feat(test): enable dumpio in tests #2610

This patch allows logging the output of the Chromium process to be enabled in tests by passing in the environment variable `DUMPIO=true`.

Additionally, the `stderr` of the Chromium process will always be logged in the the "Output" section of failing page tests.

test/puppeteer.spec.js

@@ -206,7 +206,7 @@ module.exports.addTests = function({testRunner, expect, PROJECT_ROOT, defaultBro
         const dumpioTextToLog = 'MAGIC_DUMPIO_TEST';
         let dumpioData = '';
         const {spawn} = require('child_process');
-        const options = Object.assign({dumpio: true}, defaultBrowserOptions);
+        const options = Object.assign({}, defaultBrowserOptions, {dumpio: true});
         const res = spawn('node',
             [path.join(__dirname, 'fixtures', 'dumpio.js'), PROJECT_ROOT, JSON.stringify(options), server.EMPTY_PAGE, dumpioTextToLog]);
         res.stderr.on('data', data => dumpioData += data.toString('utf8'));

test/test.js

@@ -47,6 +47,7 @@ const defaultBrowserOptions = {
   executablePath,
   slowMo,
   headless,
+  dumpio: (process.env.DUMPIO || 'false').trim().toLowerCase() === 'true',
   args: ['--no-sandbox']
 };
 const browserWithExtensionOptions = {
@@ -120,11 +121,22 @@ describe('Page', function() {
     state.browser = null;
   });
 
-  beforeEach(async state => {
+  beforeEach(async(state, test) => {
     state.page = await state.browser.newPage();
+    const rl = require('readline').createInterface({input: state.browser.process().stderr});
+    test.output = '';
+    rl.on('line', onLine);
+    state.tearDown = () => {
+      rl.removeListener('line', onLine);
+      rl.close();
+    };
+    function onLine(line) {
+      test.output += line + '\n';
+    }
   });
 
   afterEach(async state => {
+    state.tearDown();
     await state.page.close();
     state.page = null;
   });

utils/testrunner/Reporter.js

@@ -83,6 +83,10 @@ class Reporter {
             console.log(stack.join('\n'));
           }
         }
+        if (test.output) {
+          console.log('  Output:');
+          console.log(test.output.split('\n').map(line => '    ' + line).join('\n'));
+        }
         console.log('');
       }
     }