always halt execution when async skip() called; closes #2465

- also fixes lack of support for async `skip()` when `allowUncaught` option is used
- adds some debuggability into `this.skip()` calls

lib/runnable.js

@@ -133,7 +133,7 @@ Runnable.prototype.enableTimeouts = function(enabled) {
  * @api public
  */
 Runnable.prototype.skip = function() {
-  throw new Pending();
+  throw new Pending('sync skip');
 };
 
 /**
@@ -298,14 +298,19 @@ Runnable.prototype.run = function(fn) {
   if (this.async) {
     this.resetTimeout();
 
+    // allows skip() to be used in an explicit async context
+    this.skip = function asyncSkip() {
+      done(new Pending('async skip call'));
+      // halt execution.  the Runnable will be marked pending
+      // by the previous call, and the uncaught handler will ignore
+      // the failure.
+      throw new Pending('async skip; aborting execution');
+    };
+
     if (this.allowUncaught) {
       return callFnAsync(this.fn);
     }
     try {
-      // allows skip() to be used in an explicit async context
-      this.skip = function() {
-        done(new Pending());
-      };
       callFnAsync(this.fn);
     } catch (err) {
       done(utils.getError(err));

lib/runner.js

@@ -309,6 +309,8 @@ Runner.prototype.hook = function(name, fn) {
             suite.tests.forEach(function(test) {
               test.pending = true;
             });
+            // a pending hook won't be executed twice.
+            hook.pending = true;
           }
         } else {
           self.failHook(hook, err);
@@ -695,8 +697,8 @@ Runner.prototype.uncaught = function(err) {
 
   runnable.clearTimeout();
 
-  // Ignore errors if complete
-  if (runnable.state) {
+  // Ignore errors if complete or pending
+  if (runnable.state || runnable.isPending()) {
     return;
   }
   this.fail(runnable, err);