diff --git a/CMakeLists.txt b/CMakeLists.txt
index 629f4c7..07f822c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -59,6 +59,8 @@ install(DIRECTORY cmake DESTINATION share/cartographer/)
 
 file(GLOB_RECURSE ALL_LIBRARY_HDRS "cartographer/*.h")
 file(GLOB_RECURSE ALL_LIBRARY_SRCS "cartographer/*.cc")
+file(GLOB_RECURSE TEST_LIBRARY_HDRS "cartographer/fake_*.h" "cartographer/*test_helpers*.h" "cartographer/mock_*.h")
+file(GLOB_RECURSE TEST_LIBRARY_SRCS "cartographer/fake_*.cc" "cartographer/*test_helpers*.cc" "cartographer/mock_*.cc")
 file(GLOB_RECURSE ALL_TESTS "cartographer/*_test.cc")
 file(GLOB_RECURSE ALL_EXECUTABLES "cartographer/*_main.cc")
 
@@ -67,24 +69,31 @@ file(GLOB_RECURSE ALL_DOTFILES ".*/*")
 if (ALL_DOTFILES)
   list(REMOVE_ITEM ALL_LIBRARY_HDRS ${ALL_DOTFILES})
   list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_DOTFILES})
+  list(REMOVE_ITEM TEST_LIBRARY_HDRS ${ALL_DOTFILES})
+  list(REMOVE_ITEM TEST_LIBRARY_SRCS ${ALL_DOTFILES})
   list(REMOVE_ITEM ALL_TESTS ${ALL_DOTFILES})
   list(REMOVE_ITEM ALL_EXECUTABLES ${ALL_DOTFILES})
 endif()
-
-list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_TESTS})
 list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_EXECUTABLES})
+list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_TESTS})
+list(REMOVE_ITEM ALL_LIBRARY_HDRS ${TEST_LIBRARY_HDRS})
+list(REMOVE_ITEM ALL_LIBRARY_SRCS ${TEST_LIBRARY_SRCS})
 file(GLOB_RECURSE ALL_GRPC_FILES "cartographer/cloud/*")
 file(GLOB_RECURSE ALL_PROMETHEUS_FILES "cartographer/cloud/metrics/prometheus/*")
 list(REMOVE_ITEM ALL_GRPC_FILES ${ALL_PROMETHEUS_FILES})
 if (NOT ${BUILD_GRPC})
   list(REMOVE_ITEM ALL_LIBRARY_HDRS ${ALL_GRPC_FILES})
   list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_GRPC_FILES})
+  list(REMOVE_ITEM TEST_LIBRARY_HDRS ${ALL_GRPC_FILES})
+  list(REMOVE_ITEM TEST_LIBRARY_SRCS ${ALL_GRPC_FILES})
   list(REMOVE_ITEM ALL_TESTS ${ALL_GRPC_FILES})
   list(REMOVE_ITEM ALL_EXECUTABLES ${ALL_GRPC_FILES})
 endif()
 if (NOT ${BUILD_PROMETHEUS})
   list(REMOVE_ITEM ALL_LIBRARY_HDRS ${ALL_PROMETHEUS_FILES})
   list(REMOVE_ITEM ALL_LIBRARY_SRCS ${ALL_PROMETHEUS_FILES})
+  list(REMOVE_ITEM TEST_LIBRARY_HDRS ${ALL_PROMETHEUS_FILES})
+  list(REMOVE_ITEM TEST_LIBRARY_SRCS ${ALL_PROMETHEUS_FILES})
   list(REMOVE_ITEM ALL_TESTS ${ALL_PROMETHEUS_FILES})
   list(REMOVE_ITEM ALL_EXECUTABLES ${ALL_PROMETHEUS_FILES})
 endif()
@@ -182,22 +191,6 @@ if(${BUILD_GRPC})
   endif()
 endif()
 
-foreach(ABS_FIL ${ALL_TESTS})
-  file(RELATIVE_PATH REL_FIL ${PROJECT_SOURCE_DIR} ${ABS_FIL})
-  get_filename_component(DIR ${REL_FIL} DIRECTORY)
-  get_filename_component(FIL_WE ${REL_FIL} NAME_WE)
-  # Replace slashes as required for CMP0037.
-  string(REPLACE "/" "." TEST_TARGET_NAME "${DIR}/${FIL_WE}")
-  google_test("${TEST_TARGET_NAME}" ${ABS_FIL})
-  if(${BUILD_GRPC})
-    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC grpc++)
-    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC async_grpc)
-  endif()
-  if(${BUILD_PROMETHEUS})
-    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC prometheus-cpp)
-  endif()
-endforeach()
-
 target_include_directories(${PROJECT_NAME} SYSTEM PUBLIC
   "${EIGEN3_INCLUDE_DIR}")
 target_link_libraries(${PROJECT_NAME} PUBLIC ${EIGEN3_LIBRARIES})
@@ -236,6 +229,38 @@ if(${BUILD_PROMETHEUS})
   target_compile_definitions(${PROJECT_NAME} PUBLIC USE_PROMETHEUS=1)
 endif()
 
+set(TARGET_COMPILE_FLAGS "${TARGET_COMPILE_FLAGS} ${GOOG_CXX_FLAGS}")
+set_target_properties(${PROJECT_NAME} PROPERTIES
+  COMPILE_FLAGS ${TARGET_COMPILE_FLAGS})
+
+set(TEST_LIB
+  cartographer_test_library
+)
+add_library(${TEST_LIB} ${TEST_LIBRARY_HDRS} ${TEST_LIBRARY_SRCS})
+target_include_directories(${TEST_LIB} SYSTEM PRIVATE
+  "${GMOCK_INCLUDE_DIRS}")
+target_link_libraries(${TEST_LIB} PUBLIC ${GMOCK_LIBRARY})
+target_link_libraries(${TEST_LIB} PUBLIC ${PROJECT_NAME})
+set_target_properties(${TEST_LIB} PROPERTIES
+  COMPILE_FLAGS ${TARGET_COMPILE_FLAGS})
+
+foreach(ABS_FIL ${ALL_TESTS})
+  file(RELATIVE_PATH REL_FIL ${PROJECT_SOURCE_DIR} ${ABS_FIL})
+  get_filename_component(DIR ${REL_FIL} DIRECTORY)
+  get_filename_component(FIL_WE ${REL_FIL} NAME_WE)
+  # Replace slashes as required for CMP0037.
+  string(REPLACE "/" "." TEST_TARGET_NAME "${DIR}/${FIL_WE}")
+  google_test("${TEST_TARGET_NAME}" ${ABS_FIL})
+  if(${BUILD_GRPC})
+    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC grpc++)
+    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC async_grpc)
+  endif()
+  if(${BUILD_PROMETHEUS})
+    target_link_libraries("${TEST_TARGET_NAME}" PUBLIC prometheus-cpp)
+  endif()
+  target_link_libraries("${TEST_TARGET_NAME}" PUBLIC ${TEST_LIB})
+endforeach()
+
 # Add the binary directory first, so that port.h is included after it has
 # been generated.
 target_include_directories(${PROJECT_NAME} PUBLIC
@@ -244,15 +269,6 @@ target_include_directories(${PROJECT_NAME} PUBLIC
     $<INSTALL_INTERFACE:include>
 )
 
-# TODO(damonkohler): Create a testing library.
-target_include_directories(${PROJECT_NAME} SYSTEM PRIVATE
-  "${GMOCK_INCLUDE_DIRS}")
-target_link_libraries(${PROJECT_NAME} PUBLIC ${GMOCK_LIBRARY})
-
-set(TARGET_COMPILE_FLAGS "${TARGET_COMPILE_FLAGS} ${GOOG_CXX_FLAGS}")
-set_target_properties(${PROJECT_NAME} PROPERTIES
-  COMPILE_FLAGS ${TARGET_COMPILE_FLAGS})
-
 install(
   TARGETS ${PROJECT_NAME}
   EXPORT CartographerExport