--- a/dom/imptests/README
+++ b/dom/imptests/README
@@ -44,16 +44,20 @@ Source;  Usage and purpose;  License
 
 * importTestsuite.py
   Imports a test suite from a remote repository. Takes one argument, a file in
   the format described under webapps.txt.
   Note: removes both source and destination directory before starting. Do not
         use with outstanding changes in either directory.
   MPL
 
+* writeMakefile.py
+  Helper functions to write out Makefiles.
+  MPL
+
 * Makefile.in
   Integration with our build system. Installs support files into /resources and
   includes a .mk file for each repository.
   MPL
 
 * failures/
   Expected failures for tests in each repository.  Each test's failures, if
   any, are in a file with the same path and name with .json appended.  New

--- a/dom/imptests/editing/Makefile.in
+++ b/dom/imptests/editing/Makefile.in
@@ -11,18 +11,15 @@ DIRS = \
   css \
   conformancetest \
   selecttest \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
-  $(NULL)
-
-_TESTS += \
+_FILES = \
   implementation.js \
   tests.js \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/editing/conformancetest/Makefile.in
+++ b/dom/imptests/editing/conformancetest/Makefile.in
@@ -8,19 +8,16 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/editing/conformancetest
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_runtest.html \
   test_event.html \
-  $(NULL)
-
-_TESTS += \
   data.js \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/editing/css/Makefile.in
+++ b/dom/imptests/editing/css/Makefile.in
@@ -8,17 +8,14 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/editing/css
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
-  $(NULL)
-
-_TESTS += \
+_FILES = \
   reset.css \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/editing/selecttest/Makefile.in
+++ b/dom/imptests/editing/selecttest/Makefile.in
@@ -8,30 +8,27 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/editing/selecttest
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_addRange.html \
   test_collapse.html \
   test_collapseToStartEnd.html \
   test_deleteFromDocument.html \
   test_Document-open.html \
   test_extend.html \
   test_getRangeAt.html \
   test_getSelection.html \
   test_interfaces.html \
   test_isCollapsed.html \
   test_removeAllRanges.html \
   test_selectAllChildren.html \
-  $(NULL)
-
-_TESTS += \
   common.js \
   test-iframe.html \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/html/tests/submission/Mozilla/Makefile.in
+++ b/dom/imptests/html/tests/submission/Mozilla/Makefile.in
@@ -8,24 +8,21 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/html/tests/submission/Mozilla
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_body-onload.html \
   test_pageload-image.html \
   test_pageload-video.html \
   test_script-for-onload.html \
   test_window-onerror-parse-error.html \
   test_window-onerror-runtime-error.html \
   test_window-onerror-runtime-error-throw.html \
-  $(NULL)
-
-_TESTS += \
   nested-document-write-external.js \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/html/tests/submission/Opera/microdata/Makefile.in
+++ b/dom/imptests/html/tests/submission/Opera/microdata/Makefile.in
@@ -8,17 +8,14 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/html/tests/submission/Opera/microdata
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_001.html \
   $(NULL)
 
-_TESTS += \
-  $(NULL)
-
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/importTestsuite.py
+++ b/dom/imptests/importTestsuite.py
@@ -12,16 +12,17 @@ Note: removes both source and destinatio
 
 import os
 import shutil
 import string
 import subprocess
 import sys
 
 import parseManifest
+import writeMakefile
 
 def parseManifestFile(dest, dir):
   subdirs, mochitests, _, __, supportfiles = parseManifest.parseManifestFile("hg-%s/%s/MANIFEST" % (dest, dir))
   return subdirs, mochitests, supportfiles
 
 def getData(confFile):
   """This function parses a file of the form
   URL of remote repository|Name of the destination directory
@@ -72,88 +73,50 @@ def copy(thissrcdir, dest, directories):
 
     if len(subdirs):
       if d:
         importDirs(thissrcdir, dest, ["%s/%s" % (d, subdir) for subdir in subdirs])
       else:
         # Empty directory, i.e., the repository root
         importDirs(thissrcdir, dest, subdirs)
 
-def makefileString(entries):
-  if not len(entries):
-    return "  $(NULL)"
-  return "\n".join(["  %s \\" % (entry, ) for entry in entries]) + "\n  $(NULL)"
-
 def printMakefile(dest, directories):
   """Create a .mk file to be included into the main Makefile.in, which lists the
   directories with tests.
   """
   print "Creating .mk..."
   path = dest + ".mk"
   fp = open(path, "wb")
   fp.write("DIRS += \\\n")
-  fp.write(makefileString([makePath(dest, d) for d in directories]))
+  fp.write(writeMakefile.makefileString([makePath(dest, d) for d in directories]))
   fp.write("\n")
   fp.close()
   subprocess.check_call(["hg", "add", path])
 
-makefileTemplate = """# THIS FILE IS AUTOGENERATED BY importTestsuite.py - DO NOT EDIT
-
-DEPTH = ${depth}
-
-topsrcdir = @top_srcdir@
-srcdir = @srcdir@
-VPATH = @srcdir@
-relativesrcdir = ${relativesrcdir}
-
-DIRS = \\
-${dirs}
-
-include $$(DEPTH)/config/autoconf.mk
-include $$(topsrcdir)/config/rules.mk
-"""
-testsTemplate = """
-_TESTS = \\
-${tests}
-
-_TESTS += \\
-${support}
-
-libs:: $$(_TESTS)
-\t$$(INSTALL) $$(foreach f,$$^,"$$f") $$(DEPTH)/_tests/testing/mochitest/tests/$$(relativesrcdir)
-"""
-
 def printMakefiles(thissrcdir, dest, directories):
   """Create Makefile.in files for each directory that contains tests we import.
   """
   print "Creating Makefile.ins..."
   for d in directories:
     if d:
       path = "%s/%s" % (dest, d)
     else:
       # Empty directory, i.e., the repository root
       path = dest
-    abspath = "%s/%s" % (thissrcdir, path)
     print "Creating Makefile.in in %s..." % (path, )
 
     subdirs, mochitests, supportfiles = parseManifestFile(dest, d)
 
-    fp = open(path + "/Makefile.in", "wb")
-    result = string.Template(makefileTemplate).substitute({
-      "depth": "..%s" % ("/.." * abspath.count("/"), ),
-      "relativesrcdir": "%s/%s" % (thissrcdir, path),
-      "dirs": makefileString(subdirs)
-    })
+    abspath = "%s/%s" % (thissrcdir, path)
+    files = ["test_%s" % (mochitest, ) for mochitest in mochitests]
+    files.extend(supportfiles)
 
-    if len(mochitests) + len(supportfiles):
-      result += string.Template(testsTemplate).substitute({
-        "tests": makefileString(["test_%s" % (mochitest, ) for mochitest in mochitests]),
-        "support": makefileString(supportfiles)
-      })
+    result = writeMakefile.substMakefile("importTestsuite.py", abspath, subdirs, files)
 
+    fp = open(path + "/Makefile.in", "wb")
     fp.write(result)
     fp.close()
 
 def hgadd(dest, directories):
   """Inform hg of the files in |directories|."""
   print "hg addremoving..."
   for d in directories:
     subprocess.check_call(["hg", "addremove", "%s/%s" % (dest, d)])

--- a/dom/imptests/webapps/DOMCore/tests/approved/Makefile.in
+++ b/dom/imptests/webapps/DOMCore/tests/approved/Makefile.in
@@ -8,34 +8,31 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/webapps/DOMCore/tests/approved
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_interfaces.html \
   test_Range-cloneContents.html \
   test_Range-cloneRange.html \
   test_Range-collapse.html \
   test_Range-commonAncestorContainer.html \
   test_Range-compareBoundaryPoints.html \
   test_Range-comparePoint.html \
   test_Range-deleteContents.html \
   test_Range-extractContents.html \
   test_Range-insertNode.html \
   test_Range-intersectsNode.html \
   test_Range-isPointInRange.html \
   test_Range-mutations.html \
   test_Range-selectNode.html \
   test_Range-set.html \
   test_Range-surroundContents.html \
-  $(NULL)
-
-_TESTS += \
   common.js \
   Range-test-iframe.html \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/webapps/DOMCore/tests/submissions/Opera/Makefile.in
+++ b/dom/imptests/webapps/DOMCore/tests/submissions/Opera/Makefile.in
@@ -8,17 +8,17 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/webapps/DOMCore/tests/submissions/Opera
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_getElementsByClassName-01.htm \
   test_getElementsByClassName-02.htm \
   test_getElementsByClassName-03.htm \
   test_getElementsByClassName-04.htm \
   test_getElementsByClassName-05.htm \
   test_getElementsByClassName-06.htm \
   test_getElementsByClassName-07.htm \
   test_getElementsByClassName-08.htm \
@@ -29,13 +29,10 @@ include $(topsrcdir)/config/rules.mk
   test_getElementsByClassName-13.htm \
   test_getElementsByClassName-14.htm \
   test_getElementsByClassName-15.htm \
   test_getElementsByClassName-16.htm \
   test_getElementsByClassName-17.htm \
   test_getElementsByClassName-18.htm \
   $(NULL)
 
-_TESTS += \
-  $(NULL)
-
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/webapps/WebStorage/tests/submissions/Infraware/Makefile.in
+++ b/dom/imptests/webapps/WebStorage/tests/submissions/Infraware/Makefile.in
@@ -9,17 +9,17 @@ relativesrcdir = dom/imptests/webapps/We
 
 DIRS = \
   iframe \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_event_constructor.html \
   test_event_local_key.html \
   test_event_local_newvalue.html \
   test_event_local_oldvalue.html \
   test_event_local_storagearea.html \
   test_event_local_storageeventinit.html \
   test_event_local_url.html \
   test_event_session_key.html \
@@ -38,13 +38,10 @@ include $(topsrcdir)/config/rules.mk
   test_storage_session_clear.html \
   test_storage_session_getitem.html \
   test_storage_session_key.html \
   test_storage_session_length.html \
   test_storage_session_removeitem.html \
   test_storage_session_setitem.html \
   $(NULL)
 
-_TESTS += \
-  $(NULL)
-
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/webapps/WebStorage/tests/submissions/Infraware/iframe/Makefile.in
+++ b/dom/imptests/webapps/WebStorage/tests/submissions/Infraware/iframe/Makefile.in
@@ -8,23 +8,20 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/webapps/WebStorage/tests/submissions/Infraware/iframe
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
-  $(NULL)
-
-_TESTS += \
+_FILES = \
   local_change_item_iframe.html \
   local_security_iframe.html \
   local_set_item_clear_iframe.html \
   local_set_item_iframe.html \
   session_change_item_iframe.html \
   session_set_item_clear_iframe.html \
   session_set_item_iframe.html \
   $(NULL)
 
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/webapps/WebStorage/tests/submissions/Ms2ger/Makefile.in
+++ b/dom/imptests/webapps/WebStorage/tests/submissions/Ms2ger/Makefile.in
@@ -8,17 +8,17 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/webapps/WebStorage/tests/submissions/Ms2ger
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_event_constructor_js.html \
   test_missing_arguments.html \
   test_storage_local_clear_js.html \
   test_storage_local_getitem_js.html \
   test_storage_local_index_js.html \
   test_storage_local_in_js.html \
   test_storage_local_length_js.html \
   test_storage_local_removeitem_js.html \
@@ -27,13 +27,10 @@ include $(topsrcdir)/config/rules.mk
   test_storage_session_getitem_js.html \
   test_storage_session_index_js.html \
   test_storage_session_in_js.html \
   test_storage_session_length_js.html \
   test_storage_session_removeitem_js.html \
   test_storage_session_setitem_js.html \
   $(NULL)
 
-_TESTS += \
-  $(NULL)
-
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

--- a/dom/imptests/webapps/XMLHttpRequest/tests/submissions/Ms2ger/Makefile.in
+++ b/dom/imptests/webapps/XMLHttpRequest/tests/submissions/Ms2ger/Makefile.in
@@ -8,18 +8,15 @@ VPATH = @srcdir@
 relativesrcdir = dom/imptests/webapps/XMLHttpRequest/tests/submissions/Ms2ger
 
 DIRS = \
   $(NULL)
 
 include $(DEPTH)/config/autoconf.mk
 include $(topsrcdir)/config/rules.mk
 
-_TESTS = \
+_FILES = \
   test_interfaces.html \
   test_setrequestheader-invalid-arguments.htm \
   $(NULL)
 
-_TESTS += \
-  $(NULL)
-
-libs:: $(_TESTS)
+libs:: $(_FILES)
 	$(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(relativesrcdir)

new file mode 100644
--- /dev/null
+++ b/dom/imptests/writeMakefile.py
@@ -0,0 +1,49 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import string
+
+makefileTemplate = """# THIS FILE IS AUTOGENERATED BY ${caller} - DO NOT EDIT
+
+DEPTH = ${depth}
+
+topsrcdir = @top_srcdir@
+srcdir = @srcdir@
+VPATH = @srcdir@
+relativesrcdir = ${relativesrcdir}
+
+DIRS = \\
+${dirs}
+
+include $$(DEPTH)/config/autoconf.mk
+include $$(topsrcdir)/config/rules.mk
+"""
+
+filesTemplate = """
+_FILES = \\
+${files}
+
+libs:: $$(_FILES)
+\t$$(INSTALL) $$(foreach f,$$^,"$$f") $$(DEPTH)/_tests/testing/mochitest/tests/$$(relativesrcdir)
+"""
+
+def makefileString(entries):
+  if not len(entries):
+    return "  $(NULL)"
+  return "\n".join(["  %s \\" % (entry, ) for entry in entries]) + "\n  $(NULL)"
+
+def substMakefile(caller, path, subdirs, files):
+  result = string.Template(makefileTemplate).substitute({
+    "caller": caller,
+    "depth": "..%s" % ("/.." * path.count("/"), ),
+    "relativesrcdir": path,
+    "dirs": makefileString(subdirs)
+  })
+
+  if files:
+    result += string.Template(filesTemplate).substitute({
+      "files": makefileString(files)
+    })
+
+  return result