Ensure test files load correct AVA installation

The main process sets the AVA_PATH environment variable to the absolute
path of the index.js file. Workers are loaded with this variable
present. When test files require the AVA module (assuming it's a version
containing this commit of course), the index.js file redirects to the
one used by the worker if necessary by comparing AVA_PATH.

The redirect required most of index.js to be moved into a separate
module (lib/main.js).

Fixes #643.

index.js

@@ -1,88 +1,8 @@
 'use strict';
-var process = require('./lib/process-adapter');
-var serializeError = require('./lib/serialize-error');
-var globals = require('./lib/globals');
-var Runner = require('./lib/runner');
-var send = process.send;
 
-var opts = globals.options;
-var runner = new Runner({
-	serial: opts.serial,
-	bail: opts.failFast,
-	match: opts.match
-});
-
-// note that test files have require('ava')
-require('./lib/test-worker').avaRequired = true;
-
-// if fail-fast is enabled, use this variable to detect
-// that no more tests should be logged
-var isFailed = false;
-
-Error.stackTraceLimit = Infinity;
-
-function test(props) {
-	if (isFailed) {
-		return;
-	}
-
-	var hasError = typeof props.error !== 'undefined';
-
-	// don't display anything if it's a passed hook
-	if (!hasError && props.type !== 'test') {
-		return;
-	}
-
-	if (hasError) {
-		props.error = serializeError(props.error);
-	} else {
-		props.error = null;
-	}
-
-	send('test', props);
-
-	if (hasError && opts.failFast) {
-		isFailed = true;
-		exit();
-	}
-}
-
-function exit() {
-	var stats = runner._buildStats();
-
-	send('results', {
-		stats: stats
-	});
+// Ensure the same AVA install is loaded by the test file as by the test worker.
+if (process.env.AVA_PATH && process.env.AVA_PATH !== __dirname) {
+	module.exports = require(process.env.AVA_PATH); // eslint-disable-line import/no-dynamic-require
+} else {
+	module.exports = require('./lib/main');
 }
-
-globals.setImmediate(function () {
-	var hasExclusive = runner.tests.hasExclusive;
-	var numberOfTests = runner.tests.tests.concurrent.length + runner.tests.tests.serial.length;
-
-	if (numberOfTests === 0) {
-		send('no-tests', {avaRequired: true});
-		return;
-	}
-
-	send('stats', {
-		testCount: numberOfTests,
-		hasExclusive: hasExclusive
-	});
-
-	runner.on('test', test);
-
-	process.on('ava-run', function (options) {
-		runner.run(options).then(exit);
-	});
-
-	process.on('ava-init-exit', function () {
-		exit();
-	});
-});
-
-module.exports = runner.test;
-
-// TypeScript imports the `default` property for
-// an ES2015 default import (`import test from 'ava'`)
-// See: https://github.com/Microsoft/TypeScript/issues/2242#issuecomment-83694181
-module.exports.default = runner.test;

lib/fork.js

@@ -30,6 +30,10 @@ if (env.NODE_PATH) {
 		.join(path.delimiter);
 }
 
+// In case the test file imports a different AVA install, the presence of this variable allows it to require this one
+// instead.
+env.AVA_PATH = path.resolve(__dirname, '..');
+
 module.exports = function (file, opts, execArgv) {
 	opts = objectAssign({
 		file: file,

lib/main.js

@@ -0,0 +1,89 @@
+'use strict';
+
+var process = require('./process-adapter');
+var serializeError = require('./serialize-error');
+var globals = require('./globals');
+var Runner = require('./runner');
+var send = process.send;
+
+var opts = globals.options;
+var runner = new Runner({
+	serial: opts.serial,
+	bail: opts.failFast,
+	match: opts.match
+});
+
+// note that test files have require('ava')
+require('./test-worker').avaRequired = true;
+
+// if fail-fast is enabled, use this variable to detect
+// that no more tests should be logged
+var isFailed = false;
+
+Error.stackTraceLimit = Infinity;
+
+function test(props) {
+	if (isFailed) {
+		return;
+	}
+
+	var hasError = typeof props.error !== 'undefined';
+
+	// don't display anything if it's a passed hook
+	if (!hasError && props.type !== 'test') {
+		return;
+	}
+
+	if (hasError) {
+		props.error = serializeError(props.error);
+	} else {
+		props.error = null;
+	}
+
+	send('test', props);
+
+	if (hasError && opts.failFast) {
+		isFailed = true;
+		exit();
+	}
+}
+
+function exit() {
+	var stats = runner._buildStats();
+
+	send('results', {
+		stats: stats
+	});
+}
+
+globals.setImmediate(function () {
+	var hasExclusive = runner.tests.hasExclusive;
+	var numberOfTests = runner.tests.tests.concurrent.length + runner.tests.tests.serial.length;
+
+	if (numberOfTests === 0) {
+		send('no-tests', {avaRequired: true});
+		return;
+	}
+
+	send('stats', {
+		testCount: numberOfTests,
+		hasExclusive: hasExclusive
+	});
+
+	runner.on('test', test);
+
+	process.on('ava-run', function (options) {
+		runner.run(options).then(exit);
+	});
+
+	process.on('ava-init-exit', function () {
+		exit();
+	});
+});
+
+module.exports = runner.test;
+
+// TypeScript imports the `default` property for
+// an ES2015 default import (`import test from 'ava'`)
+// See: https://github.com/Microsoft/TypeScript/issues/2242#issuecomment-83694181
+module.exports.default = runner.test;

test/cli.js

@@ -1,4 +1,5 @@
 'use strict';
+var fs = require('fs');
 var path = require('path');
 var childProcess = require('child_process');
 var test = require('tap').test;
@@ -7,6 +8,7 @@ var getStream = require('get-stream');
 var figures = require('figures');
 var arrify = require('arrify');
 var chalk = require('chalk');
+var mkdirp = require('mkdirp');
 var touch = require('touch');
 var proxyquire = require('proxyquire');
 var sinon = require('sinon');
@@ -368,3 +370,21 @@ test('prefers local version of ava', function (t) {
 	t.ok(debugSpy.calledWith('Using local install of AVA'));
 	t.end();
 });
+
+test('workers ensure test files load the same version of ava', function (t) {
+	var target = path.join(__dirname, 'fixture', 'ava-paths', 'target');
+
+	// Copy the index.js so the testFile imports it. It should then load the correct AVA install.
+	var targetInstall = path.join(target, 'node_modules', 'ava');
+	mkdirp.sync(targetInstall);
+	fs.writeFileSync(
+		path.join(targetInstall, 'index.js'),
+		fs.readFileSync(path.join(__dirname, '..', 'index.js'))
+	);
+
+	var testFile = path.join(target, 'test.js');
+	execCli([testFile], {dirname: path.join('fixture', 'ava-paths', 'cwd')}, function (err) {
+		t.ifError(err);
+		t.end();
+	});
+});

test/fixture/ava-paths/target/test.js

@@ -0,0 +1,5 @@
+/* eslint-disable import/no-extraneous-dependencies */
+/* eslint-disable import/no-unresolved */
+import test from 'ava';
+
+test(t => t.pass());