Fix error on invalid concurrency (#35)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Author: sethp

index.js

@@ -3,7 +3,7 @@ const pTry = require('p-try');
 
 const pLimit = concurrency => {
 	if (!((Number.isInteger(concurrency) || concurrency === Infinity) && concurrency > 0)) {
-		return Promise.reject(new TypeError('Expected `concurrency` to be a number from 1 and up'));
+		throw new TypeError('Expected `concurrency` to be a number from 1 and up');
 	}
 
 	const queue = [];

test.js

@@ -138,10 +138,24 @@ test('clearQueue', async t => {
 	t.is(limit.pendingCount, 0);
 });
 
-test('throws on invalid concurrency argument', async t => {
-	await t.throwsAsync(pLimit(0));
-	await t.throwsAsync(pLimit(-1));
-	await t.throwsAsync(pLimit(1.2));
-	await t.throwsAsync(pLimit(undefined));
-	await t.throwsAsync(pLimit(true));
+test('throws on invalid concurrency argument', t => {
+	t.throws(() => {
+		pLimit(0);
+	});
+
+	t.throws(() => {
+		pLimit(-1);
+	});
+
+	t.throws(() => {
+		pLimit(1.2);
+	});
+
+	t.throws(() => {
+		pLimit(undefined);
+	});
+
+	t.throws(() => {
+		pLimit(true);
+	});
 });