diff --git a/CMakeLists.txt b/CMakeLists.txt
index 794d45c..2ff8274 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2,7 +2,8 @@ cmake_minimum_required(VERSION 3.15.0)
 
 project(LocalSearchSolver LANGUAGES CXX)
 
-# Options.
+# Build options.
+option(LOCALSEARCHSOLVER_BUILD_TEST "Build unit tests" ON)
 option(LOCALSEARCHSOLVER_BUILD_EXAMPLES "Build examples" ON)
 
 # Avoid FetchContent warning.
@@ -17,7 +18,9 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 # Add sub-directories.
 add_subdirectory(extern)
 add_subdirectory(src)
-add_subdirectory(test)
+if(LOCALSEARCHSOLVER_BUILD_TEST)
+    add_subdirectory(test)
+endif()
 if(LOCALSEARCHSOLVER_BUILD_EXAMPLES)
     add_subdirectory(examples)
 endif()
diff --git a/extern/CMakeLists.txt b/extern/CMakeLists.txt
index 30010b4..808129f 100644
--- a/extern/CMakeLists.txt
+++ b/extern/CMakeLists.txt
@@ -1,10 +1,22 @@
 # Enable FetchContent.
 include(FetchContent)
 
-# Fetch fontanf/orproblems.
+# Fetch fontanf/optimizationtools.
+set(OPTIMIZATIONTOOLS_BUILD_TEST OFF)
 FetchContent_Declare(
-    orproblems
-    GIT_REPOSITORY https://github.com/fontanf/orproblems.git
-    GIT_TAG ba099d6bd0ac186e4113fe340789a1800fa72852)
-    #SOURCE_DIR "${PROJECT_SOURCE_DIR}/../orproblems/")
-FetchContent_MakeAvailable(orproblems)
+    optimizationtools
+    GIT_REPOSITORY https://github.com/fontanf/optimizationtools.git
+    GIT_TAG e8c379203792fcad764cce239986b325619475fd
+    #SOURCE_DIR "${PROJECT_SOURCE_DIR}/../optimizationtools/"
+    EXCLUDE_FROM_ALL)
+FetchContent_MakeAvailable(optimizationtools)
+
+# Fetch fontanf/orproblems.
+if(LOCALSEARCHSOLVER_BUILD_EXAMPLES)
+    FetchContent_Declare(
+        orproblems
+        GIT_REPOSITORY https://github.com/fontanf/orproblems.git
+        GIT_TAG ba099d6bd0ac186e4113fe340789a1800fa72852)
+        #SOURCE_DIR "${PROJECT_SOURCE_DIR}/../orproblems/")
+    FetchContent_MakeAvailable(orproblems)
+endif()