diff --git a/browser/Makefile.in b/browser/Makefile.in
index 8b7dc07b28da..2eb9e708f68e 100644
--- a/browser/Makefile.in
+++ b/browser/Makefile.in
@@ -14,6 +14,3 @@ ifdef MOZ_MAINTENANCE_SERVICE
 	$(MAKE) -C installer/windows maintenanceservice_installer
 endif
 endif
-
-check::
-	$(PYTHON) $(topsrcdir)/build/compare-mozconfig/compare-mozconfigs-wrapper.py
diff --git a/build/moz.build b/build/moz.build
index 412df22299de..9a399ca7404b 100644
--- a/build/moz.build
+++ b/build/moz.build
@@ -44,3 +44,7 @@ for var in ('MOZ_CRASHREPORTER', 'MOZ_PROFILE_MIGRATOR',
     if CONFIG[var]:
         DEFINES[var] = True
 
+if CONFIG['MOZ_BUILD_APP'] == 'browser':
+    PYTHON_UNIT_TESTS += [
+        'compare-mozconfig/compare-mozconfigs-wrapper.py',
+    ]
diff --git a/config/Makefile.in b/config/Makefile.in
index c593a7d586e8..a42055eeeba0 100644
--- a/config/Makefile.in
+++ b/config/Makefile.in
@@ -39,8 +39,6 @@ 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
diff --git a/config/config.mk b/config/config.mk
index 3e8edf43ba68..6ef47ab37007 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -65,6 +65,7 @@ _MOZBUILD_EXTERNAL_VARIABLES := \
   NO_DIST_INSTALL \
   PARALLEL_DIRS \
   PROGRAM \
+  PYTHON_UNIT_TESTS \
   RESOURCE_FILES \
   SDK_HEADERS \
   SDK_LIBRARY \
diff --git a/config/moz.build b/config/moz.build
index 04dd19e5c5fb..d355cb5e79e2 100644
--- a/config/moz.build
+++ b/config/moz.build
@@ -28,3 +28,10 @@ if CONFIG['GKMEDIAS_SHARED_LIBRARY']:
 
 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',
+]
diff --git a/dom/bindings/Makefile.in b/dom/bindings/Makefile.in
index 12d5d4affa10..0a728f9f3669 100644
--- a/dom/bindings/Makefile.in
+++ b/dom/bindings/Makefile.in
@@ -24,8 +24,6 @@ CPPSRCS += $(globalgen_sources) $(unified_binding_cpp_files)
 # Bug 932092 tracks.
 LOCAL_INCLUDES += -I$(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
diff --git a/dom/bindings/moz.build b/dom/bindings/moz.build
index 3a286f079eea..874903c977ad 100644
--- a/dom/bindings/moz.build
+++ b/dom/bindings/moz.build
@@ -96,3 +96,7 @@ 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',
+]
diff --git a/python/Makefile.in b/python/Makefile.in
deleted file mode 100644
index 1ac2776e46a9..000000000000
--- 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))
diff --git a/python/moz.build b/python/moz.build
index a55d55e9568f..72b21bea6cd1 100644
--- a/python/moz.build
+++ b/python/moz.build
@@ -10,3 +10,60 @@ SPHINX_PYTHON_PACKAGE_DIRS += [
     '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',
+]
diff --git a/python/mozbuild/mozbuild/frontend/emitter.py b/python/mozbuild/mozbuild/frontend/emitter.py
index cf410c95627f..8d83cfddedb6 100644
--- a/python/mozbuild/mozbuild/frontend/emitter.py
+++ b/python/mozbuild/mozbuild/frontend/emitter.py
@@ -385,6 +385,7 @@ class TreeMetadataEmitter(LoggingMixin):
             'MSVC_ENABLE_PGO',
             'NO_DIST_INSTALL',
             'OS_LIBS',
+            'PYTHON_UNIT_TESTS',
             'RCFILE',
             'RESFILE',
             'RCINCLUDE',
diff --git a/python/mozbuild/mozbuild/frontend/sandbox_symbols.py b/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
index 94706dba174e..a2457e80fd40 100644
--- a/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
+++ b/python/mozbuild/mozbuild/frontend/sandbox_symbols.py
@@ -289,6 +289,10 @@ VARIABLES = {
         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'),
diff --git a/testing/mozbase/Makefile.in b/testing/mozbase/Makefile.in
index 7d12e0139870..db25ca1a7194 100644
--- a/testing/mozbase/Makefile.in
+++ b/testing/mozbase/Makefile.in
@@ -2,10 +2,6 @@
 # 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
diff --git a/testing/mozbase/moz.build b/testing/mozbase/moz.build
index 895d11993cfb..34d90e79cef5 100644
--- a/testing/mozbase/moz.build
+++ b/testing/mozbase/moz.build
@@ -4,3 +4,6 @@
 # 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',
+]
diff --git a/testing/xpcshell/Makefile.in b/testing/xpcshell/Makefile.in
index 081eb21f8777..4d11c1daa9d5 100644
--- a/testing/xpcshell/Makefile.in
+++ b/testing/xpcshell/Makefile.in
@@ -3,11 +3,6 @@
 # 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
diff --git a/testing/xpcshell/moz.build b/testing/xpcshell/moz.build
index d63be6e8d971..aeaedbc4dd45 100644
--- a/testing/xpcshell/moz.build
+++ b/testing/xpcshell/moz.build
@@ -6,3 +6,6 @@
 
 TEST_DIRS += ['example']
 
+PYTHON_UNIT_TESTS += [
+    'selftest.py',
+]
diff --git a/xpcom/typelib/xpt/tools/Makefile.in b/xpcom/typelib/xpt/tools/Makefile.in
index fe12f952c3a4..e7cacf3dc6a1 100644
--- a/xpcom/typelib/xpt/tools/Makefile.in
+++ b/xpcom/typelib/xpt/tools/Makefile.in
@@ -11,5 +11,3 @@ XPT_TOOL_FILES := xpt.py
 XPT_TOOL_DEST = $(SDK_BIN_DIR)
 XPT_TOOL_TARGET := export
 INSTALL_TARGETS += XPT_TOOL
-
-PYTHON_UNIT_TESTS := runtests.py
diff --git a/xpcom/typelib/xpt/tools/moz.build b/xpcom/typelib/xpt/tools/moz.build
index 895d11993cfb..0905d78f5894 100644
--- a/xpcom/typelib/xpt/tools/moz.build
+++ b/xpcom/typelib/xpt/tools/moz.build
@@ -4,3 +4,6 @@
 # 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',
+]