diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/browser_dbg_tracing-04.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/browser_dbg_tracing-04.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,84 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Test that when we click on logs, we get the parameters/return value in the variables view.
+ */
+
+const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
+
+let gTab, gDebuggee, gPanel, gDebugger;
+
+function test() {
+  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
+    initDebugger(TAB_URL).then(([aTab, aDebuggee, aPanel]) => {
+      gTab = aTab;
+      gDebuggee = aDebuggee;
+      gPanel = aPanel;
+      gDebugger = gPanel.panelWin;
+
+      waitForSourceShown(gPanel, "code_tracing-01.js")
+        .then(() => startTracing(gPanel))
+        .then(clickButton)
+        .then(() => waitForClientEvents(aPanel, "traces"))
+        .then(clickTraceCall)
+        .then(testParams)
+        .then(clickTraceReturn)
+        .then(testReturn)
+        .then(() => stopTracing(gPanel))
+        .then(() => {
+          const deferred = promise.defer();
+          SpecialPowers.popPrefEnv(deferred.resolve);
+          return deferred.promise;
+        })
+        .then(() => closeDebuggerAndFinish(gPanel))
+        .then(null, aError => {
+          DevToolsUtils.reportException("browser_dbg_tracing-04.js", aError);
+          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
+        });
+    });
+  });
+}
+
+function clickButton() {
+  EventUtils.sendMouseEvent({ type: "click" },
+                            gDebuggee.document.querySelector("button"),
+                            gDebuggee);
+}
+
+function clickTraceCall() {
+  filterTraces(gPanel, t => t.querySelector(".trace-name[value=factorial]"))[0]
+    .click();
+}
+
+function testParams() {
+  const name = gDebugger.document.querySelector(".variables-view-variable .name");
+  ok(name, "Should have a variable name");
+  is(name.getAttribute("value"), "n", "The variable name should be n");
+
+  const value = gDebugger.document.querySelector(".variables-view-variable .value.token-number");
+  ok(value, "Should have a variable value");
+  is(value.getAttribute("value"), "5", "The variable value should be 5");
+}
+
+function clickTraceReturn() {
+  filterTraces(gPanel, t => t.querySelector(".trace-name[value=factorial]"))
+    .pop().click();
+}
+
+function testReturn() {
+  const name = gDebugger.document.querySelector(".variables-view-variable .name");
+  ok(name, "Should have a variable name");
+  is(name.getAttribute("value"), "<return>", "The variable name should be <return>");
+
+  const value = gDebugger.document.querySelector(".variables-view-variable .value.token-number");
+  ok(value, "Should have a variable value");
+  is(value.getAttribute("value"), "120", "The variable value should be 120");
+}
+
+registerCleanupFunction(function() {
+  gTab = null;
+  gDebuggee = null;
+  gPanel = null;
+  gDebugger = null;
+});