Implement a "grep" option in runner.

This aims to resolve issue #476. --grep can be passed to
ava which means to skip every test that doesn't match the
supplied pattern search for the test title. The pattern
can contain regexp strings and the skipped flag will be
set based on the output of "test" (so anywhere in the
title of the test will work).

cli.js

@@ -48,6 +48,7 @@ var cli = meow([
 	'  --tap, -t        Generate TAP output',
 	'  --verbose, -v    Enable verbose output',
 	'  --no-cache       Disable the transpiler cache',
+	'  --grep, -g       Only run tests matching pattern',
 	'',
 	'Examples',
 	'  ava',
@@ -62,7 +63,8 @@ var cli = meow([
 ], {
 	string: [
 		'_',
-		'require'
+		'require',
+		'grep'
 	],
 	boolean: [
 		'fail-fast',
@@ -75,7 +77,8 @@ var cli = meow([
 		t: 'tap',
 		v: 'verbose',
 		r: 'require',
-		s: 'serial'
+		s: 'serial',
+		g: 'grep'
 	}
 });
 
@@ -90,6 +93,7 @@ var api = new Api(cli.input.length ? cli.input : arrify(conf.files), {
 	failFast: cli.flags.failFast,
 	serial: cli.flags.serial,
 	require: arrify(cli.flags.require),
+	grep: cli.flags.grep,
 	cacheEnabled: cli.flags.cache !== false
 });
 

lib/runner.js

@@ -47,6 +47,15 @@ function Runner(opts) {
 	EventEmitter.call(this);
 
 	this.options = opts || {};
+
+	if (this.options.grep instanceof RegExp) {
+		this.grep = this.options.grep;
+	} else if (typeof this.options.grep === 'string') {
+		this.grep = new RegExp(this.options.grep);
+	} else {
+		this.grep = new RegExp('');
+	}
+
 	this.results = [];
 	this.tests = [];
 	this.testsByType = {};
@@ -57,6 +66,10 @@ util.inherits(Runner, EventEmitter);
 module.exports = Runner;
 
 optionChain(chainableMethods, function (opts, title, fn) {
+	if (!opts.skipped && !this.grep.test(title)) {
+		console.log(title);
+	}
+	opts.skipped = opts.skipped || !this.grep.test(title);
 	var Constructor = (opts && /Each/.test(opts.type)) ? Hook : Test;
 	var test = new Constructor(title, fn);
 	test.metadata = objectAssign({}, opts);

test/runner.js

@@ -333,3 +333,55 @@ test('only test', function (t) {
 		t.end();
 	});
 });
+
+test('skip test based on grep option with string', function (t) {
+	t.plan(3);
+
+	var runner = new Runner({
+		grep: 'dont skip me'
+	});
+
+	runner.test('skip me1', function () {
+		t.fail();
+	});
+
+	runner.skip('skip me2', function () {
+		t.fail();
+	});
+
+	runner.test('dont skip me', function () {
+		t.pass();
+	});
+
+	runner.run().then(function () {
+		t.is(runner.stats.passCount, 1);
+		t.is(runner.stats.failCount, 0);
+		t.end();
+	});
+});
+
+test('skip test based on grep option with RegExp', function (t) {
+	t.plan(3);
+
+	var runner = new Runner({
+		grep: new RegExp('dont skip me')
+	});
+
+	runner.test('skip me1', function () {
+		t.fail();
+	});
+
+	runner.skip('skip me2', function () {
+		t.fail();
+	});
+
+	runner.test('dont skip me', function () {
+		t.pass();
+	});
+
+	runner.run().then(function () {
+		t.is(runner.stats.passCount, 1);
+		t.is(runner.stats.failCount, 0);
+		t.end();
+	});
+});