diff --git a/lib/pls/include/pls/internal/base/spin_lock.h b/lib/pls/include/pls/internal/base/spin_lock.h
index 4105e1c..880a521 100644
--- a/lib/pls/include/pls/internal/base/spin_lock.h
+++ b/lib/pls/include/pls/internal/base/spin_lock.h
@@ -26,6 +26,10 @@ namespace pls {
                         }
                     }
                 }
+
+                void unlock() {
+                    flag_.clear(std::memory_order_release);
+                }
             };
         }
     }
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0ca48e9..3532cbe 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -1,5 +1,5 @@
 add_executable(tests
         main.cpp
         example_tests.cpp
-        thread_tests.cpp)
-target_link_libraries(tests catch2 pls)
\ No newline at end of file
+        base_tests.cpp)
+target_link_libraries(tests catch2 pls)
diff --git a/test/base_tests.cpp b/test/base_tests.cpp
new file mode 100644
index 0000000..d3c5ba9
--- /dev/null
+++ b/test/base_tests.cpp
@@ -0,0 +1,59 @@
+#include <catch.hpp>
+#include <pls/internal/base/thread.h>
+#include <pls/internal/base/spin_lock.h>
+
+#include <vector>
+
+using namespace pls::internal::base;
+using namespace std;
+
+static bool base_tests_visited;
+static int base_tests_local_value_one;
+static vector<int> base_tests_local_value_two;
+
+TEST_CASE( "thread creation and joining", "[internal/base/thread.h]") {
+    base_tests_visited = false;
+    auto t1 = start_thread([]() { base_tests_visited = true; });
+    t1.join();
+
+    REQUIRE(base_tests_visited);
+}
+
+TEST_CASE( "thread state", "[internal/base/thread.h]") {
+    int state_one = 1;
+    vector<int> state_two{1, 2};
+
+    auto t1 = start_thread([]() { base_tests_local_value_one = *this_thread::state<int>(); }, &state_one);
+    auto t2 = start_thread([]() { base_tests_local_value_two = *this_thread::state<vector<int>>(); }, &state_two);
+    t1.join();
+    t2.join();
+
+    REQUIRE(base_tests_local_value_one == 1);
+    REQUIRE(base_tests_local_value_two == vector<int>{1, 2});
+}
+
+TEST_CASE( "spinlock protects concurrent counter", "[internal/base/spinlock.h]") {
+    constexpr int num_iterations = 1000000;
+    int shared_counter = 0;
+    spin_lock lock{};
+
+    auto t1 = start_thread([&] () {
+       for (int i = 0; i < num_iterations; i++) {
+            lock.lock();
+            shared_counter++;
+            lock.unlock();
+       }
+    });
+    auto t2 = start_thread([&] () {
+        for (int i = 0; i < num_iterations; i++) {
+            lock.lock();
+            shared_counter--;
+            lock.unlock();
+        }
+    });
+
+    t1.join();
+    t2.join();
+
+    REQUIRE(shared_counter == 0);
+}
diff --git a/test/thread_tests.cpp b/test/thread_tests.cpp
deleted file mode 100644
index 03809fe..0000000
--- a/test/thread_tests.cpp
+++ /dev/null
@@ -1,32 +0,0 @@
-#include <catch.hpp>
-#include <pls/internal/base/thread.h>
-
-#include <vector>
-
-using namespace pls::internal::base;
-using namespace std;
-
-static bool visited;
-static int local_value_1;
-static vector<int> local_value_two;
-
-TEST_CASE( "thread creation and joining", "[internal/base/thread.h]") {
-    visited = false;
-    auto t1 = start_thread([]() { visited = true; });
-    t1.join();
-
-    REQUIRE(visited);
-}
-
-TEST_CASE( "thread state", "[internal/base/thread.h]") {
-    int state_one = 1;
-    vector<int> state_two{1, 2};
-    
-    auto t1 = start_thread([]() { local_value_1 = *this_thread::state<int>(); }, &state_one);
-    auto t2 = start_thread([]() { local_value_two = *this_thread::state<vector<int>>(); }, &state_two);
-    t1.join();
-    t2.join();
-
-    REQUIRE(local_value_1 == 1);
-    REQUIRE(local_value_two == vector<int>{1, 2});
-}