwrap();
-            assert_eq!(writer.buffer(), []);
-            assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
-        })
-    }
-
-    #[test]
-    fn test_buffered_writer_inner_into_inner_does_not_flush() {
-        task::block_on(async {
-            let mut w = BufWriter::with_capacity(3, Vec::new());
-            w.write(&[0, 1]).await.unwrap();
-            assert_eq!(*w.get_ref(), []);
-            let w = w.into_inner();
-            assert_eq!(w, []);
-        })
-    }
-
-    #[test]
-    fn test_buffered_writer_seek() {
-        task::block_on(async {
-            let mut w = BufWriter::with_capacity(3, io::Cursor::new(Vec::new()));
-            w.write_all(&[0, 1, 2, 3, 4, 5]).await.unwrap();
-            w.write_all(&[6, 7]).await.unwrap();
-            assert_eq!(w.seek(SeekFrom::Current(0)).await.ok(), Some(8));
-            assert_eq!(&w.get_ref().get_ref()[..], &[0, 1, 2, 3, 4, 5, 6, 7][..]);
-            assert_eq!(w.seek(SeekFrom::Start(2)).await.ok(), Some(2));
-        })
-    }
-}
diff --git a/tests/buf_writer.rs b/tests/buf_writer.rs
new file mode 100644
index 0000000..188cd8c
--- /dev/null
+++ b/tests/buf_writer.rs
@@ -0,0 +1,71 @@
+use async_std::io::{self, BufWriter, SeekFrom};
+use async_std::prelude::*;
+use async_std::task;
+
+#[test]
+fn test_buffered_writer() {
+    task::block_on(async {
+        let inner = Vec::new();
+        let mut writer = BufWriter::with_capacity(2, inner);
+
+        writer.write(&[0, 1]).await.unwrap();
+        assert_eq!(writer.buffer(), []);
+        assert_eq!(*writer.get_ref(), [0, 1]);
+
+        writer.write(&[2]).await.unwrap();
+        assert_eq!(writer.buffer(), [2]);
+        assert_eq!(*writer.get_ref(), [0, 1]);
+
+        writer.write(&[3]).await.unwrap();
+        assert_eq!(writer.buffer(), [2, 3]);
+        assert_eq!(*writer.get_ref(), [0, 1]);
+
+        writer.flush().await.unwrap();
+        assert_eq!(writer.buffer(), []);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
+
+        writer.write(&[4]).await.unwrap();
+        writer.write(&[5]).await.unwrap();
+        assert_eq!(writer.buffer(), [4, 5]);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3]);
+
+        writer.write(&[6]).await.unwrap();
+        assert_eq!(writer.buffer(), [6]);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5]);
+
+        writer.write(&[7, 8]).await.unwrap();
+        assert_eq!(writer.buffer(), []);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8]);
+
+        writer.write(&[9, 10, 11]).await.unwrap();
+        assert_eq!(writer.buffer(), []);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
+
+        writer.flush().await.unwrap();
+        assert_eq!(writer.buffer(), []);
+        assert_eq!(*writer.get_ref(), [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]);
+    })
+}
+
+#[test]
+fn test_buffered_writer_inner_into_inner_does_not_flush() {
+    task::block_on(async {
+        let mut w = BufWriter::with_capacity(3, Vec::new());
+        w.write(&[0, 1]).await.unwrap();
+        assert_eq!(*w.get_ref(), []);
+        let w = w.into_inner();
+        assert_eq!(w, []);
+    })
+}
+
+#[test]
+fn test_buffered_writer_seek() {
+    task::block_on(async {
+        let mut w = BufWriter::with_capacity(3, io::Cursor::new(Vec::new()));
+        w.write_all(&[0, 1, 2, 3, 4, 5]).await.unwrap();
+        w.write_all(&[6, 7]).await.unwrap();
+        assert_eq!(w.seek(SeekFrom::Current(0)).await.ok(), Some(8));
+        assert_eq!(&w.get_ref().get_ref()[..], &[0, 1, 2, 3, 4, 5, 6, 7][..]);
+        assert_eq!(w.seek(SeekFrom::Start(2)).await.ok(), Some(2));
+    })
+}