test: improve control flow in test-tls-dhe

If this test fails, e.g., if the s_client output does not match the
expectation, the previous implementation would not produce any helpful
error messages. Rework the control flow to be more idiomatic. Avoid
callback chaining and stream operations.
Also, the TLS server 'close' event does not pass an error to the event
handler, so remove the respective assertion.
PR-URL: #46751
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: tniessen

test/parallel/test-tls-dhe.js

@@ -29,14 +29,13 @@ if (!common.opensslCli)
 common.skip('missing openssl-cli');
 
 constassert=require('assert');
+const{ once }=require('events');
 consttls=require('tls');
-constspawn=require('child_process').spawn;
+const{ execFile }=require('child_process');
 constfixtures=require('../common/fixtures');
 
 constkey=fixtures.readKey('agent2-key.pem');
 constcert=fixtures.readKey('agent2-cert.pem');
-letnsuccess=0;
-letntests=0;
 constciphers='DHE-RSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256';
 
 // Test will emit a warning because the DH parameter size is < 2048 bits
@@ -48,7 +47,7 @@ function loadDHParam(n) {
 returnfixtures.readKey(keyname);
 }
 
-functiontest(keylen,expectedCipher,cb){
+functiontest(keylen,expectedCipher){
 constoptions={
 key: key,
 cert: cert,
@@ -57,61 +56,29 @@ function test(keylen, expectedCipher, cb) {
 maxVersion: 'TLSv1.2',
 };
 
-constserver=tls.createServer(options,function(conn){
-conn.end();
-});
+constserver=tls.createServer(options,(conn)=>conn.end());
 
-server.on('close',function(err){
-assert.ifError(err);
-if(cb)cb();
-});
-
-server.listen(0,'127.0.0.1',function(){
-constargs=['s_client','-connect',`127.0.0.1:${this.address().port}`,
+server.listen(0,'127.0.0.1',common.mustCall(()=>{
+constargs=['s_client','-connect',`127.0.0.1:${server.address().port}`,
 '-cipher',ciphers];
 
-constclient=spawn(common.opensslCli,args);
-letout='';
-client.stdout.setEncoding('utf8');
-client.stdout.on('data',function(d){
-out+=d;
-});
-client.stdout.on('end',function(){
+execFile(common.opensslCli,args,common.mustSucceed((stdout)=>{
 assert(keylen==='error'||
-out.includes(`Server Temp Key: DH, ${keylen} bits`));
-constreg=newRegExp(`Cipher : ${expectedCipher}`);
-if(reg.test(out)){
-nsuccess++;
-server.close();
-}
-});
-});
-}
-
-functiontest512(){
-assert.throws(function(){
-test(512,'DHE-RSA-AES128-SHA256',null);
-},/DHparameterislessthan1024bits/);
-}
+stdout.includes(`Server Temp Key: DH, ${keylen} bits`));
+assert(stdout.includes(`Cipher : ${expectedCipher}`));
+server.close();
+}));
+}));
 
-functiontest1024(){
-test(1024,'DHE-RSA-AES128-SHA256',test2048);
-ntests++;
+returnonce(server,'close');
 }
 
-functiontest2048(){
-test(2048,'DHE-RSA-AES128-SHA256',testError);
-ntests++;
-}
-
-functiontestError(){
-test('error','ECDHE-RSA-AES128-SHA256',test512);
-ntests++;
-}
-
-test1024();
+(async()=>{
+assert.throws(()=>{
+test(512,'DHE-RSA-AES128-SHA256');
+},/DHparameterislessthan1024bits/);
 
-process.on('exit',function(){
-assert.strictEqual(ntests,nsuccess);
-assert.strictEqual(ntests,3);
-});
+awaittest(1024,'DHE-RSA-AES128-SHA256');
+awaittest(2048,'DHE-RSA-AES128-SHA256');
+awaittest('error','ECDHE-RSA-AES128-SHA256');
+})().then(common.mustCall());