fix(tests): enforce mozlog rules in test logger

test/lib/log.js

@@ -1,7 +1,27 @@
 /* Any copyright is dedicated to the Public Domain.
  * http://creativecommons.org/publicdomain/zero/1.0/ */
 
-var noop = function () {}
+const assert = require('assert');
+
+// all the promise wrapping in tests makes it unclear who actually 
+// called mozlog incorrectly. So, record this location directly.
+function getMozlogCallerLocation() {
+  var err = new Error('getMozlogCallerLocation').stack.split('\n')[3]
+  return err
+}
+
+// no-op except check that first arg is a string, etc., a la mozlog
+var noop = function () {
+  assert(arguments.length <= 2, 'mozlog takes a maximum of 2 arguments' + 
+         ', caller: ' + getMozlogCallerLocation())
+  assert.equal(typeof arguments[0], 'string',
+               'mozlog must take a String as first argument, got: ' + 
+               JSON.stringify(arguments[0]) + ', caller: ' + getMozlogCallerLocation())
+  assert.equal(arguments[0].indexOf(' '), -1,
+               'mozlog first argument must not contain spaces, got "' +
+               JSON.stringify(arguments[0]) + '"' + 
+               ', caller: ' + getMozlogCallerLocation())
+}
 
 module.exports = {
   trace: noop,