Adaptive Load fake time source

test/adaptive_load/BUILD

@@ -9,6 +9,26 @@ licenses(["notice"])  # Apache 2
 
 envoy_package()
 
+envoy_cc_test_library(
+    name = "fake_time_source",
+    srcs = ["fake_time_source.cc"],
+    hdrs = ["fake_time_source.h"],
+    repository = "@envoy",
+    deps = [
+        "//source/client:nighthawk_client_lib",
+        "@com_google_absl//absl/time",
+    ],
+)
+
+envoy_cc_test(
+    name = "fake_time_source_test",
+    srcs = ["fake_time_source_test.cc"],
+    repository = "@envoy",
+    deps = [
+        ":fake_time_source",
+    ],
+)
+
 envoy_cc_test_library(
     name = "minimal_output",
     srcs = ["minimal_output.cc"],

test/adaptive_load/fake_time_source.cc

@@ -0,0 +1,17 @@
+#include "test/adaptive_load/fake_time_source.h"
+
+namespace Nighthawk {
+
+Envoy::SystemTime FakeIncrementingMonotonicTimeSource::systemTime() {
+  Envoy::SystemTime epoch;
+  return epoch;
+}
+
+Envoy::MonotonicTime FakeIncrementingMonotonicTimeSource::monotonicTime() {
+  Envoy::MonotonicTime epoch;
+  Envoy::MonotonicTime result = epoch + std::chrono::seconds(seconds_since_epoch_);
+  ++seconds_since_epoch_;
+  return result;
+}
+
+} // namespace Nighthawk

test/adaptive_load/fake_time_source.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "envoy/common/time.h"
+
+namespace Nighthawk {
+/**
+ * Fake time source that ticks 1 second on every query, starting from the Unix epoch. Supports only
+ * monotonicTime().
+ */
+class FakeIncrementingMonotonicTimeSource : public Envoy::TimeSource {
+public:
+  /**
+   * Not supported.
+   *
+   * @return Envoy::SystemTime Fixed value of the Unix epoch.
+   */
+  Envoy::SystemTime systemTime() override;
+  /**
+   * Ticks forward 1 second on each call.
+   *
+   * @return Envoy::MonotonicTime Fake time value.
+   */
+  Envoy::MonotonicTime monotonicTime() override;
+
+private:
+  int seconds_since_epoch_{0};
+};
+
+} // namespace Nighthawk

test/adaptive_load/fake_time_source_test.cc

@@ -0,0 +1,32 @@
+#include "test/adaptive_load/fake_time_source.h"
+
+#include "gtest/gtest.h"
+
+namespace Nighthawk {
+namespace {
+
+TEST(FakeIncrementingMonotonicTimeSource, SystemTimeAlwaysReturnsEpoch) {
+  FakeIncrementingMonotonicTimeSource time_source;
+  Envoy::SystemTime epoch;
+  EXPECT_EQ(time_source.systemTime(), epoch);
+  EXPECT_EQ(time_source.systemTime(), epoch);
+}
+
+TEST(FakeIncrementingMonotonicTimeSource, MonotonicTimeStartsFromEpoch) {
+  FakeIncrementingMonotonicTimeSource time_source;
+  Envoy::MonotonicTime epoch;
+  Envoy::MonotonicTime time = time_source.monotonicTime();
+  EXPECT_EQ(std::chrono::duration_cast<std::chrono::seconds>(time - epoch).count(), 0);
+}
+
+TEST(FakeIncrementingMonotonicTimeSource, MonotonicTimeIncrementsOneSecondPerCall) {
+  FakeIncrementingMonotonicTimeSource time_source;
+  Envoy::MonotonicTime time1 = time_source.monotonicTime();
+  Envoy::MonotonicTime time2 = time_source.monotonicTime();
+  Envoy::MonotonicTime time3 = time_source.monotonicTime();
+  EXPECT_EQ(std::chrono::duration_cast<std::chrono::seconds>(time2 - time1).count(), 1);
+  EXPECT_EQ(std::chrono::duration_cast<std::chrono::seconds>(time3 - time2).count(), 1);
+}
+
+} // namespace
+} // namespace Nighthawk