Merge "Add ArbitraryJumpableGenerator tests." into main

1 files changed, 121 insertions, 0 deletions

diff --git a/luni/src/test/java/libcore/java/util/ArbitrarilyJumpableGeneratorTest.java b/luni/src/test/java/libcore/java/util/ArbitrarilyJumpableGeneratorTest.java
new file mode 100644
index 00000000000..bdd48e8cbe4
--- /dev/null
+++ b/luni/src/test/java/libcore/java/util/ArbitrarilyJumpableGeneratorTest.java
@@ -0,0 +1,121 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * 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 libcore.java.util;
+
+import static org.junit.Assert.assertEquals;
+
+import static java.util.stream.Collectors.toSet;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+import java.util.Set;
+import java.util.random.RandomGenerator;
+import java.util.stream.Collectors;
+
+@RunWith(JUnit4.class)
+public class ArbitrarilyJumpableGeneratorTest {
+
+    private static final class StubGenerator
+            implements RandomGenerator.ArbitrarilyJumpableGenerator {
+
+        private double state;
+
+        StubGenerator(double state) {
+            this.state = state;
+        }
+
+        @Override
+        public long nextLong() {
+            return 0;
+        }
+
+        @Override
+        public double jumpDistance() {
+            return 1.0d;
+        }
+
+        @Override
+        public double leapDistance() {
+            return 2.0d;
+        }
+
+        @Override
+        public ArbitrarilyJumpableGenerator copy() {
+            return new StubGenerator(state);
+        }
+
+        @Override
+        public void jumpPowerOfTwo(int logDistance) {
+            state += Math.pow(2, logDistance);
+        }
+
+        @Override
+        public void jump(double distance) {
+            state += distance;
+        }
+    }
+
+    @Test
+    public void jump_jumpsToJumpDistance() {
+        double initState = 10.0d;
+        StubGenerator rng = new StubGenerator(initState);
+
+        rng.jump();
+
+        assertEquals(initState + rng.jumpDistance(), rng.state, 0.001d);
+    }
+
+    @Test
+    public void leap_jumpsToLeapDistance() {
+        double initState = 10.0d;
+        StubGenerator rng = new StubGenerator(initState);
+
+        rng.leap();
+
+        assertEquals(initState + rng.leapDistance(), rng.state, 0.001d);
+    }
+
+    @Test
+    public void jump_advancesEachElementInStream() {
+        double initState = 1d;
+        StubGenerator rng = new StubGenerator(initState);
+
+        double jumpDistance = 10;
+        int streamSize = 5;
+
+        var generators = rng.jumps(streamSize, jumpDistance).toList();
+
+        assertEquals(initState + jumpDistance * streamSize, rng.state, 0.001d);
+        assertEquals(streamSize, generators.size());
+
+        Set<Double> actualStates = generators.stream()
+                .map(generator -> (StubGenerator) generator)
+                .map(stubGenerator -> stubGenerator.state)
+                .collect(toSet());
+
+        Set<Double> expectedStates = Set.of(
+                initState,
+                initState + jumpDistance,
+                initState + 2 * jumpDistance,
+                initState + 3 * jumpDistance,
+                initState + 4 * jumpDistance);
+
+        assertEquals(expectedStates, actualStates);
+    }
+}