diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/browser_dbg_sources-cache.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/browser_dbg_sources-cache.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,142 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Tests if the sources cache knows how to cache sources when prompted.
+ */
+
+const TAB_URL = EXAMPLE_URL + "doc_function-search.html";
+const TOTAL_SOURCES = 4;
+
+let gTab, gDebuggee, gPanel, gDebugger;
+let gEditor, gSources, gControllerSources;
+let gPrevLabelsCache, gPrevGroupsCache;
+
+function test() {
+  initDebugger(TAB_URL).then(([aTab, aDebuggee, aPanel]) => {
+    gTab = aTab;
+    gDebuggee = aDebuggee;
+    gPanel = aPanel;
+    gDebugger = gPanel.panelWin;
+    gEditor = gDebugger.DebuggerView.editor;
+    gSources = gDebugger.DebuggerView.Sources;
+    gControllerSources = gDebugger.DebuggerController.SourceScripts;
+    gPrevLabelsCache = gDebugger.SourceUtils._labelsCache;
+    gPrevGroupsCache = gDebugger.SourceUtils._groupsCache;
+
+    waitForSourceShown(gPanel, "-01.js")
+      .then(initialChecks)
+      .then(getTextForSourcesAndCheckIntegrity)
+      .then(performReloadAndTestState)
+      .then(() => closeDebuggerAndFinish(gPanel))
+      .then(null, aError => {
+        ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
+      });
+  });
+}
+
+function initialChecks() {
+  ok(gEditor.getText().contains("First source!"),
+    "Editor text contents appears to be correct.");
+  is(gSources.selectedItem.attachment.label, "code_function-search-01.js",
+    "The currently selected label in the sources container is correct.");
+  ok(gSources.selectedValue.contains("code_function-search-01.js"),
+    "The currently selected value in the sources container appears to be correct.");
+
+  is(gSources.itemCount, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " sources present in the sources list.");
+  is(gSources.visibleItems.length, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " sources visible in the sources list.");
+  is(gSources.attachments.length, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " attachments stored in the sources container model.")
+  is(gSources.values.length, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " values stored in the sources container model.")
+
+  info("Source labels: " + gSources.attachments.toSource());
+  info("Source values: " + gSources.values.toSource());
+
+  is(gSources.attachments[0].label, "code_function-search-01.js",
+    "The first source label is correct.");
+  ok(gSources.values[0].contains("code_function-search-01.js"),
+    "The first source value appears to be correct.");
+
+  is(gSources.attachments[1].label, "code_function-search-02.js",
+    "The second source label is correct.");
+  ok(gSources.values[1].contains("code_function-search-02.js"),
+    "The second source value appears to be correct.");
+
+  is(gSources.attachments[2].label, "code_function-search-03.js",
+    "The third source label is correct.");
+  ok(gSources.values[2].contains("code_function-search-03.js"),
+    "The third source value appears to be correct.");
+
+  is(gSources.attachments[3].label, "doc_function-search.html",
+    "The third source label is correct.");
+  ok(gSources.values[3].contains("doc_function-search.html"),
+    "The third source value appears to be correct.");
+
+  is(gDebugger.SourceUtils._labelsCache.size, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " labels cached.");
+  is(gDebugger.SourceUtils._groupsCache.size, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " groups cached.");
+}
+
+function getTextForSourcesAndCheckIntegrity() {
+  return gControllerSources.getTextForSources(gSources.values).then(testCacheIntegrity);
+}
+
+function performReloadAndTestState() {
+  gDebugger.gTarget.once("will-navigate", testStateBeforeReload);
+  gDebugger.gTarget.once("navigate", testStateAfterReload);
+  return reloadActiveTab(gPanel, gDebugger.EVENTS.SOURCE_SHOWN);
+}
+
+function testCacheIntegrity(aSources) {
+  for (let [url, contents] of aSources) {
+    // Sources of a debugee don't always finish fetching consecutively. D'uh.
+    let index = gSources.values.indexOf(url);
+
+    ok(index >= 0 && index <= TOTAL_SOURCES,
+      "Found a source url cached correctly (" + index + ").");
+    ok(contents.contains(
+      ["First source!", "Second source!", "Third source!", "Peanut butter jelly time!"][index]),
+      "Found a source's text contents cached correctly (" + index + ").");
+
+    info("Cached source url at " + index + ": " + url);
+    info("Cached source text at " + index + ": " + contents);
+  }
+}
+
+function testStateBeforeReload() {
+  is(gSources.itemCount, 0,
+    "There should be no sources present in the sources list during reload.");
+  is(gDebugger.SourceUtils._labelsCache, gPrevLabelsCache,
+    "The labels cache has been refreshed during reload and no new objects were created.");
+  is(gDebugger.SourceUtils._groupsCache, gPrevGroupsCache,
+    "The groups cache has been refreshed during reload and no new objects were created.");
+  is(gDebugger.SourceUtils._labelsCache.size, 0,
+    "There should be no labels cached during reload");
+  is(gDebugger.SourceUtils._groupsCache.size, 0,
+    "There should be no groups cached during reload");
+}
+
+function testStateAfterReload() {
+  is(gSources.itemCount, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " sources present in the sources list.");
+  is(gDebugger.SourceUtils._labelsCache.size, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " labels cached after reload.");
+  is(gDebugger.SourceUtils._groupsCache.size, TOTAL_SOURCES,
+    "There should be " + TOTAL_SOURCES + " groups cached after reload.");
+}
+
+registerCleanupFunction(function() {
+  gTab = null;
+  gDebuggee = null;
+  gPanel = null;
+  gDebugger = null;
+  gEditor = null;
+  gSources = null;
+  gControllerSources = null;
+  gPrevLabelsCache = null;
+  gPrevGroupsCache = null;
+});