diff --git a/lib/stdio.js b/lib/stdio.js
new file mode 100644
index 0000000000..a429123e98
--- /dev/null
+++ b/lib/stdio.js
@@ -0,0 +1,29 @@
+'use strict';
+var util = require('util');
+
+var alias = ['stdin', 'stdout', 'stderr'];
+
+module.exports = function (opts) {
+	if (!opts) {
+		return null;
+	}
+
+	if (typeof opts.stdio === 'string') {
+		return opts.stdio;
+	}
+
+	var stdio = opts.stdio || [];
+
+	if (!Array.isArray(stdio)) {
+		throw new TypeError('Incorrect value of stdio option: ' + util.inspect(stdio));
+	}
+
+	var result = [];
+	var len = Math.max(stdio.length, alias.length);
+
+	for (var i = 0; i < len; i++) {
+		result[i] = stdio[i] || opts[alias[i]] || null;
+	}
+
+	return result;
+};
diff --git a/package.json b/package.json
index 73b57d6f8e..f98416a693 100644
--- a/package.json
+++ b/package.json
@@ -24,7 +24,8 @@
     "coveralls": "nyc report --reporter=text-lcov | coveralls"
   },
   "files": [
-    "index.js"
+    "index.js",
+    "lib"
   ],
   "keywords": [
     "exec",
diff --git a/test.js b/test/index.js
similarity index 91%
rename from test.js
rename to test/index.js
index 91bb418a93..9896b06aae 100644
--- a/test.js
+++ b/test/index.js
@@ -2,9 +2,9 @@ import path from 'path';
 import stream from 'stream';
 import test from 'ava';
 import getStream from 'get-stream';
-import m from './';
+import m from '../';
 
-process.env.PATH = path.join(__dirname, 'fixtures') + path.delimiter + process.env.PATH;
+process.env.PATH = path.join(__dirname, '..', 'fixtures') + path.delimiter + process.env.PATH;
 
 test('execa()', async t => {
 	const {stdout} = await m('noop', ['foo']);
@@ -34,12 +34,12 @@ test('stdout/stderr available on errors', async t => {
 });
 
 test('include stdout in errors for improved debugging', async t => {
-	const err = await t.throws(m('fixtures/error-message.js'));
+	const err = await t.throws(m('../fixtures/error-message.js'));
 	t.regex(err.message, /stdout/);
 });
 
 test('execa.shell()', async t => {
-	const {stdout} = await m.shell('node fixtures/noop foo');
+	const {stdout} = await m.shell('node ../fixtures/noop foo');
 	t.is(stdout, 'foo');
 });
 
@@ -54,7 +54,7 @@ test('execa.sync()', t => {
 });
 
 test('execa.shellSync()', t => {
-	const {stdout} = m.shellSync('node fixtures/noop foo');
+	const {stdout} = m.shellSync('node ../fixtures/noop foo');
 	t.is(stdout, 'foo');
 });
 
diff --git a/test/stdio.js b/test/stdio.js
new file mode 100644
index 0000000000..7da1085fd0
--- /dev/null
+++ b/test/stdio.js
@@ -0,0 +1,35 @@
+import util from 'util';
+import test from 'ava';
+import stdio from '../lib/stdio';
+
+util.inspect.styles.name = 'magenta';
+
+function t(input, expected) {
+	test(util.inspect(input, {colors: true}), t => {
+		const result = stdio(input);
+
+		if (typeof expected === 'object' && expected !== null) {
+			t.deepEqual(result, expected);
+		} else {
+			t.is(result, expected);
+		}
+	});
+}
+
+t(undefined, null);
+t(null, null);
+
+t({stdio: 'inherit'}, 'inherit');
+t({stdio: 'pipe'}, 'pipe');
+t({stdio: 'ignore'}, 'ignore');
+
+t({}, [null, null, null]);
+t({stdio: []}, [null, null, null]);
+t({stdin: 'pipe'}, ['pipe', null, null]);
+t({stdout: 'ignore'}, [null, 'ignore', null]);
+t({stderr: 'inherit'}, [null, null, 'inherit']);
+
+// precedence
+t({stdin: 'inherit', stdio: 'pipe'}, 'pipe');
+t({stdin: 'inherit', stdio: ['pipe']}, ['pipe', null, null]);
+t({stdin: 'inherit', stdio: [undefined, 'pipe']}, ['inherit', 'pipe', null]);