Return thrown error/rejected promise from t.throws

lib/assert.js

@@ -78,7 +78,7 @@ x.throws = function (fn, err, msg) {
 			.then(function () {
 				x.throws(noop, err, msg);
 			}, function (fnErr) {
-				x.throws(function () {
+				return x.throws(function () {
 					throw fnErr;
 				}, err, msg);
 			});
@@ -92,7 +92,18 @@ x.throws = function (fn, err, msg) {
 			};
 		}
 
-		assert.throws(fn, err, msg);
+		var result;
+
+		assert.throws(function () {
+			try {
+				fn();
+			} catch (error) {
+				result = error;
+				throw error;
+			}
+		}, err, msg);
+
+		return result;
 	} catch (err) {
 		test(false, create(err.actual, err.expected, err.operator, err.message, x.throws));
 	}

readme.md

@@ -566,6 +566,8 @@ Assert that `function` throws an error, or `promise` rejects with an error.
 
 `error` can be a constructor, regex, error message or validation function.
 
+Returns the error thrown by `function` or the rejection reason of `promise`.
+
 ### .notThrows(function|promise, [message])
 
 Assert that `function` doesn't throw an `error` or `promise` resolves.

test/assert.js

@@ -1,5 +1,6 @@
 'use strict';
 var test = require('tap').test;
+var Promise = require('bluebird');
 var assert = require('../lib/assert');
 
 test('.pass()', function (t) {
@@ -182,6 +183,26 @@ test('.throws()', function (t) {
 	t.end();
 });
 
+test('.throws() returns the thrown error', function (t) {
+	var expected = new Error();
+	var actual = assert.throws(function () {
+		throw expected;
+	});
+
+	t.is(actual, expected);
+
+	t.end();
+});
+
+test('.throws() returns the rejection reason of promise', function (t) {
+	var expected = new Error();
+
+	assert.throws(Promise.reject(expected)).then(function (actual) {
+		t.is(actual, expected);
+		t.end();
+	});
+});
+
 test('.notThrows()', function (t) {
 	t.doesNotThrow(function () {
 		assert.notThrows(function () {});