Move TestClock in opencensus-testing package. (#368)

2 files changed, 161 insertions, 0 deletions

diff --git a/testing/src/main/java/io/opencensus/testing/common/TestClock.java b/testing/src/main/java/io/opencensus/testing/common/TestClock.java
new file mode 100644
index 00000000..2a604f2a
--- /dev/null
+++ b/testing/src/main/java/io/opencensus/testing/common/TestClock.java
@@ -0,0 +1,99 @@
+/*
+ * Copyright 2017, Google Inc.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.testing.common;
+
+import com.google.common.math.LongMath;
+import io.opencensus.common.Clock;
+import io.opencensus.common.Duration;
+import io.opencensus.common.Timestamp;
+import javax.annotation.concurrent.GuardedBy;
+import javax.annotation.concurrent.ThreadSafe;
+
+/** A {@link Clock} that allows the time to be set for testing. */
+@ThreadSafe
+public final class TestClock extends Clock {
+  private static final int NUM_NANOS_PER_SECOND = 1000 * 1000 * 1000;
+
+  @GuardedBy("this")
+  private Timestamp currentTime = validateNanos(Timestamp.create(1493419949, 223123456));
+
+  private TestClock() {}
+
+  /**
+   * Creates a clock initialized to a constant non-zero time. {@code Timestamp.create(0, 0)} is not
+   * a good default, because it represents an invalid time.
+   *
+   * @return a clock initialized to a constant non-zero time.
+   */
+  public static TestClock create() {
+    return new TestClock();
+  }
+
+  /**
+   * Creates a clock with the given time.
+   *
+   * @param time the initial time.
+   * @return a new {@code TestClock} with the given time.
+   */
+  public static TestClock create(Timestamp time) {
+    TestClock clock = new TestClock();
+    clock.setTime(time);
+    return clock;
+  }
+
+  /**
+   * Sets the time.
+   *
+   * @param time the new time.
+   */
+  public synchronized void setTime(Timestamp time) {
+    currentTime = validateNanos(time);
+  }
+
+  /**
+   * Advances the time by a duration.
+   *
+   * @param duration the increase in time.
+   */
+  // TODO(sebright): Consider adding an 'addDuration' method to Timestamp.
+  public synchronized void advanceTime(Duration duration) {
+    currentTime =
+        validateNanos(
+            Timestamp.create(
+                    LongMath.checkedAdd(currentTime.getSeconds(), duration.getSeconds()),
+                    currentTime.getNanos())
+                .addNanos(duration.getNanos()));
+  }
+
+  @Override
+  public synchronized Timestamp now() {
+    return currentTime;
+  }
+
+  @Override
+  public synchronized long nowNanos() {
+    return getNanos(currentTime);
+  }
+
+  private static Timestamp validateNanos(Timestamp time) {
+    getNanos(time);
+    return time;
+  }
+
+  // Converts Timestamp into nanoseconds since time 0 and throws an exception if it overflows.
+  private static long getNanos(Timestamp time) {
+    return LongMath.checkedAdd(
+        LongMath.checkedMultiply(time.getSeconds(), NUM_NANOS_PER_SECOND), time.getNanos());
+  }
+}
diff --git a/testing/src/test/java/io/opencensus/testing/common/TestClockTest.java b/testing/src/test/java/io/opencensus/testing/common/TestClockTest.java
new file mode 100644
index 00000000..f67080c7
--- /dev/null
+++ b/testing/src/test/java/io/opencensus/testing/common/TestClockTest.java
@@ -0,0 +1,62 @@
+/*
+ * Copyright 2017, Google Inc.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opencensus.testing.common;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import io.opencensus.common.Duration;
+import io.opencensus.common.Timestamp;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link TestClock}. */
+@RunWith(JUnit4.class)
+public final class TestClockTest {
+  private static final int NUM_NANOS_PER_SECOND = 1000 * 1000 * 1000;
+
+  @Test
+  public void setAndGetTime() {
+    TestClock clock = TestClock.create(Timestamp.create(1, 2));
+    assertThat(clock.now()).isEqualTo(Timestamp.create(1, 2));
+    clock.setTime(Timestamp.create(3, 4));
+    assertThat(clock.now()).isEqualTo(Timestamp.create(3, 4));
+  }
+
+  @Test
+  public void advanceTime() {
+    TestClock clock = TestClock.create(Timestamp.create(1, 500 * 1000 * 1000));
+    clock.advanceTime(Duration.create(2, 600 * 1000 * 1000));
+    assertThat(clock.now()).isEqualTo(Timestamp.create(4, 100 * 1000 * 1000));
+  }
+
+  @Test
+  public void measureElapsedTime() {
+    TestClock clock = TestClock.create(Timestamp.create(10, 1));
+    long nanos1 = clock.nowNanos();
+    clock.setTime(Timestamp.create(11, 5));
+    long nanos2 = clock.nowNanos();
+    assertThat(nanos2 - nanos1).isEqualTo(1000 * 1000 * 1000 + 4);
+  }
+
+  @Test(expected = ArithmeticException.class)
+  public void catchOverflow() {
+    TestClock.create(Timestamp.create(Long.MAX_VALUE / NUM_NANOS_PER_SECOND + 1, 0));
+  }
+
+  @Test(expected = ArithmeticException.class)
+  public void catchNegativeOverflow() {
+    TestClock.create(Timestamp.create(Long.MIN_VALUE / NUM_NANOS_PER_SECOND - 1, 0));
+  }
+}