Add SimulationClockTest

Author: David Legg

contrib/src/main/java/gov/nasa/jpl/aerie/contrib/streamline/modeling/clocks/InstantClock.java

@@ -18,6 +18,8 @@ public InstantClock step(Duration t) {
         return new InstantClock(addToInstant(extract, t));
     }
 
+    // TODO - this method belongs somewhere else...
+    //  Making it package-private at least lets us move it later without dependency issues outside the library.
     static Duration durationBetween(Instant start, Instant end) {
         return Duration.of(ChronoUnit.MICROS.between(start, end), Duration.MICROSECONDS);
     }

contrib/src/test/java/gov/nasa/jpl/aerie/contrib/streamline/modeling/clocks/SimulationClockTest.java

@@ -0,0 +1,66 @@
+package gov.nasa.jpl.aerie.contrib.streamline.modeling.clocks;
+
+import gov.nasa.jpl.aerie.contrib.streamline.core.Resources;
+import gov.nasa.jpl.aerie.merlin.framework.junit.MerlinExtension;
+import gov.nasa.jpl.aerie.merlin.protocol.types.Duration;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.junit.jupiter.api.extension.ExtendWith;
+
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+
+import static gov.nasa.jpl.aerie.contrib.streamline.core.Resources.*;
+import static gov.nasa.jpl.aerie.merlin.framework.ModelActions.delay;
+import static gov.nasa.jpl.aerie.merlin.protocol.types.Duration.HOUR;
+import static gov.nasa.jpl.aerie.merlin.protocol.types.Duration.ZERO;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+@ExtendWith(MerlinExtension.class)
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+public class SimulationClockTest {
+    // This time is unlikely to be a hard-coded default anywhere
+    public static final Instant PLAN_START = Instant.parse("2020-01-02T03:04:05Z");
+
+    public SimulationClockTest() {
+        Resources.init(PLAN_START);
+    }
+
+    @Test
+    public void relative_clock_starts_at_zero() {
+        assertEquals(ZERO, currentTime());
+        assertEquals(ZERO, currentValue(simulationClock()));
+    }
+
+    @Test
+    public void absolute_clock_starts_at_plan_start() {
+        assertEquals(PLAN_START, currentInstant());
+        assertEquals(PLAN_START, currentValue(absoluteClock()));
+    }
+
+    @Test
+    public void relative_clock_advances_at_unit_rate() {
+        delay(1, HOUR);
+        assertEquals(Duration.of(1, HOUR), currentTime());
+        assertEquals(Duration.of(1, HOUR), currentValue(simulationClock()));
+        delay(1, HOUR);
+        assertEquals(Duration.of(2, HOUR), currentTime());
+        assertEquals(Duration.of(2, HOUR), currentValue(simulationClock()));
+        delay(1, HOUR);
+        assertEquals(Duration.of(3, HOUR), currentTime());
+        assertEquals(Duration.of(3, HOUR), currentValue(simulationClock()));
+    }
+
+    @Test
+    public void absolute_clock_advances_at_unit_rate() {
+        delay(1, HOUR);
+        assertEquals(PLAN_START.plus(1, ChronoUnit.HOURS), currentInstant());
+        assertEquals(PLAN_START.plus(1, ChronoUnit.HOURS), currentValue(absoluteClock()));
+        delay(1, HOUR);
+        assertEquals(PLAN_START.plus(2, ChronoUnit.HOURS), currentInstant());
+        assertEquals(PLAN_START.plus(2, ChronoUnit.HOURS), currentValue(absoluteClock()));
+        delay(1, HOUR);
+        assertEquals(PLAN_START.plus(3, ChronoUnit.HOURS), currentInstant());
+        assertEquals(PLAN_START.plus(3, ChronoUnit.HOURS), currentValue(absoluteClock()));
+    }
+}