Fix exceptions when running the tests.

Tools/GardeningServer/scripts/net_unittests.js

Index: Tools/GardeningServer/scripts/net_unittests.js
diff --git a/Tools/GardeningServer/scripts/net_unittests.js b/Tools/GardeningServer/scripts/net_unittests.js
index 193d3d4f7ce944d53ecfd56c16bf9f6195211cd4..fdb7fd263fc22d2dfc4fffe5ce8b768c6e559a7e 100644
--- a/Tools/GardeningServer/scripts/net_unittests.js
+++ b/Tools/GardeningServer/scripts/net_unittests.js
@@ -29,6 +29,8 @@ function NetworkSimulator()
     this._pendingPromises = [];
 };
 
+NetworkSimulator._testInProgress = false;
+
 NetworkSimulator.prototype.schedulePromise = function(promise) {
     this._pendingPromises.push(promise);
     return promise;
@@ -39,41 +41,62 @@ NetworkSimulator.prototype.resolvePromises = function() {
     return new Promise(function(resolve, reject) {
         var pendingPromises = self._pendingPromises;
         self._pendingPromises = [];
-        function all_resolved (results) {
+        function allResolved(results) {
             if (self._pendingPromises.length) {
                 resolve(self.resolvePromises());
                 return;
             }
             resolve(results);
         }
-        Promise.all(pendingPromises).then(all_resolved, all_resolved);
+        Promise.all(pendingPromises).then(allResolved, allResolved);
     });
 };
 
 NetworkSimulator.prototype.runTest = function(testCase)
 {
+    if (NetworkSimulator._testInProgress) {
+        ok(false, "runTest calls cannot be nested");
+        start();
+        return;
+    }
+
+    NetworkSimulator._testInProgress = true;
+
     var self = this;
-    var realNet = window.net;
     return new Promise(function(resolve, reject) {
+        var realNet = window.net;
+
+        function reset() {
+            window.net = realNet;
+            NetworkSimulator._testInProgress = false;
+        }
 
         // All net.* methods should return promises. This watches all
         // promises generated by test-overridden methods.
         window.net = {};
         ['probe', 'jsonp', 'get', 'post',
          'ajax', 'json', 'xml'].forEach(function(method) {
-             if (method in self) {
-                 net[method] = function() {
-                     return self.schedulePromise(self[method].apply(self, arguments));
-                 };
-             };
-         });
+            if (method in self) {
+                net[method] = function() {
+                    return self.schedulePromise(self[method].apply(self, arguments));
+                };
+            };
+        });
+
+        try {
+            testCase();
+        } catch(e) {
+            // Make sure errors thrown in the test case don't leave window.net in a bad state.
+            reset();
+            ok(false, "Test case threw an error:" + e);
+        }
 
-        testCase();
         self.resolvePromises().then(function() {
-            window.net = realNet;
+            reset();
             equal(window.net, realNet);
             resolve();
         }).catch(function(e) {
+            reset();
             ok(false, "Failed to finish test: " + e);
         });
     });