diff --git a/bunker/files/bunkerfile.py b/bunker/files/bunkerfile.py
index 1bd211d..dfe3217 100644
--- a/bunker/files/bunkerfile.py
+++ b/bunker/files/bunkerfile.py
@@ -78,7 +78,8 @@ class BunkeredFile(io.RawIOBase):
 		"""
 		size = None
 		if(file_.seekable()):
-			size = file_.seek(0, 2)
+			file_.seek(0, 2)
+			size = file_.tell()
 			file_.seek(0, 0)
 		return cls(file_, name, size=size, isvirtual=False, ismem=False)
 
@@ -96,9 +97,10 @@ class BunkeredFile(io.RawIOBase):
 	@classmethod
 	def from_BytesIO(cls, bytes_, name):
 		size = None
-		if(file_.seekable()):
-			size = file_.seek(0, 2)
-			file_.seek(0, 0)
+		if(bytes_.seekable()):
+			bytes_.seek(0, 2)
+			size = bytes_.tell()
+			bytes_.seek(0, 0)
 		return cls(bytes_, name, size=size, isvirtual=True, ismem=True)
 
 	@classmethod
diff --git a/bunker/files/tarfile.py b/bunker/files/tarfile.py
index 34e5776..084c6ea 100644
--- a/bunker/files/tarfile.py
+++ b/bunker/files/tarfile.py
@@ -73,7 +73,7 @@ class RewriteableTarFile(object):
 		for member in handle.getmembers():
 			if(member.name == membername):
 				continue
-			new_handle.add_file(member, handle.extractfile(member))
+			new_handle.addfile(member, handle.extractfile(member))
 		new_handle.close()
 
 	def close(self):
diff --git a/test/test_files_bunkerfile.py b/test/test_files_bunkerfile.py
index 1b1c80b..780dca2 100644
--- a/test/test_files_bunkerfile.py
+++ b/test/test_files_bunkerfile.py
@@ -1,5 +1,6 @@
 import os
 import tarfile
+from io import BytesIO
 from bunker.files.bunkerfile import BunkeredFile
 
 def test_load_from_tar(tmpdir):
@@ -27,3 +28,12 @@ def test_load_from_tar(tmpdir):
 
 	assert a.read() == b"abcdefg"
 	assert b.read() == b"foobar"
+
+def test_from_BytesIO():
+	b = BytesIO(b"foobar")
+	f = BunkeredFile.from_BytesIO(b, "test")
+
+	assert len(f) == len(b"foobar")
+	assert f.read() == b"foobar"
+
+
diff --git a/test/test_files_tarfile.py b/test/test_files_tarfile.py
index 62ff48b..18a4d00 100644
--- a/test/test_files_tarfile.py
+++ b/test/test_files_tarfile.py
@@ -1,5 +1,6 @@
 import os
 import tarfile
+import pytest
 
 from bunker.files.tarfile import RewriteableTarFile
 from bunker.files.bunkerfile import BunkeredFile
@@ -21,3 +22,75 @@ def test_create(tmpdir):
 	f = tf.get_file("__bunker_main__")
 	
 	assert f.read() == b"foobar"
+
+def test_rewrite(tmpdir):
+	tmpdname = str(tmpdir)
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = BunkeredFile.empty("__bunker_main__")
+	tf.add_file(f)
+	tf.add_file(BunkeredFile.empty("test.tx"))
+
+	f = tf.get_file("__bunker_main__")
+	f.write(b"foobar")
+	
+	tf.close()
+	
+	assert f.closed == True
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = tf.get_file("__bunker_main__")
+	f.write(b"foobaz")
+	tf.close()
+	
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = tf.get_file("__bunker_main__")
+	assert f.read() == b"foobaz"
+
+def test_writeback(tmpdir):
+	tmpdname = str(tmpdir)
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = BunkeredFile.empty("__bunker_main__")
+	tf.add_file(f)
+	tf.add_file(BunkeredFile.empty("test.tx"))
+
+	f = tf.get_file("__bunker_main__")
+	f.write(b"foobar")
+	
+	tf.close()
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = tf.get_file("__bunker_main__")
+	f.write(b"foobaz")
+	f.close()
+	tf.close()
+	
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = tf.get_file("__bunker_main__")
+	assert f.read() == b"foobaz"
+
+
+
+def test_delete(tmpdir):
+	tmpdname = str(tmpdir)
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	f = BunkeredFile.empty("__bunker_main__")
+	tf.add_file(f)
+	tf.add_file(BunkeredFile.empty("test.tx"))
+
+	f = tf.get_file("__bunker_main__")
+	f.write(b"foobar")
+	
+	tf.close()
+
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+	tf.delete_file("__bunker_main__")
+	tf.close()
+	
+	tf = RewriteableTarFile.open(os.path.join(tmpdname, "test.bunker"))
+
+	with pytest.raises(KeyError):
+		f = tf.get_file("__bunker_main__")
+