Issue 6090 - Allow use of console to be seen during tests

test/_common.js

Index: test/_common.js
===================================================================
--- a/test/_common.js
+++ b/test/_common.js
@@ -87,18 +87,18 @@
 
       throw new Error(
         "Attempt to import unknown JavaScript module " + resource
       );
     },
     reportError(e) {}
   },
   console: {
-    log() {},
-    error() {}
+    log: console.log.bind(console),
+    error: console.error.bind(console)
   },

[Wladimir Palant, 2017/11/28 12:59:39]

Just remove console here, not overriding this global will do.

[hub, 2017/11/28 15:29:33]

Done in follow up patch

   navigator: {
   },
   onShutdown: {
     add() {}
   },
   URL
 };
@@ -414,16 +414,35 @@
     Date: {
       now: () => currentTime
     }
   };
 };
 
 console.warn = console.log;
 
+exports.silenceAssertionOutput = function(test, msg)
+{
+  let msgMatch = new RegExp(`^Error: ${msg}[\r\n]`);

[Wladimir Palant, 2017/11/28 12:59:40]

1) Inserting unescaped strings into a regular expression is a footgun (consider
dots or question marks). If anything, the regular expression should be used to
extract the message, then you should use regular string comparison.

2) Parsing string representation of errors isn't a good idea either, it can
change. You have an Error object here, just look at the `error.message`
property.

[hub, 2017/11/28 15:29:33]

Done in followup patch.
we only have a string at that level. We'd need to change the error reporting.
Since this is only in the test, I consider it to be a reasonable assumption.

+  let errorHandler = globals.console.error;
+  globals.console.error = s =>
+  {
+    if (!msgMatch.test(s))
+      errorHandler(s);
+  };
+  try
+  {
+    return test();
+  }
+  finally
+  {
+    globals.console.error = errorHandler;
+  }
+};
+
 exports.setupRandomResult = function()
 {
   let randomResult = 0.5;
   Object.defineProperty(this, "randomResult", {
     get: () => randomResult,
     set: value => randomResult = value
   });