diff --git a/src/include/rules.h b/src/include/rules.h
index 6ebb37e804..ec3d22d7d1 100644
--- a/src/include/rules.h
+++ b/src/include/rules.h
@@ -3,6 +3,12 @@
 #ifndef _RULES_H
 #define _RULES_H
 
+#if defined(__TEST__)
+#define ENV_TEST 1
+#else
+#define ENV_TEST 0
+#endif
+
 #if defined(__TIMELESS__)
 #define ENV_TIMELESS 1
 #else
diff --git a/tests/Makefile.inc b/tests/Makefile.inc
index ca974a905a..027091c5e6 100644
--- a/tests/Makefile.inc
+++ b/tests/Makefile.inc
@@ -39,6 +39,8 @@ TEST_CFLAGS += -I$(dir $(TEST_KCONFIG_AUTOHEADER))
 
 TEST_CFLAGS += -std=gnu11 -Os -ffunction-sections -fdata-sections -fno-builtin
 
+TEST_CFLAGS += -D__TEST__
+
 # Checkout Cmocka repository
 forgetthis:=$(shell git submodule update --init --checkout 3rdparty/cmocka)