[wpilib] Add Notifier test (#5070)

wpilibc/src/test/native/cpp/NotifierTest.cpp

@@ -0,0 +1,52 @@
+// Copyright (c) FIRST and other WPILib contributors.
+// Open Source Software; you can modify and/or share it under the terms of
+// the WPILib BSD license file in the root directory of this project.
+
+#include <atomic>
+
+#include "frc/Notifier.h"
+#include "frc/simulation/SimHooks.h"
+#include "gtest/gtest.h"
+
+using namespace frc;
+
+namespace {
+
+class NotifierTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    sim::PauseTiming();
+    sim::RestartTiming();
+  }
+
+  void TearDown() override { sim::ResumeTiming(); }
+};
+
+}  // namespace
+
+TEST_F(NotifierTest, StartPeriodicAndStop) {
+  std::atomic<uint32_t> counter{0};
+
+  Notifier notifier{[&] { ++counter; }};
+  notifier.StartPeriodic(1_s);
+
+  sim::StepTiming(10.5_s);
+
+  notifier.Stop();
+  EXPECT_EQ(10u, counter);
+
+  sim::StepTiming(3_s);
+
+  EXPECT_EQ(10u, counter);
+}
+
+TEST_F(NotifierTest, StartSingle) {
+  std::atomic<uint32_t> counter{0};
+
+  Notifier notifier{[&] { ++counter; }};
+  notifier.StartSingle(1_s);
+
+  sim::StepTiming(10.5_s);
+
+  EXPECT_EQ(1u, counter);
+}