test: fix flaky test-http-client-timeout-with-data

test-http-client-timeout-with-data has failed here and there in CI on
FreeBSD and OS X. The test has a socket timeout set to 50ms and a timer
set for 100ms. However, they are not necessarily set in the same tick of
the event loop and their ordering is therefore not guaranteed.

Instead of using a timer, this change listens for an event on the
listener to know when the socket timeout has occurred and then runs the
code originally in the timer.

Additional refactoring: Replaced `process.on('exit', ...)` checks with
`common.mustCall()` and replaced usage of `assert.equal()` with
`assert.strictEqual()`.

PR-URL: https://github.com/nodejs/node/pull/10431
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-http-client-timeout-with-data.js

@@ -3,14 +3,8 @@ const common = require('../common');
 const assert = require('assert');
 const http = require('http');
 
-var ntimeouts = 0;
 var nchunks = 0;
 
-process.on('exit', function() {
-  assert.equal(ntimeouts, 1);
-  assert.equal(nchunks, 2);
-});
-
 const options = {
   method: 'GET',
   port: undefined,
@@ -21,7 +15,7 @@ const options = {
 const server = http.createServer(function(req, res) {
   res.writeHead(200, {'Content-Length': '2'});
   res.write('*');
-  setTimeout(function() { res.end('*'); }, common.platformTimeout(100));
+  server.once('timeout', common.mustCall(function() { res.end('*'); }));
 });
 
 server.listen(0, options.host, function() {
@@ -30,19 +24,19 @@ server.listen(0, options.host, function() {
   req.end();
 
   function onresponse(res) {
-    req.setTimeout(50, function() {
-      assert.equal(nchunks, 1); // should have received the first chunk by now
-      ntimeouts++;
-    });
+    req.setTimeout(50, common.mustCall(function() {
+      assert.strictEqual(nchunks, 1); // should have received the first chunk
+      server.emit('timeout');
+    }));
 
-    res.on('data', function(data) {
-      assert.equal('' + data, '*');
+    res.on('data', common.mustCall(function(data) {
+      assert.strictEqual('' + data, '*');
       nchunks++;
-    });
+    }, 2));
 
-    res.on('end', function() {
-      assert.equal(nchunks, 2);
+    res.on('end', common.mustCall(function() {
+      assert.strictEqual(nchunks, 2);
       server.close();
-    });
+    }));
   }
 });