--- a/browser/Makefile.in
+++ b/browser/Makefile.in
@@ -9,11 +9,8 @@ ifdef MAKENSISU
 # For Windows build the uninstaller during the application build since the
 # uninstaller is included with the application for mar file generation.
 libs::
 	$(MAKE) -C installer/windows uninstaller
 ifdef MOZ_MAINTENANCE_SERVICE
 	$(MAKE) -C installer/windows maintenanceservice_installer
 endif
 endif
-
-check::
-	$(PYTHON) $(topsrcdir)/build/compare-mozconfig/compare-mozconfigs-wrapper.py

--- a/build/moz.build
+++ b/build/moz.build
@@ -39,8 +39,12 @@ if CONFIG['MOZ_BUILD_APP'] == 'browser':
 if CONFIG['MOZ_APP_PROFILE']:
     DEFINES['MOZ_APP_PROFILE'] = CONFIG['MOZ_APP_PROFILE']
 
 for var in ('MOZ_CRASHREPORTER', 'MOZ_PROFILE_MIGRATOR',
             'MOZ_EXTENSION_MANAGER', 'MOZ_APP_STATIC_INI'):
     if CONFIG[var]:
         DEFINES[var] = True
 
+if CONFIG['MOZ_BUILD_APP'] == 'browser':
+    PYTHON_UNIT_TESTS += [
+        'compare-mozconfig/compare-mozconfigs-wrapper.py',
+    ]

--- a/config/Makefile.in
+++ b/config/Makefile.in
@@ -34,18 +34,16 @@ ifndef JS_STANDALONE
 HEADERS_FILES = \
 	$(DEPTH)/mozilla-config.h \
 	$(NULL)
 HEADERS_DEST := $(DIST)/include
 HEADERS_TARGET := export
 INSTALL_TARGETS += HEADERS
 endif
 
-PYTHON_UNIT_TESTS := $(wildcard $(srcdir)/tests/unit-*.py)
-
 include $(topsrcdir)/config/rules.mk
 
 HOST_CFLAGS += -DUNICODE -D_UNICODE
 
 ifndef JS_STANDALONE
 # Generate a new buildid every time we "export" in config... that's only
 # supposed to be once per-build!
 export::

--- a/config/config.mk
+++ b/config/config.mk
@@ -60,16 +60,17 @@ endif
   LIBRARY_NAME \
   LIBS \
   MAKE_FRAMEWORK \
   MODULE \
   MSVC_ENABLE_PGO \
   NO_DIST_INSTALL \
   PARALLEL_DIRS \
   PROGRAM \
+  PYTHON_UNIT_TESTS \
   RESOURCE_FILES \
   SDK_HEADERS \
   SDK_LIBRARY \
   SHARED_LIBRARY_LIBS \
   SHARED_LIBRARY_NAME \
   SIMPLE_PROGRAMS \
   SONAME \
   STATIC_LIBRARY_NAME \

--- a/config/moz.build
+++ b/config/moz.build
@@ -23,8 +23,15 @@ if CONFIG['HOST_OS_ARCH'] != 'WINNT':
     ]
     HOST_PROGRAM = 'nsinstall_real'
 
 if CONFIG['GKMEDIAS_SHARED_LIBRARY']:
     DEFINES['GKMEDIAS_SHARED_LIBRARY'] = True
 
 if CONFIG['MOZ_SHARED_ICU']:
     DEFINES['MOZ_SHARED_ICU'] = True
+
+PYTHON_UNIT_TESTS += [
+    'tests/unit-expandlibs.py',
+    'tests/unit-mozunit.py',
+    'tests/unit-nsinstall.py',
+    'tests/unit-printprereleasesuffix.py',
+]

--- a/dom/bindings/Makefile.in
+++ b/dom/bindings/Makefile.in
@@ -19,18 +19,16 @@ CPPSRCS += $(globalgen_sources) $(unifie
 # Generated bindings reference *Binding.h, not mozilla/dom/*Binding.h. And,
 # since we generate exported bindings directly to $(DIST)/include, we need
 # to add that path to the search list.
 #
 # Ideally, binding generation uses the prefixed header file names.
 # Bug 932092 tracks.
 LOCAL_INCLUDES += -I$(DIST)/include/mozilla/dom
 
-PYTHON_UNIT_TESTS += $(srcdir)/mozwebidlcodegen/test/test_mozwebidlcodegen.py
-
 include $(topsrcdir)/config/rules.mk
 
 # TODO This list should be emitted to a .pp file via
 # GenerateCSS2PropertiesWebIDL.py.
 css2properties_dependencies = \
   $(topsrcdir)/layout/style/nsCSSPropList.h \
   $(topsrcdir)/layout/style/nsCSSPropAliasList.h \
   $(webidl_base)/CSS2Properties.webidl.in \

--- a/dom/bindings/moz.build
+++ b/dom/bindings/moz.build
@@ -91,8 +91,12 @@ if CONFIG['MOZ_AUDIO_CHANNEL_MANAGER']:
 FINAL_LIBRARY = 'xul'
 
 SPHINX_TREES['webidl'] = 'docs'
 SPHINX_PYTHON_PACKAGE_DIRS += ['mozwebidlcodegen']
 
 if CONFIG['MOZ_BUILD_APP'] in ['browser', 'mobile/android', 'xulrunner']:
     # This is needed for Window.webidl
     DEFINES['HAVE_SIDEBAR'] = True
+
+PYTHON_UNIT_TESTS += [
+    'mozwebidlcodegen/test/test_mozwebidlcodegen.py',
+]

deleted file mode 100644
--- a/python/Makefile.in
+++ /dev/null
@@ -1,17 +0,0 @@
-# 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/.
-
-test_dirs := \
-  mach/mach/test \
-  mozbuild/mozbuild/test \
-  mozbuild/mozbuild/test/action \
-  mozbuild/mozbuild/test/backend \
-  mozbuild/mozbuild/test/controller \
-  mozbuild/mozbuild/test/compilation \
-  mozbuild/mozbuild/test/frontend \
-  mozbuild/mozpack/test \
-  mozbuild/dumbmake/test \
-  $(NULL)
-
-PYTHON_UNIT_TESTS := $(foreach dir,$(test_dirs),$(wildcard $(srcdir)/$(dir)/*.py))

--- a/python/moz.build
+++ b/python/moz.build
@@ -5,8 +5,65 @@
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 SPHINX_PYTHON_PACKAGE_DIRS += [
     'codegen',
     'mozbuild/mozbuild',
     'mozbuild/mozpack',
     'mozversioncontrol/mozversioncontrol',
 ]
+
+PYTHON_UNIT_TESTS += [
+    'mach/mach/test/__init__.py',
+    'mach/mach/test/common.py',
+    'mach/mach/test/test_conditions.py',
+    'mach/mach/test/test_config.py',
+    'mach/mach/test/test_entry_point.py',
+    'mach/mach/test/test_error_output.py',
+    'mach/mach/test/test_logger.py',
+    'mozbuild/dumbmake/test/__init__.py',
+    'mozbuild/dumbmake/test/test_dumbmake.py',
+    'mozbuild/mozbuild/test/__init__.py',
+    'mozbuild/mozbuild/test/action/test_buildlist.py',
+    'mozbuild/mozbuild/test/backend/__init__.py',
+    'mozbuild/mozbuild/test/backend/common.py',
+    'mozbuild/mozbuild/test/backend/test_android_eclipse.py',
+    'mozbuild/mozbuild/test/backend/test_configenvironment.py',
+    'mozbuild/mozbuild/test/backend/test_recursivemake.py',
+    'mozbuild/mozbuild/test/backend/test_visualstudio.py',
+    'mozbuild/mozbuild/test/common.py',
+    'mozbuild/mozbuild/test/compilation/__init__.py',
+    'mozbuild/mozbuild/test/compilation/test_warnings.py',
+    'mozbuild/mozbuild/test/controller/__init__.py',
+    'mozbuild/mozbuild/test/controller/test_clobber.py',
+    'mozbuild/mozbuild/test/frontend/__init__.py',
+    'mozbuild/mozbuild/test/frontend/test_emitter.py',
+    'mozbuild/mozbuild/test/frontend/test_namespaces.py',
+    'mozbuild/mozbuild/test/frontend/test_reader.py',
+    'mozbuild/mozbuild/test/frontend/test_sandbox.py',
+    'mozbuild/mozbuild/test/frontend/test_sandbox_symbols.py',
+    'mozbuild/mozbuild/test/test_base.py',
+    'mozbuild/mozbuild/test/test_containers.py',
+    'mozbuild/mozbuild/test/test_expression.py',
+    'mozbuild/mozbuild/test/test_jarmaker.py',
+    'mozbuild/mozbuild/test/test_line_endings.py',
+    'mozbuild/mozbuild/test/test_link_deps.py',
+    'mozbuild/mozbuild/test/test_makeutil.py',
+    'mozbuild/mozbuild/test/test_mozconfig.py',
+    'mozbuild/mozbuild/test/test_mozinfo.py',
+    'mozbuild/mozbuild/test/test_preprocessor.py',
+    'mozbuild/mozbuild/test/test_pythonutil.py',
+    'mozbuild/mozbuild/test/test_testing.py',
+    'mozbuild/mozbuild/test/test_util.py',
+    'mozbuild/mozpack/test/__init__.py',
+    'mozbuild/mozpack/test/test_chrome_flags.py',
+    'mozbuild/mozpack/test/test_chrome_manifest.py',
+    'mozbuild/mozpack/test/test_copier.py',
+    'mozbuild/mozpack/test/test_errors.py',
+    'mozbuild/mozpack/test/test_files.py',
+    'mozbuild/mozpack/test/test_manifests.py',
+    'mozbuild/mozpack/test/test_mozjar.py',
+    'mozbuild/mozpack/test/test_packager.py',
+    'mozbuild/mozpack/test/test_packager_formats.py',
+    'mozbuild/mozpack/test/test_packager_l10n.py',
+    'mozbuild/mozpack/test/test_path.py',
+    'mozbuild/mozpack/test/test_unify.py',
+]

--- a/python/mozbuild/mozbuild/frontend/emitter.py
+++ b/python/mozbuild/mozbuild/frontend/emitter.py
@@ -380,16 +380,17 @@ class TreeMetadataEmitter(LoggingMixin):
             'FILES_PER_UNIFIED_FILE',
             'USE_STATIC_LIBS',
             'GENERATED_FILES',
             'IS_GYP_DIR',
             'JS_MODULES_PATH',
             'MSVC_ENABLE_PGO',
             'NO_DIST_INSTALL',
             'OS_LIBS',
+            'PYTHON_UNIT_TESTS',
             'RCFILE',
             'RESFILE',
             'RCINCLUDE',
             'DEFFILE',
             'WIN32_EXE_LDFLAGS',
             'LD_VERSION_SCRIPT',
         ]
         for v in varlist:

--- a/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
+++ b/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
@@ -284,16 +284,20 @@ VARIABLES = {
         """A parallel version of ``DIRS``.
 
         Ideally this variable does not exist. It is provided so a transition
         from recursive makefiles can be made. Once the build system has been
         converted to not use Makefile's for the build frontend, this will
         likely go away.
         """, None),
 
+    'PYTHON_UNIT_TESTS': (StrictOrderingOnAppendList, list,
+        """A list of python unit tests.
+        """, None),
+
     'HOST_LIBRARY_NAME': (unicode, unicode,
         """Name of target library generated when cross compiling.
         """, 'binaries'),
 
     'JAVA_JAR_TARGETS': (dict, dict,
         """Defines Java JAR targets to be built.
 
         This variable should not be populated directly. Instead, it should

--- a/testing/mozbase/Makefile.in
+++ b/testing/mozbase/Makefile.in
@@ -1,16 +1,12 @@
 # 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/.
 
-PYTHON_UNIT_TESTS := \
-  test.py \
-  $(NULL)
-
 include $(topsrcdir)/config/rules.mk
 
 # Harness packages from the srcdir
 MOZBASE_PACKAGES = \
   manifestparser \
   mozcrash \
   mozfile \
   mozhttpd \

--- a/testing/mozbase/moz.build
+++ b/testing/mozbase/moz.build
@@ -1,6 +1,9 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # 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/.
 
+PYTHON_UNIT_TESTS += [
+    'test.py',
+]

--- a/testing/xpcshell/Makefile.in
+++ b/testing/xpcshell/Makefile.in
@@ -1,18 +1,13 @@
 #
 # 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/.
 
-# Run selftests
-PYTHON_UNIT_TESTS := \
-  selftest.py
-  $(NULL)
-
 include $(topsrcdir)/config/rules.mk
 
 # Harness files from the srcdir
 TEST_HARNESS_FILES := \
   runxpcshelltests.py \
   remotexpcshelltests.py \
   runtestsb2g.py \
   head.js \

--- a/testing/xpcshell/moz.build
+++ b/testing/xpcshell/moz.build
@@ -1,8 +1,11 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # 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/.
 
 TEST_DIRS += ['example']
 
+PYTHON_UNIT_TESTS += [
+    'selftest.py',
+]

--- a/xpcom/typelib/xpt/tools/Makefile.in
+++ b/xpcom/typelib/xpt/tools/Makefile.in
@@ -6,10 +6,8 @@
 INTERNAL_TOOLS	= 1
 
 XPT_TOOL_FILES := xpt.py
 # SDK_BIN_DIR is declared in config.mk, so this needs to be a deferred
 # assignment.
 XPT_TOOL_DEST = $(SDK_BIN_DIR)
 XPT_TOOL_TARGET := export
 INSTALL_TARGETS += XPT_TOOL
-
-PYTHON_UNIT_TESTS := runtests.py

--- a/xpcom/typelib/xpt/tools/moz.build
+++ b/xpcom/typelib/xpt/tools/moz.build
@@ -1,6 +1,9 @@
 # -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
 # vim: set filetype=python:
 # 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/.
 
+PYTHON_UNIT_TESTS += [
+    'runtests.py',
+]