diff -r 000000000000 -r 6474c204b198 browser/devtools/sourceeditor/test/cm_comment_test.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/sourceeditor/test/cm_comment_test.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+namespace = "comment_";
+
+(function() {
+  function test(name, mode, run, before, after) {
+    return testCM(name, function(cm) {
+      run(cm);
+      eq(cm.getValue(), after);
+    }, {value: before, mode: mode});
+  }
+
+  var simpleProg = "function foo() {\n  return bar;\n}";
+
+  test("block", "javascript", function(cm) {
+    cm.blockComment(Pos(0, 3), Pos(3, 0), {blockCommentLead: " *"});
+  }, simpleProg + "\n", "/* function foo() {\n *   return bar;\n * }\n */");
+
+  test("blockToggle", "javascript", function(cm) {
+    cm.blockComment(Pos(0, 3), Pos(2, 0), {blockCommentLead: " *"});
+    cm.uncomment(Pos(0, 3), Pos(2, 0), {blockCommentLead: " *"});
+  }, simpleProg, simpleProg);
+
+  test("line", "javascript", function(cm) {
+    cm.lineComment(Pos(1, 1), Pos(1, 1));
+  }, simpleProg, "function foo() {\n//   return bar;\n}");
+
+  test("lineToggle", "javascript", function(cm) {
+    cm.lineComment(Pos(0, 0), Pos(2, 1));
+    cm.uncomment(Pos(0, 0), Pos(2, 1));
+  }, simpleProg, simpleProg);
+
+  // test("fallbackToBlock", "css", function(cm) {
+  //   cm.lineComment(Pos(0, 0), Pos(2, 1));
+  // }, "html {\n  border: none;\n}", "/* html {\n  border: none;\n} */");
+
+  // test("fallbackToLine", "ruby", function(cm) {
+  //   cm.blockComment(Pos(0, 0), Pos(1));
+  // }, "def blah()\n  return hah\n", "# def blah()\n#   return hah\n");
+
+  test("commentRange", "javascript", function(cm) {
+    cm.blockComment(Pos(1, 2), Pos(1, 13), {fullLines: false});
+  }, simpleProg, "function foo() {\n  /*return bar;*/\n}");
+
+  test("indented", "javascript", function(cm) {
+    cm.lineComment(Pos(1, 0), Pos(2), {indent: true});
+  }, simpleProg, "function foo() {\n  // return bar;\n  // }");
+
+  test("singleEmptyLine", "javascript", function(cm) {
+    cm.setCursor(1);
+    cm.execCommand("toggleComment");
+  }, "a;\n\nb;", "a;\n// \nb;");
+
+  test("dontMessWithStrings", "javascript", function(cm) {
+    cm.execCommand("toggleComment");
+  }, "console.log(\"/*string*/\");", "// console.log(\"/*string*/\");");
+
+  test("dontMessWithStrings2", "javascript", function(cm) {
+    cm.execCommand("toggleComment");
+  }, "console.log(\"// string\");", "// console.log(\"// string\");");
+
+  test("dontMessWithStrings3", "javascript", function(cm) {
+    cm.execCommand("toggleComment");
+  }, "// console.log(\"// string\");", "console.log(\"// string\");");
+})();