diff -r 000000000000 -r 6474c204b198 toolkit/devtools/server/tests/unit/test_listsources-02.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/devtools/server/tests/unit/test_listsources-02.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,49 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Check getting sources before there are any.
+ */
+
+var gDebuggee;
+var gClient;
+var gThreadClient;
+
+var gNumTimesSourcesSent = 0;
+
+function run_test()
+{
+  initTestDebuggerServer();
+  gDebuggee = addTestGlobal("test-stack");
+  gClient = new DebuggerClient(DebuggerServer.connectPipe());
+  gClient.request = (function (request) {
+    return function (aRequest, aOnResponse) {
+      if (aRequest.type === "sources") {
+        ++gNumTimesSourcesSent;
+      }
+      return request.call(this, aRequest, aOnResponse);
+    };
+  }(gClient.request));
+  gClient.connect(function () {
+    attachTestTabAndResume(gClient, "test-stack", function (aResponse, aTabClient, aThreadClient) {
+      gThreadClient = aThreadClient;
+      test_listing_zero_sources();
+    });
+  });
+  do_test_pending();
+}
+
+function test_listing_zero_sources()
+{
+  gThreadClient.getSources(function (aPacket) {
+    do_check_true(!aPacket.error);
+    do_check_true(!!aPacket.sources);
+    do_check_eq(aPacket.sources.length, 0);
+
+    do_check_true(gNumTimesSourcesSent <= 1,
+                  "Should only send one sources request at most, even though we"
+                  + " might have had to send one to determine feature support.");
+
+    finishClient(gClient);
+  });
+}