Add unit tests for RuntimeScheduler::now

Summary:
changelog: [internal]

Add unit tests for `RuntimeScheduler::now`

Reviewed By: JoshuaGross

Differential Revision: D27763852

fbshipit-source-id: 1edec8e8338e9d9798b95c55d07114be05f555b8

ReactCommon/react/renderer/runtimescheduler/RuntimeScheduler.cpp

@@ -10,7 +10,12 @@
 namespace facebook::react {
 
 RuntimeScheduler::RuntimeScheduler(RuntimeExecutor const &runtimeExecutor)
-    : runtimeExecutor_(runtimeExecutor) {}
+    : RuntimeScheduler(runtimeExecutor, RuntimeSchedulerClock::now) {}
+
+RuntimeScheduler::RuntimeScheduler(
+    RuntimeExecutor const &runtimeExecutor,
+    std::function<RuntimeSchedulerTimePoint()> now)
+    : runtimeExecutor_(runtimeExecutor), now_(now) {}
 
 std::shared_ptr<Task> RuntimeScheduler::scheduleTask(
     SchedulerPriority priority,
@@ -36,8 +41,8 @@ bool RuntimeScheduler::getShouldYield() const {
   return shouldYield_;
 }
 
-RuntimeSchedulerClock::time_point RuntimeScheduler::now() const {
-  return RuntimeSchedulerClock::now();
+RuntimeSchedulerTimePoint RuntimeScheduler::now() const {
+  return now_();
 }
 
 } // namespace facebook::react

ReactCommon/react/renderer/runtimescheduler/RuntimeScheduler.h

@@ -11,7 +11,6 @@
 #include <react/renderer/runtimescheduler/RuntimeSchedulerClock.h>
 #include <react/renderer/runtimescheduler/Task.h>
 #include <atomic>
-#include <chrono>
 #include <memory>
 #include <queue>
 
@@ -20,6 +19,9 @@ namespace facebook::react {
 class RuntimeScheduler final {
  public:
   RuntimeScheduler(RuntimeExecutor const &runtimeExecutor);
+  RuntimeScheduler(
+      RuntimeExecutor const &runtimeExecutor,
+      std::function<RuntimeSchedulerTimePoint()> now);
 
   std::shared_ptr<Task> scheduleTask(
       SchedulerPriority priority,
@@ -29,7 +31,7 @@ class RuntimeScheduler final {
 
   bool getShouldYield() const;
 
-  RuntimeSchedulerClock::time_point now() const;
+  RuntimeSchedulerTimePoint now() const;
 
  private:
   mutable std::priority_queue<
@@ -39,6 +41,7 @@ class RuntimeScheduler final {
       taskQueue_;
   RuntimeExecutor const runtimeExecutor_;
   std::atomic_bool shouldYield_{false};
+  std::function<RuntimeSchedulerTimePoint()> now_;
 };
 
 } // namespace facebook::react

ReactCommon/react/renderer/runtimescheduler/RuntimeSchedulerClock.h

@@ -16,4 +16,7 @@ namespace facebook::react {
  */
 using RuntimeSchedulerClock = std::chrono::steady_clock;
 
+using RuntimeSchedulerTimePoint = RuntimeSchedulerClock::time_point;
+using RuntimeSchedulerDuration = RuntimeSchedulerClock::duration;
+
 } // namespace facebook::react

ReactCommon/react/renderer/runtimescheduler/tests/RuntimeSchedulerTest.cpp

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+#include <react/renderer/runtimescheduler/RuntimeScheduler.h>
+#include "StubClock.h"
+
+using namespace facebook::react;
+using namespace std::chrono_literals;
+
+TEST(RuntimeSchedulerTest, now) {
+  facebook::jsi::Runtime *runtime;
+
+  RuntimeExecutor runtimeExecutor =
+      [&runtime](
+          std::function<void(facebook::jsi::Runtime & runtime)> &&callback) {
+        // TODO: This will crash if executed.
+        callback(*runtime);
+      };
+
+  auto stubClock = StubClock();
+  stubClock.setTimePoint(1ms);
+
+  auto stubNow = [&stubClock]() -> RuntimeSchedulerTimePoint {
+    return stubClock.getNow();
+  };
+
+  auto runtimeScheduler = RuntimeScheduler(runtimeExecutor, stubNow);
+  EXPECT_EQ(runtimeScheduler.now(), RuntimeSchedulerTimePoint(1ms));
+
+  stubClock.advanceTimeBy(10ms);
+
+  EXPECT_EQ(runtimeScheduler.now(), RuntimeSchedulerTimePoint(11ms));
+
+  stubClock.advanceTimeBy(6s);
+
+  EXPECT_EQ(runtimeScheduler.now(), RuntimeSchedulerTimePoint(6011ms));
+}

ReactCommon/react/renderer/runtimescheduler/tests/StubClock.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#pragma once
+
+#include <react/renderer/runtimescheduler/RuntimeSchedulerClock.h>
+#include <chrono>
+
+namespace facebook::react {
+
+class StubClock {
+ public:
+  RuntimeSchedulerTimePoint getNow() const {
+    return timePoint_;
+  }
+
+  void setTimePoint(RuntimeSchedulerTimePoint timePoint) {
+    timePoint_ = timePoint;
+  }
+
+  void setTimePoint(RuntimeSchedulerDuration duration) {
+    timePoint_ = RuntimeSchedulerTimePoint(duration);
+  }
+
+  RuntimeSchedulerTimePoint getTimePoint() {
+    return timePoint_;
+  }
+
+  void advanceTimeBy(RuntimeSchedulerDuration duration) {
+    timePoint_ += duration;
+  }
+
+ private:
+  RuntimeSchedulerTimePoint timePoint_;
+};
+
+} // namespace facebook::react