benchmark: check end() argument to be > 0

PR-URL: https://github.com/nodejs/node/pull/12030
Ref: https://github.com/nodejs/node/issues/11972
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

benchmark/common.js

@@ -193,6 +193,9 @@ Benchmark.prototype.end = function(operations) {
   if (typeof operations !== 'number') {
     throw new Error('called end() without specifying operation count');
   }
+  if (!process.env.NODEJS_BENCHMARK_ZERO_ALLOWED && operations <= 0) {
+    throw new Error('called end() with operation count <= 0');
+  }
 
   const time = elapsed[0] + elapsed[1] / 1e9;
   const rate = operations / time;

test/sequential/test-benchmark-net.js

@@ -15,7 +15,8 @@ const path = require('path');
 
 const runjs = path.join(__dirname, '..', '..', 'benchmark', 'run.js');
 
-const child = fork(runjs, ['--set', 'dur=0', 'net']);
+const child = fork(runjs, ['--set', 'dur=0', 'net'],
+                   {env: {NODEJS_BENCHMARK_ZERO_ALLOWED: 1}});
 child.on('exit', (code, signal) => {
   assert.strictEqual(code, 0);
   assert.strictEqual(signal, null);