diff --git a/testing/Makefile b/testing/Makefile
index fffb10d9..f7719680 100644
--- a/testing/Makefile
+++ b/testing/Makefile
@@ -1,4 +1,4 @@
-COMMON_LIB_DIR?=${PWD}/lib
+LIB_DIR?=${PWD}/lib
 TEST_DIRS=$(shell dirname $(wildcard */Makefile))
 
 DIRS=googletest hello-simulator kaleidoscope common issue_840
@@ -7,7 +7,7 @@ CLEANDIRS = $(DIRS:%=clean-%)
 .PHONY: subdirs $(CLEANDIRS)
 
 clean: googletest/Makefile $(CLEANDIRS)
-	rm -rf "$(COMMON_LIB_DIR)"
+	rm -rf "$(LIB_DIR)"
 
 $(CLEANDIRS): 
 	cd $(@:clean-%=%) && $(MAKE) clean
@@ -22,7 +22,7 @@ googletest/Makefile:
 	cd googletest && cmake .
 
 common: 
-	cd common && COMMON_LIB_DIR="${COMMON_LIB_DIR}" $(MAKE)
+	cd common && LIB_DIR="${LIB_DIR}" $(MAKE)
 
 hello-simulator:
 	@:
diff --git a/testing/common/fix-macros.h b/testing/common/fix-macros.h
index 4ca9bd22..0ba58308 100644
--- a/testing/common/fix-macros.h
+++ b/testing/common/fix-macros.h
@@ -14,21 +14,13 @@
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#pragma once
+// No `#pragma once` since these undefs need to have every time a Kaleidoscope/
+// Arduino header is included before non-Kaleidoscope/Arduino header.
+// #pragma once
 
-#include "Kaleidoscope.h"
 
 #undef min
 #undef max
 #undef T
 #undef U
 #undef TEST
-
-#define SETUP_GOOGLETEST() \
-  void executeTestFunction() { \
-    setup(); /* setup Kaleidoscope */ \
-    /* Turn off virtual_io's input. */ \
-    Kaleidoscope.device().keyScanner().setEnableReadMatrix(false); \
-    testing::InitGoogleTest(); \
-    RUN_ALL_TESTS(); \
-  }
diff --git a/testing/common/setup-googletest.h b/testing/common/setup-googletest.h
new file mode 100644
index 00000000..753cc863
--- /dev/null
+++ b/testing/common/setup-googletest.h
@@ -0,0 +1,40 @@
+/* -*- mode: c++ -*-
+ * Copyright (C) 2020  Eric Paniagua (epaniagua@google.com)
+ *
+ * This program is free software: you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+// NOTE: This should always be the last header file included in test source files.
+
+#pragma once
+
+#include "kaleidoscope/key_defs_keyboard.h"
+#include "Kaleidoscope.h"
+
+// Out of order because `fix-macros.h` clears the preprocessor environment for
+// gtest and gmock.
+#include "testing/common/fix-macros.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+#include "testing/common/matchers.h"
+#include "testing/common/VirtualDeviceTest.h"
+
+#define SETUP_GOOGLETEST() \
+  void executeTestFunction() { \
+    setup(); /* setup Kaleidoscope */ \
+    /* Turn off virtual_io's input. */ \
+    Kaleidoscope.device().keyScanner().setEnableReadMatrix(false); \
+    testing::InitGoogleTest(); \
+    RUN_ALL_TESTS(); \
+  }
diff --git a/testing/issue_840/test/simulator_test.cpp b/testing/issue_840/test/simulator_test.cpp
index 321c1cc1..a4dd8c31 100644
--- a/testing/issue_840/test/simulator_test.cpp
+++ b/testing/issue_840/test/simulator_test.cpp
@@ -14,18 +14,7 @@
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "kaleidoscope/key_defs_keyboard.h"
-
-// Out of order because `fix-macros.h` clears the preprocessor environment for
-// gtest and gmock.
-#include "testing/common/fix-macros.h"
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-
-#include <iostream>
-
-#include "testing/common/matchers.h"
-#include "testing/common/VirtualDeviceTest.h"
+#include "testing/common/setup-googletest.h"
 
 SETUP_GOOGLETEST();
 
diff --git a/testing/kaleidoscope/test/simulator_test.cpp b/testing/kaleidoscope/test/simulator_test.cpp
index 95e8774a..ebef4c07 100644
--- a/testing/kaleidoscope/test/simulator_test.cpp
+++ b/testing/kaleidoscope/test/simulator_test.cpp
@@ -14,18 +14,7 @@
  * this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#include "kaleidoscope/key_defs_keyboard.h"
-
-// Out of order because `fix-macros.h` clears the preprocessor environment for
-// gtest and gmock.
-#include "testing/common/fix-macros.h"
-#include "gmock/gmock.h"
-#include "gtest/gtest.h"
-
-#include <iostream>
-
-#include "testing/common/matchers.h"
-#include "testing/common/VirtualDeviceTest.h"
+#include "testing/common/setup-googletest.h"
 
 SETUP_GOOGLETEST();