MINOR: Add test cases to the Raft module (#12692)

Reviewers: Mickael Maison <mickael.maison@gmail.com>
, Divij Vaidya <diviv@amazon.com>, Ismael Juma <mlists@juma.me.uk>

raft/src/main/java/org/apache/kafka/raft/VotedState.java

@@ -92,11 +92,6 @@ public class VotedState implements EpochState {
         return electionTimer.isExpired();
     }
 
-    public void overrideElectionTimeout(long currentTimeMs, long timeoutMs) {
-        electionTimer.update(currentTimeMs);
-        electionTimer.reset(timeoutMs);
-    }
-
     @Override
     public boolean canGrantVote(int candidateId, boolean isLogUpToDate) {
         if (votedId() == candidateId) {

raft/src/test/java/org/apache/kafka/raft/ResignedStateTest.java

@@ -29,6 +29,7 @@ import java.util.Set;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 class ResignedStateTest {
@@ -90,4 +91,17 @@ class ResignedStateTest {
         assertFalse(state.canGrantVote(2, isLogUpToDate));
         assertFalse(state.canGrantVote(3, isLogUpToDate));
     }
+
+    @Test
+    void testNegativeScenarioAcknowledgeResignation() {
+        Set<Integer> voters = Utils.mkSet(0, 1, 2, 3, 4, 5);
+
+        ResignedState state = newResignedState(voters, Collections.emptyList());
+
+        assertEquals(ElectionState.withElectedLeader(epoch, 0, voters), state.election());
+        assertEquals(epoch, state.epoch());
+
+        // try non-existed voter must throw an exception
+        assertThrows(IllegalArgumentException.class, () -> state.acknowledgeResignation(10));
+    }
 }

raft/src/test/java/org/apache/kafka/raft/ValidOffsetAndEpochTest.java

@@ -0,0 +1,53 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.kafka.raft;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class ValidOffsetAndEpochTest {
+
+    @Test
+    void diverging() {
+        ValidOffsetAndEpoch validOffsetAndEpoch = ValidOffsetAndEpoch.diverging(new OffsetAndEpoch(0, 0));
+
+        assertEquals(ValidOffsetAndEpoch.Kind.DIVERGING, validOffsetAndEpoch.kind());
+    }
+
+    @Test
+    void snapshot() {
+        ValidOffsetAndEpoch validOffsetAndEpoch = ValidOffsetAndEpoch.snapshot(new OffsetAndEpoch(0, 0));
+
+        assertEquals(ValidOffsetAndEpoch.Kind.SNAPSHOT, validOffsetAndEpoch.kind());
+    }
+
+    @Test
+    void valid() {
+        ValidOffsetAndEpoch validOffsetAndEpoch = ValidOffsetAndEpoch.valid(new OffsetAndEpoch(0, 0));
+
+        assertEquals(ValidOffsetAndEpoch.Kind.VALID, validOffsetAndEpoch.kind());
+    }
+
+    @Test
+    void testValidWithoutSpecifyingOffsetAndEpoch() {
+        ValidOffsetAndEpoch validOffsetAndEpoch = ValidOffsetAndEpoch.valid();
+
+        assertEquals(ValidOffsetAndEpoch.Kind.VALID, validOffsetAndEpoch.kind());
+        assertEquals(new OffsetAndEpoch(-1, -1), validOffsetAndEpoch.offsetAndEpoch());
+    }
+}