Add tests for tokens protocol

Modules/Example Replication/jvm/src/test/scala/replication/protocols/TokensTest.scala

@@ -0,0 +1,64 @@
+package replication.protocols
+
+import rdts.time.Dots
+import rdts.base.{Lattice, Uid}
+import rdts.datatypes.contextual.ReplicatedSet
+import rdts.dotted.Dotted
+import rdts.syntax.LocalReplicaId
+
+class TokensTest extends munit.FunSuite {
+  given dots: Dots             = Dots.empty
+  given Lattice[Dotted[Token]] = Lattice.derived
+  val numOfReplicas            = 5
+  val replicas: Seq[LocalReplicaId] = List.tabulate(numOfReplicas)(_ => LocalReplicaId.gen())
+  var token = Dotted(Token(
+    os = Ownership.unchanged,
+    wants = ReplicatedSet.empty
+  ))
+  // set replica 0 the initial owner
+  token = token.merge(Dotted(Token(Ownership(1, LocalReplicaId.unwrap(replicas(0))), ReplicatedSet.empty)))
+
+  test("Some replica initially owns the token") {
+    assert(List.range(0, numOfReplicas).map(n => token.data.isOwner(using replicas(n))).reduce((x, y) => x || y))
+  }
+  test("Owner doesn't change if no replica wants the token") {
+    // replica 0, the current owner, calls upkeep
+    val updatedToken = token.merge(Dotted(token.data.upkeep(using replicas(0))))
+    // wants is empty, owner should remain same
+    assert(updatedToken.data.isOwner(using replicas(0)))
+  }
+  test("Interested replica with the biggest id gets the token next") {
+    // replicas 2 and 3 request token
+    var updatedToken = token.merge(token.data.request(using replicas(1)))
+    updatedToken = updatedToken.merge(updatedToken.data.request(using replicas(2)))
+    // find biggest id in wants
+    val biggestIdIndex = replicas.indexOf(LocalReplicaId.predefined(updatedToken.data.wants.elements.max))
+    // replica 0, the current owner, calls upkeep
+    updatedToken = updatedToken.merge(Dotted(updatedToken.data.upkeep(using replicas(0))))
+    // assert that the new owner is the one with the biggest id
+    assert(updatedToken.data.isOwner(using replicas(biggestIdIndex)))
+  }
+  test("Replica that isn't the owner can't change owner") {
+    // replica 1 is not the owner and calls upkeep
+    val updatedToken = token.merge(Dotted(token.data.upkeep(using replicas(1))))
+    assert(updatedToken.data.isOwner(using replicas(0)))
+  }
+  test("Owner can't choose itself as the next owner if other replicas interested") {
+    // replica 1 interested
+    var updatedToken = token.merge(token.data.request(using replicas(1)))
+    // replica 0 calls upkeep, 1 should be the new owner
+    updatedToken = updatedToken.merge(Dotted(updatedToken.data.upkeep(using replicas(0))))
+    // assert that replica 0 is not the new owner
+    assert(!updatedToken.data.isOwner(using replicas(0)))
+  }
+  test("Replica that never requested can't be chosen to be the owner") {
+    // replicas 1 & 2 request the token
+    var updatedToken = token.merge(token.data.request(using replicas(1)))
+    updatedToken = updatedToken.merge(token.data.request(using replicas(2)))
+    // replica 0 calls upkeep
+    updatedToken = updatedToken.merge(Dotted(updatedToken.data.upkeep(using replicas(0))))
+    // assert neither replica 3 nor 4 were chosen to be the owner
+    assert(!updatedToken.data.isOwner(using replicas(3)) &&
+      !updatedToken.data.isOwner(using replicas(4)))
+  }
+}