provide clear error message when users attempt nested/async calls to …

…`test` (#961)

Fixes #948.

AVA does not support nested / async calls to `test`, but we were not providing a great error message when users attempted that.

* added failing test for expected error

* tests passed: waiting for review

* added test

* changed error message

* fixed error in test

* changed 'hasBegunRunning' to 'hasStarted'

lib/runner.js

@@ -46,6 +46,7 @@ function Runner(options) {
 
 	this.results = [];
 	this.tests = new TestCollection();
+	this.hasStarted = false;
 	this._bail = options.bail;
 	this._serial = options.serial;
 	this._match = options.match || [];
@@ -61,6 +62,11 @@ optionChain(chainableMethods, function (opts, args) {
 	var fn;
 	var macroArgIndex;
 
+	if (this.hasStarted) {
+		throw new Error('All tests and hooks must be declared synchronously in your ' +
+		'test file, and cannot be nested within other tests or hooks.');
+	}
+
 	if (typeof args[0] === 'string') {
 		title = args[0];
 		fn = args[1];
@@ -196,6 +202,8 @@ Runner.prototype.run = function (options) {
 
 	this.tests.on('test', this._addTestResult);
 
+	this.hasStarted = true;
+
 	return Promise.resolve(this.tests.build(this._bail).run()).then(this._buildStats);
 };
 

test/runner.js

@@ -13,6 +13,42 @@ test('must be called with new', function (t) {
 	t.end();
 });
 
+test('nested tests and hooks aren\'t allowed', function (t) {
+	t.plan(1);
+
+	var runner = new Runner();
+
+	runner.test(function () {
+		t.throws(function () {
+			runner.test(noop);
+		}, {message: 'All tests and hooks must be declared synchronously in your ' +
+		'test file, and cannot be nested within other tests or hooks.'});
+	});
+
+	runner.run({}).then(function () {
+		t.end();
+	});
+});
+
+test('tests must be declared synchronously', function (t) {
+	t.plan(1);
+
+	var runner = new Runner();
+
+	runner.test(function () {
+		return Promise.resolve();
+	});
+
+	runner.run({});
+
+	t.throws(function () {
+		runner.test(noop);
+	}, {message: 'All tests and hooks must be declared synchronously in your ' +
+	'test file, and cannot be nested within other tests or hooks.'});
+
+	t.end();
+});
+
 test('runner emits a "test" event', function (t) {
 	var runner = new Runner();