diff --git a/ava-test/sed.js b/ava-test/sed.js
new file mode 100644
index 0000000..14f0f58
--- /dev/null
+++ b/ava-test/sed.js
@@ -0,0 +1,176 @@
+import fs from 'fs';
+
+import test from 'ava';
+
+import shell from '..';
+import utils from './utils/utils';
+
+test.beforeEach(t => {
+  t.context.tmp = utils.getTempDir();
+  shell.config.silent = true;
+  shell.cp('-r', 'resources', t.context.tmp);
+});
+
+test.afterEach.always(t => {
+  shell.rm('-rf', t.context.tmp);
+});
+
+
+//
+// Invalids
+//
+
+test('no arguments', t => {
+  const result = shell.sed();
+  t.truthy(shell.error());
+  t.is(result.code, 1);
+  t.truthy(result.stderr);
+});
+
+test('only one argument', t => {
+  const result = shell.sed(/asdf/g);
+  t.truthy(shell.error());
+  t.is(result.code, 1);
+});
+
+test('only two arguments', t => {
+  const result = shell.sed(/asdf/g, 'nada');
+  t.truthy(shell.error());
+  t.is(result.code, 1);
+});
+
+test('no such file', t => {
+  t.falsy(fs.existsSync('asdfasdf')); // sanity check
+  const result = shell.sed(/asdf/g, 'nada', 'asdfasdf');
+  t.truthy(shell.error());
+  t.is(result.code, 2);
+  t.is(result.stderr, 'sed: no such file or directory: asdfasdf');
+});
+
+// TODO(nate): flaky test
+test('if at least one file is missing, this should be an error', t => {
+  t.falsy(fs.existsSync('asdfasdf')); // sanity check
+  t.truthy(fs.existsSync(`${t.context.tmp}/file1`)); // sanity check
+  const result = shell.sed(/asdf/g, 'nada', `${t.context.tmp}/file1`, 'asdfasdf');
+  t.truthy(shell.error());
+  t.is(result.code, 2);
+  t.is(result.stderr, 'sed: no such file or directory: asdfasdf');
+});
+
+//
+// Valids
+//
+
+test('search with a string', t => {
+  const result = shell.sed('test1', 'hello', `${t.context.tmp}/file1`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello');
+});
+
+test('search with a regex', t => {
+  const result = shell.sed(/test1/, 'hello', `${t.context.tmp}/file1`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello');
+});
+
+test('replace with a number instead of a string', t => {
+  const result = shell.sed(/test1/, 1234, `${t.context.tmp}/file1`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), '1234');
+});
+
+test('replace using a function', t => {
+  const replaceFun = match => match.toUpperCase() + match;
+  const result = shell.sed(/test1/, replaceFun, `${t.context.tmp}/file1`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'TEST1test1');
+});
+
+test('-i option', t => {
+  const result = shell.sed('-i', /test1/, 'hello', `${t.context.tmp}/file1`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello');
+  t.is(shell.cat(`${t.context.tmp}/file1`).toString(), 'hello');
+});
+
+test('make sure * in regex is not globbed', t => {
+  const result = shell.sed(/alpha*beta/, 'hello', 'resources/grep/file');
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(
+    result.toString(),
+    'hello\nhowareyou\nhello\nthis line ends in.js\nlllllllllllllllll.js\n'
+  );
+});
+
+test('make sure * in string-regex is not globbed', t => {
+  const result = shell.sed('alpha*beta', 'hello', 'resources/grep/file');
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(
+    result.toString(),
+    'hello\nhowareyou\nhello\nthis line ends in.js\nlllllllllllllllll.js\n'
+  );
+});
+
+test('make sure * in regex is not globbed (matches something)', t => {
+  const result = shell.sed(/l*\.js/, '', 'resources/grep/file');
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(
+    result.toString(),
+    'alphaaaaaaabeta\nhowareyou\nalphbeta\nthis line ends in\n\n'
+  );
+});
+
+test('make sure * in string-regex is not globbed (matches something)', t => {
+  const result = shell.sed('l*\\.js', '', 'resources/grep/file');
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(
+    result.toString(),
+    'alphaaaaaaabeta\nhowareyou\nalphbeta\nthis line ends in\n\n'
+  );
+});
+
+test('multiple file names', t => {
+  const result = shell.sed('test', 'hello', `${t.context.tmp}/file1`,
+    `${t.context.tmp}/file2`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello1\nhello2');
+});
+
+test('array of file names (and try it out with a simple regex)', t => {
+  const result = shell.sed(/t.*st/, 'hello', [`${t.context.tmp}/file1`,
+    `${t.context.tmp}/file2`]);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello1\nhello2');
+});
+
+test('multiple file names, with in-place-replacement', t => {
+  const result = shell.sed('-i', 'test', 'hello', [`${t.context.tmp}/file1`,
+    `${t.context.tmp}/file2`]);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello1\nhello2');
+  t.is(shell.cat(`${t.context.tmp}/file1`).toString(), 'hello1');
+  t.is(shell.cat(`${t.context.tmp}/file2`).toString(), 'hello2');
+});
+
+test('glob file names, with in-place-replacement', t => {
+  t.is(shell.cat(`${t.context.tmp}/file1.txt`).toString(), 'test1\n');
+  t.is(shell.cat(`${t.context.tmp}/file2.txt`).toString(), 'test2\n');
+  const result = shell.sed('-i', 'test', 'hello', `${t.context.tmp}/file*.txt`);
+  t.falsy(shell.error());
+  t.is(result.code, 0);
+  t.is(result.toString(), 'hello1\n\nhello2\n'); // TODO: fix sed's behavior
+  t.is(shell.cat(`${t.context.tmp}/file1.txt`).toString(), 'hello1\n');
+  t.is(shell.cat(`${t.context.tmp}/file2.txt`).toString(), 'hello2\n');
+});
diff --git a/test/sed.js b/test/sed.js
deleted file mode 100644
index 2105dcc..0000000
--- a/test/sed.js
+++ /dev/null
@@ -1,137 +0,0 @@
-var shell = require('..');
-
-var assert = require('assert');
-var fs = require('fs');
-
-shell.config.silent = true;
-
-shell.rm('-rf', 'tmp');
-shell.mkdir('tmp');
-
-var result;
-
-//
-// Invalids
-//
-
-result = shell.sed();
-assert.ok(shell.error());
-assert.equal(result.code, 1);
-assert.ok(result.stderr);
-
-result = shell.sed(/asdf/g); // too few args
-assert.ok(shell.error());
-assert.equal(result.code, 1);
-
-result = shell.sed(/asdf/g, 'nada'); // too few args
-assert.ok(shell.error());
-assert.equal(result.code, 1);
-
-assert.equal(fs.existsSync('asdfasdf'), false); // sanity check
-result = shell.sed(/asdf/g, 'nada', 'asdfasdf'); // no such file
-assert.ok(shell.error());
-assert.equal(result.code, 2);
-assert.equal(result.stderr, 'sed: no such file or directory: asdfasdf');
-
-// if at least one file is missing, this should be an error
-shell.cp('-f', 'resources/file1', 'tmp/file1');
-assert.equal(fs.existsSync('asdfasdf'), false); // sanity check
-assert.equal(fs.existsSync('tmp/file1'), true); // sanity check
-result = shell.sed(/asdf/g, 'nada', 'tmp/file1', 'asdfasdf');
-assert.ok(shell.error());
-assert.equal(result.code, 2);
-assert.equal(result.stderr, 'sed: no such file or directory: asdfasdf');
-
-//
-// Valids
-//
-
-shell.cp('-f', 'resources/file1', 'tmp/file1');
-result = shell.sed('test1', 'hello', 'tmp/file1'); // search string
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello');
-
-result = shell.sed(/test1/, 'hello', 'tmp/file1'); // search regex
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello');
-
-result = shell.sed(/test1/, 1234, 'tmp/file1'); // numeric replacement
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), '1234');
-
-var replaceFun = function (match) {
-  return match.toUpperCase() + match;
-};
-result = shell.sed(/test1/, replaceFun, 'tmp/file1'); // replacement function
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'TEST1test1');
-
-result = shell.sed('-i', /test1/, 'hello', 'tmp/file1');
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello');
-assert.equal(shell.cat('tmp/file1').toString(), 'hello');
-
-// make sure * in regex is not globbed
-result = shell.sed(/alpha*beta/, 'hello', 'resources/grep/file');
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello\nhowareyou\nhello\nthis line ends in.js\nlllllllllllllllll.js\n');
-
-// make sure * in string-regex is not globbed
-result = shell.sed('alpha*beta', 'hello', 'resources/grep/file');
-assert.ok(!shell.error());
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello\nhowareyou\nhello\nthis line ends in.js\nlllllllllllllllll.js\n');
-
-// make sure * in regex is not globbed
-result = shell.sed(/l*\.js/, '', 'resources/grep/file');
-assert.ok(!shell.error());
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'alphaaaaaaabeta\nhowareyou\nalphbeta\nthis line ends in\n\n');
-
-// make sure * in string-regex is not globbed
-result = shell.sed('l*\\.js', '', 'resources/grep/file');
-assert.ok(!shell.error());
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'alphaaaaaaabeta\nhowareyou\nalphbeta\nthis line ends in\n\n');
-
-shell.cp('-f', 'resources/file1', 'tmp/file1');
-shell.cp('-f', 'resources/file2', 'tmp/file2');
-
-// multiple file names
-result = shell.sed('test', 'hello', 'tmp/file1', 'tmp/file2');
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello1\nhello2');
-
-// array of file names (and try it out with a simple regex)
-result = shell.sed(/t.*st/, 'hello', ['tmp/file1', 'tmp/file2']);
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello1\nhello2');
-
-// multiple file names, with in-place-replacement
-result = shell.sed('-i', 'test', 'hello', ['tmp/file1', 'tmp/file2']);
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello1\nhello2');
-assert.equal(shell.cat('tmp/file1').toString(), 'hello1');
-assert.equal(shell.cat('tmp/file2').toString(), 'hello2');
-
-// glob file names, with in-place-replacement
-shell.cp('resources/file*.txt', 'tmp/');
-assert.equal(shell.cat('tmp/file1.txt').toString(), 'test1\n');
-assert.equal(shell.cat('tmp/file2.txt').toString(), 'test2\n');
-result = shell.sed('-i', 'test', 'hello', 'tmp/file*.txt');
-assert.equal(shell.error(), null);
-assert.equal(result.code, 0);
-assert.equal(result.toString(), 'hello1\n\nhello2\n'); // TODO: fix sed's behavior
-assert.equal(shell.cat('tmp/file1.txt').toString(), 'hello1\n');
-assert.equal(shell.cat('tmp/file2.txt').toString(), 'hello2\n');
-
-shell.exit(123);