tests: add test for non-integer delay timers.

PR #8034 came with a test to make sure that timers expiry is based on
monotonic time and not on wall-clock time. However, a bug in the
implementation broke timers with non-integer delays. A fix for this
issue was provided with PR #8073, but it didn't come with a test.

Because #8073 fixed a subtle issue that could reappear in the future,
and because the impact of such an issue would be significant, I suggest
adding this test.

The test would timeout after 1 minute if the issue was reproduced.
Otherwise it will run very quickly.

test/simple/test-timers-non-integer-delay.js

@@ -0,0 +1,50 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+/*
+ * This test makes sure that non-integer timer delays do not make the process
+ * hang. See https://github.com/joyent/node/issues/8065 and
+ * https://github.com/joyent/node/issues/8068 which have been fixed by
+ * https://github.com/joyent/node/pull/8073.
+ *
+ * If the process hangs, this test will make the tests suite timeout,
+ * otherwise it will exit very quickly (after 50 timers with a short delay
+ * fire).
+ *
+ * We have to set at least several timers with a non-integer delay to
+ * reproduce the issue. Sometimes, a timer with a non-integer delay will
+ * expire correctly. 50 timers has always been more than enough to reproduce
+ * it 100%.
+ */
+
+var assert = require('assert');
+
+var TIMEOUT_DELAY = 1.1;
+var NB_TIMEOUTS_FIRED = 50;
+
+var nbTimeoutFired = 0;
+var interval = setInterval(function() {
+  ++nbTimeoutFired;
+  if (nbTimeoutFired === NB_TIMEOUTS_FIRED) {
+    clearInterval(interval);
+    process.exit(0);
+  }
+}, TIMEOUT_DELAY);