diff --git a/CMakeLists.txt b/CMakeLists.txt
index 366925e..049b6fe 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -3,15 +3,18 @@ cmake_minimum_required(VERSION 3.5)
 project(mtl LANGUAGES CXX C ASM)
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
+option(BUILD_TESTS "Build tests" ON)
+
 message("Compiling MTL for ${CMAKE_SYSTEM_PROCESSOR}")
 
 # CONFIGURE_DEPENDS option was added in CMake v3.12. This option allows the
 # build system to automatically re-run CMake if the glob changes, solving the
 # major issue with globbing. May have a performance impact, but it should be
 # negligible compared to the time spent building.
-file(GLOB mtl_sources_common LIST_DIRECTORIES false CONFIGURE_DEPENDS src/*.cpp src/*.c src/*.s src/tests/*.cpp)
+file(GLOB mtl_sources_common LIST_DIRECTORIES false CONFIGURE_DEPENDS src/common/*.cpp src/common/*.c src/common/*.s)
 file(GLOB mtl_sources_armv4t LIST_DIRECTORIES false CONFIGURE_DEPENDS src/armv4t/*.cpp src/armv4t/*.c src/armv4t/*.s)
 file(GLOB mtl_sources_gba LIST_DIRECTORIES false CONFIGURE_DEPENDS src/gba/*.cpp src/gba/*.c src/gba/*.s)
+file(GLOB mtl_sources_test LIST_DIRECTORIES false CONFIGURE_DEPENDS src/tests/*.cpp)
 
 set(mtl_include_common "include")
 set(mtl_include_gba "include/gba")
@@ -39,6 +42,12 @@ if (CMAKE_SYSTEM_PROCESSOR STREQUAL "armv4t")
 	target_link_libraries(${PROJECT_NAME} PUBLIC ${PROJECT_NAME}_armv4t)
 endif()
 
+if (BUILD_TESTS STREQUAL "ON")
+	add_library(${PROJECT_NAME}_test OBJECT)
+	target_sources(${PROJECT_NAME}_test PRIVATE "${mtl_sources_test}")
+	target_link_libraries(${PROJECT_NAME} PUBLIC ${PROJECT_NAME}_test)
+endif()
+
 target_sources(${PROJECT_NAME}_common PRIVATE "${mtl_sources_common}")
 target_include_directories(${PROJECT_NAME}_common PUBLIC "${mtl_include_common}")
 target_link_libraries(${PROJECT_NAME} PUBLIC ${PROJECT_NAME}_common)
diff --git a/src/mat.cpp b/include/mtl/mat_impl.hpp
similarity index 79%
rename from src/mat.cpp
rename to include/mtl/mat_impl.hpp
index 2a6c1f2..53df001 100644
--- a/src/mat.cpp
+++ b/include/mtl/mat_impl.hpp
@@ -1,3 +1,8 @@
+/*
+ * This file should only be included by files that explicitly instantiate
+ * matrix classes.
+ */
+#pragma once
 #pragma GCC push_options
 #pragma GCC optimize("unroll-loops")
 
@@ -125,23 +130,6 @@ mat<4, 4> mat<4, 4>::translation(const vec<D - 1>& v) {
 	return r;
 }
 
-template class mat<2, 2>;
-template class mat<3, 3>;
-template class mat<4, 4>;
-template class mat<1, 2>;
-template class mat<1, 3>;
-template class mat<1, 4>;
-
-template mat<2, 2> operator*(const vec<2>&, const mat<1, 2>&);
-template mat<3, 3> operator*(const vec<3>&, const mat<1, 3>&);
-template mat<4, 4> operator*(const vec<4>&, const mat<1, 4>&);
-
-template mat<4, 4> mat<4, 4>::operator*(const mat<4, 4>&) const;
-template mat<3, 3> mat<3, 3>::operator*(const mat<3, 3>&) const;
-template mat<2, 2> mat<2, 2>::operator*(const mat<2, 2>&) const;
-
-template mat<4, 4> mat<4, 4>::translation<4, true>(const vec<3>&);
-
 } // namespace mtl
 
 #pragma GCC pop_options
diff --git a/src/log.cpp b/src/common/log.cpp
similarity index 100%
rename from src/log.cpp
rename to src/common/log.cpp
diff --git a/src/common/mat_1x2.cpp b/src/common/mat_1x2.cpp
new file mode 100644
index 0000000..99c47e6
--- /dev/null
+++ b/src/common/mat_1x2.cpp
@@ -0,0 +1,8 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<1, 2>;
+
+}
+
diff --git a/src/common/mat_1x3.cpp b/src/common/mat_1x3.cpp
new file mode 100644
index 0000000..fdfd43a
--- /dev/null
+++ b/src/common/mat_1x3.cpp
@@ -0,0 +1,8 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<1, 3>;
+
+}
+
diff --git a/src/common/mat_1x4.cpp b/src/common/mat_1x4.cpp
new file mode 100644
index 0000000..a9a5c5e
--- /dev/null
+++ b/src/common/mat_1x4.cpp
@@ -0,0 +1,8 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<1, 4>;
+
+}
+
diff --git a/src/common/mat_2x2.cpp b/src/common/mat_2x2.cpp
new file mode 100644
index 0000000..1592fde
--- /dev/null
+++ b/src/common/mat_2x2.cpp
@@ -0,0 +1,11 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<2, 2>;
+
+template mat<2, 2> operator*(const vec<2>&, const mat<1, 2>&);
+template mat<2, 2> mat<2, 2>::operator*(const mat<2, 2>&) const;
+
+}
+
diff --git a/src/common/mat_3x3.cpp b/src/common/mat_3x3.cpp
new file mode 100644
index 0000000..a08a43c
--- /dev/null
+++ b/src/common/mat_3x3.cpp
@@ -0,0 +1,11 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<3, 3>;
+
+template mat<3, 3> operator*(const vec<3>&, const mat<1, 3>&);
+template mat<3, 3> mat<3, 3>::operator*(const mat<3, 3>&) const;
+
+}
+
diff --git a/src/common/mat_4x4.cpp b/src/common/mat_4x4.cpp
new file mode 100644
index 0000000..cb7fd42
--- /dev/null
+++ b/src/common/mat_4x4.cpp
@@ -0,0 +1,12 @@
+#include "mtl/mat_impl.hpp"
+
+namespace mtl {
+
+template class mat<4, 4>;
+
+template mat<4, 4> operator*(const vec<4>&, const mat<1, 4>&);
+template mat<4, 4> mat<4, 4>::operator*(const mat<4, 4>&) const;
+
+template mat<4, 4> mat<4, 4>::translation<4, true>(const vec<3>&);
+
+}
diff --git a/src/string.cpp b/src/common/string.cpp
similarity index 99%
rename from src/string.cpp
rename to src/common/string.cpp
index dfe9a2a..c90697f 100644
--- a/src/string.cpp
+++ b/src/common/string.cpp
@@ -2,6 +2,7 @@
 
 #include <cstddef>
 #include <cstring>
+#include <algorithm>
 
 #include "mtl/utility.hpp"
 #include "mtl/string_view.hpp"
diff --git a/src/string_view.cpp b/src/common/string_view.cpp
similarity index 100%
rename from src/string_view.cpp
rename to src/common/string_view.cpp