diff --git a/.gitignore b/.gitignore
index e48918d32..bb3817ba5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -128,10 +128,13 @@
 /src/common/Makefile.in
 /src/common/common_sha1.i
 /src/common/libor.a
+/src/common/libor-testing.a
 /src/common/libor.lib
 /src/common/libor-crypto.a
+/src/common/libor-crypto-testing.a
 /src/common/libor-crypto.lib
 /src/common/libor-event.a
+/src/common/libor-event-testing.a
 /src/common/libor-event.lib
 /src/common/libcurve25519_donna.a
 /src/common/libcurve25519_donna.lib
@@ -150,6 +153,7 @@
 /src/or/tor
 /src/or/tor.exe
 /src/or/libtor.a
+/src/or/libtor-testing.a
 /src/or/libtor.lib
 
 # /src/test
diff --git a/changes/fancy_testing b/changes/fancy_testing
new file mode 100644
index 000000000..4d971943b
--- /dev/null
+++ b/changes/fancy_testing
@@ -0,0 +1,9 @@
+  o Build features:
+
+    - Tor now builds each source file in two modes: a mode that avoids
+      exposing identifiers needlessly, and another mode that exposes
+      more identifiers for testing. This lets the compiler do better at
+      optimizing the production code, while enabling us to take more
+      radical measures to let the unit tests test things.
+
+
diff --git a/configure.ac b/configure.ac
index 235f19b43..34ed524dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -39,6 +39,10 @@ AC_ARG_ENABLE(static-tor,
    AS_HELP_STRING(--enable-static-tor, Create an entirely static Tor binary. Requires --with-openssl-dir and --with-libevent-dir and --with-zlib-dir))
 AC_ARG_ENABLE(curve25519,
    AS_HELP_STRING(--disable-curve25519, Build Tor with no curve25519 elliptic-curve crypto support))
+AC_ARG_ENABLE(unittests,
+   AS_HELP_STRING(--disable-unittests, [Don't build unit tests for Tor. Risky!]))
+
+AM_CONDITIONAL(UNITTESTS_ENABLED, test x$unittests != xno)
 
 if test "$enable_static_tor" = "yes"; then
   enable_static_libevent="yes";
diff --git a/src/common/include.am b/src/common/include.am
index 68275cbcf..3d8cc8e9e 100644
--- a/src/common/include.am
+++ b/src/common/include.am
@@ -1,5 +1,15 @@
 
-noinst_LIBRARIES+= src/common/libor.a src/common/libor-crypto.a src/common/libor-event.a
+noinst_LIBRARIES += \
+	src/common/libor.a \
+	src/common/libor-crypto.a \
+	src/common/libor-event.a
+
+if UNITTESTS_ENABLED
+noinst_LIBRARIES += \
+	src/common/libor-testing.a \
+	src/common/libor-crypto-testing.a \
+	src/common/libor-event-testing.a
+endif
 
 EXTRA_DIST+= \
   src/common/common_sha1.i	\
@@ -38,7 +48,7 @@ if CURVE25519_ENABLED
 libcrypto_extra_source=src/common/crypto_curve25519.c
 endif
 
-src_common_libor_a_SOURCES = \
+LIBOR_A_SOURCES = \
   src/common/address.c					\
   src/common/compat.c					\
   src/common/container.c				\
@@ -51,7 +61,7 @@ src_common_libor_a_SOURCES = \
   src/common/util_codedigest.c				\
   $(libor_extra_source)
 
-src_common_libor_crypto_a_SOURCES = \
+LIBOR_CRYPTO_A_SOURCES = \
   src/common/aes.c		\
   src/common/crypto.c		\
   src/common/crypto_format.c	\
@@ -59,7 +69,19 @@ src_common_libor_crypto_a_SOURCES = \
   src/common/tortls.c		\
   $(libcrypto_extra_source)
 
-src_common_libor_event_a_SOURCES = src/common/compat_libevent.c
+LIBOR_EVENT_A_SOURCES = src/common/compat_libevent.c
+
+src_common_libor_a_SOURCES = $(LIBOR_A_SOURCES)
+src_common_libor_crypto_a_SOURCES = $(LIBOR_CRYPTO_A_SOURCES)
+src_common_libor_event_a_SOURCES = $(LIBOR_EVENT_A_SOURCES)
+
+src_common_libor_testing_a_SOURCES = $(LIBOR_A_SOURCES)
+src_common_libor_crypto_testing_a_SOURCES = $(LIBOR_CRYPTO_A_SOURCES)
+src_common_libor_event_testing_a_SOURCES = $(LIBOR_EVENT_A_SOURCES)
+
+src_common_libor_testing_a_CPPFLAGS = -DTOR_UNIT_TESTS $(AM_CPPFLAGS)
+src_common_libor_crypto_testing_a_CPPFLAGS = -DTOR_UNIT_TESTS $(AM_CPPFLAGS)
+src_common_libor_event_testing_a_CPPFLAGS = -DTOR_UNIT_TESTS $(AM_CPPFLAGS)
 
 COMMONHEADERS = \
   src/common/address.h				\
@@ -74,6 +96,7 @@ COMMONHEADERS = \
   src/common/memarea.h				\
   src/common/mempool.h				\
   src/common/procmon.h				\
+  src/common/testsupport.h			\
   src/common/torgzip.h				\
   src/common/torint.h				\
   src/common/torlog.h				\
diff --git a/src/common/testsupport.h b/src/common/testsupport.h
new file mode 100644
index 000000000..621fd8c83
--- /dev/null
+++ b/src/common/testsupport.h
@@ -0,0 +1,14 @@
+/* Copyright (c) 2013, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_TESTSUPPORT_H
+#define TOR_TESTSUPPORT_H
+
+#ifdef TOR_UNIT_TESTS
+#define STATIC_UNLESS_TESTING
+#else
+#define STATIC_UNLESS_TESTING static
+#endif
+
+#endif
+
diff --git a/src/or/include.am b/src/or/include.am
index 65dbeff53..91b9bfce7 100644
--- a/src/or/include.am
+++ b/src/or/include.am
@@ -1,5 +1,10 @@
 bin_PROGRAMS+= src/or/tor
-noinst_LIBRARIES+= src/or/libtor.a
+noinst_LIBRARIES += \
+	src/or/libtor.a
+if UNITTESTS_ENABLED
+noinst_LIBRARIES += \
+	src/or/libtor-testing.a
+endif
 
 if BUILD_NT_SERVICES
 tor_platform_source=src/or/ntmain.c
@@ -21,7 +26,7 @@ else
 onion_ntor_source=
 endif
 
-src_or_libtor_a_SOURCES = \
+LIBTOR_A_SOURCES = \
 	src/or/addressmap.c				\
 	src/or/buffers.c				\
 	src/or/channel.c				\
@@ -77,6 +82,9 @@ src_or_libtor_a_SOURCES = \
 	$(onion_ntor_source)				\
 	src/or/config_codedigest.c
 
+src_or_libtor_a_SOURCES = $(LIBTOR_A_SOURCES)
+src_or_libtor_testing_a_SOURCES = $(LIBTOR_A_SOURCES)
+
 #libtor_a_LIBADD = ../common/libor.a ../common/libor-crypto.a \
 #	../common/libor-event.a
 
@@ -90,6 +98,8 @@ AM_CPPFLAGS += -DSHARE_DATADIR="\"$(datadir)\"" \
         -DLOCALSTATEDIR="\"$(localstatedir)\"" \
         -DBINDIR="\"$(bindir)\""
 
+src_or_libtor_testing_a_CPPFLAGS = -DTOR_UNIT_TESTS $(AM_CPPFLAGS)
+
 # -L flags need to go in LDFLAGS. -l flags need to go in LDADD.
 # This seems to matter nowhere but on windows, but I assure you that it
 # matters a lot there, and is quite hard to debug if you forget to do it.
diff --git a/src/test/include.am b/src/test/include.am
index 112d1a79d..08eb7fba6 100644
--- a/src/test/include.am
+++ b/src/test/include.am
@@ -1,11 +1,15 @@
 TESTS+= src/test/test
 
-noinst_PROGRAMS+= src/test/test src/test/test-child src/test/bench
+noinst_PROGRAMS+= src/test/bench
+if UNITTESTS_ENABLED
+noinst_PROGRAMS+= src/test/test src/test/test-child
+endif
 
 src_test_AM_CPPFLAGS = -DSHARE_DATADIR="\"$(datadir)\"" \
         -DLOCALSTATEDIR="\"$(localstatedir)\"" \
         -DBINDIR="\"$(bindir)\""	       \
-	-I"$(top_srcdir)/src/or" -I"$(top_srcdir)/src/ext"
+	-I"$(top_srcdir)/src/or" -I"$(top_srcdir)/src/ext" \
+	-DTOR_UNIT_TESTS
 
 # -L flags need to go in LDFLAGS. -l flags need to go in LDADD.
 # This seems to matter nowhere but on Windows, but I assure you that it
@@ -36,9 +40,9 @@ src_test_bench_CPPFLAGS= $(src_test_AM_CPPFLAGS)
 
 src_test_test_LDFLAGS = @TOR_LDFLAGS_zlib@ @TOR_LDFLAGS_openssl@ \
         @TOR_LDFLAGS_libevent@
-src_test_test_LDADD = src/or/libtor.a src/common/libor.a \
-	src/common/libor-crypto.a $(LIBDONNA) \
-	src/common/libor-event.a \
+src_test_test_LDADD = src/or/libtor-testing.a src/common/libor-testing.a \
+	src/common/libor-crypto-testing.a $(LIBDONNA) \
+	src/common/libor-event-testing.a \
 	@TOR_ZLIB_LIBS@ @TOR_LIB_MATH@ @TOR_LIBEVENT_LIBS@ \
 	@TOR_OPENSSL_LIBS@ @TOR_LIB_WS32@ @TOR_LIB_GDI@ @CURVE25519_LIBS@