2 files changed, 76 insertions, 0 deletions
diff --git a/tests/unit/libutil/async-semaphore.cc b/tests/unit/libutil/async-semaphore.cc
new file mode 100644
index 000000000..12b52885d
--- /dev/null
+++ b/tests/unit/libutil/async-semaphore.cc
@@ -0,0 +1,74 @@
+#include "async-semaphore.hh"
+
+#include <gtest/gtest.h>
+#include <kj/async.h>
+
+namespace nix {
+
+TEST(AsyncSemaphore, counting)
+{
+    kj::EventLoop loop;
+    kj::WaitScope waitScope(loop);
+
+    AsyncSemaphore sem(2);
+
+    ASSERT_EQ(sem.available(), 2);
+    ASSERT_EQ(sem.used(), 0);
+
+    auto a = kj::evalNow([&] { return sem.acquire(); });
+    ASSERT_EQ(sem.available(), 1);
+    ASSERT_EQ(sem.used(), 1);
+    auto b = kj::evalNow([&] { return sem.acquire(); });
+    ASSERT_EQ(sem.available(), 0);
+    ASSERT_EQ(sem.used(), 2);
+
+    auto c = kj::evalNow([&] { return sem.acquire(); });
+    auto d = kj::evalNow([&] { return sem.acquire(); });
+
+    ASSERT_TRUE(a.poll(waitScope));
+    ASSERT_TRUE(b.poll(waitScope));
+    ASSERT_FALSE(c.poll(waitScope));
+    ASSERT_FALSE(d.poll(waitScope));
+
+    a = nullptr;
+    ASSERT_TRUE(c.poll(waitScope));
+    ASSERT_FALSE(d.poll(waitScope));
+
+    {
+        auto lock = b.wait(waitScope);
+        ASSERT_FALSE(d.poll(waitScope));
+    }
+
+    ASSERT_TRUE(d.poll(waitScope));
+
+    ASSERT_EQ(sem.available(), 0);
+    ASSERT_EQ(sem.used(), 2);
+    c = nullptr;
+    ASSERT_EQ(sem.available(), 1);
+    ASSERT_EQ(sem.used(), 1);
+    d = nullptr;
+    ASSERT_EQ(sem.available(), 2);
+    ASSERT_EQ(sem.used(), 0);
+}
+
+TEST(AsyncSemaphore, cancelledWaiter)
+{
+    kj::EventLoop loop;
+    kj::WaitScope waitScope(loop);
+
+    AsyncSemaphore sem(1);
+
+    auto a = kj::evalNow([&] { return sem.acquire(); });
+    auto b = kj::evalNow([&] { return sem.acquire(); });
+    auto c = kj::evalNow([&] { return sem.acquire(); });
+
+    ASSERT_TRUE(a.poll(waitScope));
+    ASSERT_FALSE(b.poll(waitScope));
+
+    b = nullptr;
+    a = nullptr;
+
+    ASSERT_TRUE(c.poll(waitScope));
+}
+
+}
diff --git a/tests/unit/meson.build b/tests/unit/meson.build
index 8ff0b5ec5..5baf10de2 100644
--- a/tests/unit/meson.build
+++ b/tests/unit/meson.build
@@ -39,6 +39,7 @@ liblixutil_test_support = declare_dependency(
 )
 
 libutil_tests_sources = files(
+  'libutil/async-semaphore.cc',
   'libutil/canon-path.cc',
   'libutil/checked-arithmetic.cc',
   'libutil/chunked-vector.cc',
@@ -76,6 +77,7 @@ libutil_tester = executable(
     liblixexpr_mstatic,
     liblixutil_test_support,
     nlohmann_json,
+    kj,
   ],
   cpp_pch : cpp_pch,
 )