From fbc9aeac2c652c347d9677977a6c1ced35f30960 Mon Sep 17 00:00:00 2001
From: Berack96 <giacomobertolazzi7@gmail.com>
Date: Fri, 7 Feb 2025 17:33:27 +0100
Subject: [PATCH] Refactor simulation and net example tests to use builder
 pattern for ServerNode and improve arrival handling logic

---
 .../upo/valpre/NetBuilderInteractive.java     |   4 +-
 .../net/berack/upo/valpre/sim/ServerNode.java | 196 ++++++++++++------
 .../net/berack/upo/valpre/sim/Simulation.java |   6 +-
 src/main/resources/example1.net               | Bin 396 -> 388 bytes
 src/main/resources/example2.net               | Bin 588 -> 580 bytes
 src/main/resources/example3.net               | Bin 487 -> 479 bytes
 .../upo/valpre/sim/TestSaveExamplesNet.java   |  95 +++++++--
 .../berack/upo/valpre/sim/TestSimulation.java | 127 ++++++++++--
 8 files changed, 329 insertions(+), 99 deletions(-)

diff --git a/src/main/java/net/berack/upo/valpre/NetBuilderInteractive.java b/src/main/java/net/berack/upo/valpre/NetBuilderInteractive.java
index d63e753..c510695 100644
--- a/src/main/java/net/berack/upo/valpre/NetBuilderInteractive.java
+++ b/src/main/java/net/berack/upo/valpre/NetBuilderInteractive.java
@@ -74,12 +74,12 @@ public class NetBuilderInteractive {
                 var limit = ask("Arrivals limit (0 for Int.Max): ", Integer::parseInt, 1);
                 if (limit <= 0)
                     limit = Integer.MAX_VALUE;
-                yield ServerNode.createLimitedSource(name, distribution, limit);
+                yield ServerNode.Builder.sourceLimited(name, limit, distribution);
             }
             case 2 -> {
                 var servers = ask("Number of servers: ", Integer::parseInt, 1);
                 var unavailable = askDistribution("Unavailable distribution");
-                yield ServerNode.createQueue(name, servers, distribution, unavailable);
+                yield ServerNode.Builder.queue(name, servers, distribution, unavailable);
             }
             default -> null;
         };
diff --git a/src/main/java/net/berack/upo/valpre/sim/ServerNode.java b/src/main/java/net/berack/upo/valpre/sim/ServerNode.java
index 9475b65..caa82c4 100644
--- a/src/main/java/net/berack/upo/valpre/sim/ServerNode.java
+++ b/src/main/java/net/berack/upo/valpre/sim/ServerNode.java
@@ -15,84 +15,36 @@ public class ServerNode {
     public final Distribution service;
     public final Distribution unavailable;
 
-    /**
-     * Creates a source node with the given name and distribution.
-     * It swpawns infinite arrivals (Integer.MAX_VALUE) that are served by infinite
-     * servers (Integer.MAX_VALUE).
-     * 
-     * @param name         The name of the node.
-     * @param distribution The distribution of the inter-arrival times.
-     * @return The created source node.
-     */
-    public static ServerNode createSource(String name, Distribution distribution) {
-        return new ServerNode(name, Integer.MAX_VALUE, distribution, null, Integer.MAX_VALUE);
-    }
-
-    /**
-     * Creates a source node with the given name, distribution, and number of
-     * arrivals to spawn that are served by infinite servers (Integer.MAX_VALUE).
-     * 
-     * @param name          The name of the node.
-     * @param service       The distribution of the inter-arrival times.
-     * @param spawnArrivals The number of arrivals to spawn.
-     * @return The created source node.
-     */
-    public static ServerNode createLimitedSource(String name, Distribution service, int spawnArrivals) {
-        return new ServerNode(name, Integer.MAX_VALUE, service, null, spawnArrivals);
-    }
-
-    /**
-     * Creates a queue node with the given name, maximum number of servers, and
-     * distribution.
-     * 
-     * @param name       The name of the node.
-     * @param maxServers The maximum number of servers in the queue.
-     * @param service    The distribution of the service times.
-     * @return The created queue node.
-     */
-    public static ServerNode createQueue(String name, int maxServers, Distribution service) {
-        return new ServerNode(name, maxServers, service, null, 0);
-    }
-
-    /**
-     * Creates a queue node with the given name, maximum number of servers, and
-     * distribution.
-     * 
-     * @param name        The name of the node.
-     * @param maxServers  The maximum number of servers in the queue.
-     * @param service     The distribution of the service times.
-     * @param unavailable The distribution of the unavailable times after service.
-     * @return The created queue node.
-     */
-    public static ServerNode createQueue(String name, int maxServers, Distribution service, Distribution unavailable) {
-        return new ServerNode(name, maxServers, service, unavailable, 0);
-    }
-
     /**
      * Creates a generic node with the given name and distribution.
      * The servers number must be 1 or higher; if lower will be put to 1.
      * The spawn number must be 0 or higher; if lower will be put to 0.
-     * The distribution can't be null, otherwise an exception is thrown.
+     * The queue number must be equal or higher than the servers number; if lower
+     * will be put to the servers number.
+     * The service distribution can't be null, otherwise an exception is thrown.
      * 
-     * @param name          The name of the node.
-     * @param maxServers    The maximum number of servers in the queue.
-     * @param service       The distribution of the service times.
-     * @param unavailable   The distribution of the unavailable times after service.
-     * @param spawnArrivals The number of arrivals to spawn.
+     * @param name        The name of the node.
+     * @param servers     The maximum number of servers in the queue.
+     * @param spawn       The number of arrivals to spawn.
+     * @param queue       The maximum number of requests in the queue.
+     * @param service     The distribution of the service times.
+     * @param unavailable The distribution of the unavailable times after service.
      * @throws NullPointerException if the distribution is null
      */
-    private ServerNode(String name, int maxServers, Distribution service, Distribution unavailable, int spawnArrivals) {
+    private ServerNode(String name, int servers, int spawn, int queue, Distribution service, Distribution unavailable) {
         if (service == null)
             throw new NullPointerException("Service distribution can't be null");
-        if (maxServers <= 0)
-            maxServers = 1;
-        if (spawnArrivals < 0)
-            spawnArrivals = 0;
+        if (servers <= 0)
+            servers = 1;
+        if (spawn < 0)
+            spawn = 0;
+        if (queue < servers)
+            queue = servers;
 
         this.name = name;
-        this.maxQueue = 100; // TODO change to runtime
-        this.maxServers = maxServers;
-        this.spawnArrivals = spawnArrivals;
+        this.maxQueue = queue;
+        this.maxServers = servers;
+        this.spawnArrivals = spawn;
         this.service = service;
         this.unavailable = unavailable;
     }
@@ -131,4 +83,114 @@ public class ServerNode {
     public int hashCode() {
         return this.name.hashCode();
     }
+
+    /**
+     * Creates a new builder for the node.
+     * It is useful to create a node with a more readable syntax and a in a more
+     * flexible way.
+     */
+    public static class Builder {
+        private String name;
+        private int maxQueue;
+        private int maxServers;
+        private int spawnArrivals;
+        private Distribution service;
+        private Distribution unavailable;
+
+        /**
+         * Creates a new builder for the node with the given name and distribution.
+         * The maximum number of servers is set to 1, the maximum number of requests in
+         * the queue is set to 100, the number of arrivals to spawn is set to 0, and
+         * the unavailable time is set to null.
+         * 
+         * @param name    The name of the node.
+         * @param service The distribution of the service times.
+         * @return The created sink node.
+         */
+        public Builder(String name, Distribution service) {
+            this.name = name;
+            this.service = service;
+            this.maxQueue = 100; // default value
+            this.maxServers = 1;
+            this.spawnArrivals = 0;
+            this.unavailable = null;
+        }
+
+        public Builder queue(int maxQueue) {
+            this.maxQueue = maxQueue;
+            return this;
+        }
+
+        public Builder servers(int maxServers) {
+            this.maxServers = maxServers;
+            return this;
+        }
+
+        public Builder spawn(int spawnArrivals) {
+            this.spawnArrivals = spawnArrivals;
+            return this;
+        }
+
+        public Builder unavailable(Distribution unavailable) {
+            this.unavailable = unavailable;
+            return this;
+        }
+
+        public ServerNode build() {
+            return new ServerNode(name, maxServers, spawnArrivals, maxQueue, service, unavailable);
+        }
+
+        /**
+         * Creates a source node with the given name and distribution.
+         * It swpawns infinite arrivals (Integer.MAX_VALUE) that are served by infinite
+         * servers (Integer.MAX_VALUE).
+         * 
+         * @param name         The name of the node.
+         * @param distribution The distribution of the inter-arrival times.
+         * @return The created source node.
+         */
+        public static ServerNode source(String name, Distribution distribution) {
+            return new Builder(name, distribution).spawn(Integer.MAX_VALUE).build();
+        }
+
+        /**
+         * Creates a source node with the given name, distribution, and number of
+         * arrivals to spawn that are served by infinite servers (Integer.MAX_VALUE).
+         * 
+         * @param name          The name of the node.
+         * @param service       The distribution of the inter-arrival times.
+         * @param spawnArrivals The number of arrivals to spawn.
+         * @return The created source node.
+         */
+        public static ServerNode sourceLimited(String name, int spawnArrivals, Distribution service) {
+            return new Builder(name, service).spawn(spawnArrivals).build();
+        }
+
+        /**
+         * Creates a queue node with the given name, maximum number of servers, and
+         * distribution.
+         * 
+         * @param name       The name of the node.
+         * @param maxServers The maximum number of servers in the queue.
+         * @param service    The distribution of the service times.
+         * @return The created queue node.
+         */
+        public static ServerNode queue(String name, int maxServers, Distribution service) {
+            return new Builder(name, service).servers(maxServers).build();
+        }
+
+        /**
+         * Creates a queue node with the given name, maximum number of servers, and
+         * distribution.
+         * 
+         * @param name        The name of the node.
+         * @param maxServers  The maximum number of servers in the queue.
+         * @param service     The distribution of the service times.
+         * @param unavailable The distribution of the unavailable times after service.
+         * @return The created queue node.
+         */
+        public static ServerNode queue(String name, int maxServers, Distribution service, Distribution unavailable) {
+            return new Builder(name, service).unavailable(unavailable).servers(maxServers).build();
+        }
+    }
 }
diff --git a/src/main/java/net/berack/upo/valpre/sim/Simulation.java b/src/main/java/net/berack/upo/valpre/sim/Simulation.java
index b1b3a61..40b2e50 100644
--- a/src/main/java/net/berack/upo/valpre/sim/Simulation.java
+++ b/src/main/java/net/berack/upo/valpre/sim/Simulation.java
@@ -97,8 +97,12 @@ public final class Simulation {
 
                 this.addToFel(state.spawnUnavailableIfPossible(time, this.rng));
                 this.addToFel(state.spawnDepartureIfPossible(time, this.rng));
-                this.addToFel(state.spawnArrivalToChild(time, this.rng));
                 this.addToFel(state.spawnArrivalIfPossilbe(time));
+
+                // Spawn arrival to child node if queue is not full otherwise drop
+                var ev = state.spawnArrivalToChild(time, this.rng);
+                if (ev != null && !this.states[ev.nodeIndex].isQueueFull())
+                    this.addToFel(ev);
             }
         }
     }
diff --git a/src/main/resources/example1.net b/src/main/resources/example1.net
index bd6b8bc80535ecd5af1baaefcaabe818cef506fa..52d954e3fe6912461d8b40f210efcf09a5a83d31 100644
GIT binary patch
delta 19
ZcmeBSZeiZQ$jHbvnT;_JNX9T4001fj1KI!p

delta 27
dcmZo+?qS}*$jJKd|NsB|lbIL;p{x)_0|20_3+4a-

diff --git a/src/main/resources/example2.net b/src/main/resources/example2.net
index e2139846d7d7266b878c36bb23f6ee8082cfe797..b7dc9d3823834ba88430d8b3083087edd2ef2e81 100644
GIT binary patch
delta 19
ZcmX@Za)f0=D<dP*<SxcQAo+kX2LM3H1|$Fg

delta 41
vcmX@Ya)xC?D<ki}|NsB<2j`a-B|l|kpEyx$;w_=c+ZYvD!Qzu|Fy;UNotG2l

diff --git a/src/main/resources/example3.net b/src/main/resources/example3.net
index cb933b0069521526f8df62a22f941a51a5cf8fa5..59f76645e7c23dbcf510ada684243864d310b028 100644
GIT binary patch
delta 19
ZcmaFPe4lwk79%6m<a|asAUTOK6aYV<1&ROw

delta 27
dcmcc5{G54179;Dw|NsB<PtInPgR;69Ljk}T4VC}^

diff --git a/src/test/java/net/berack/upo/valpre/sim/TestSaveExamplesNet.java b/src/test/java/net/berack/upo/valpre/sim/TestSaveExamplesNet.java
index 4f6d31d..5141031 100644
--- a/src/test/java/net/berack/upo/valpre/sim/TestSaveExamplesNet.java
+++ b/src/test/java/net/berack/upo/valpre/sim/TestSaveExamplesNet.java
@@ -1,5 +1,7 @@
 package net.berack.upo.valpre.sim;
 
+import static org.junit.Assert.assertEquals;
+
 import java.io.IOException;
 
 import org.junit.Test;
@@ -7,6 +9,8 @@ import org.junit.Test;
 import com.esotericsoftware.kryo.KryoException;
 
 import net.berack.upo.valpre.rand.Distribution;
+import net.berack.upo.valpre.rand.Rng;
+import net.berack.upo.valpre.sim.stats.NodeStats;
 
 public class TestSaveExamplesNet {
 
@@ -22,40 +26,103 @@ public class TestSaveExamplesNet {
     private static final Distribution unNorm = new Distribution.UnavailableTime(0.2, norm4_2);
     private static final Distribution unExp = new Distribution.UnavailableTime(0.1, exp10);
 
+    private static final int spawn = 10000;
+    private static final String path = "src/main/resources/example%d.%s";
+    private static final String net1 = path.formatted(1, "net");
+    private static final String net2 = path.formatted(2, "net");
+    private static final String net3 = path.formatted(3, "net");
+
     @Test
     public void testSaveExample1() throws KryoException, IOException {
         var net = new Net();
-        net.addNode(ServerNode.createLimitedSource("Source", exp0_22, 10000));
-        net.addNode(ServerNode.createQueue("Queue", 1, norm3_2));
+        net.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp0_22));
+        net.addNode(ServerNode.Builder.queue("Queue", 1, norm3_2));
         net.addConnection(0, 1, 1.0);
 
-        net.save("src/main/resources/example1.net");
-        net = Net.load("src/main/resources/example1.net");
+        net.save(net1);
+        net = Net.load(net1);
+
+        var sim = new Simulation(net, new Rng());
+        var res = sim.run();
+        var time = 44782.0;
+        var maxErr = time / 1000.0;
+
+        assertEquals(Rng.DEFAULT, res.seed);
+        assertEquals(time, res.simulationTime, maxErr);
+        testNode(res.nodes.get("Source"), 10000, time, 1.0, 4.5, 0.0, 0.0);
+        testNode(res.nodes.get("Queue"), 10000, time, 2.6, 7.2, 4.0, 0.0);
     }
 
     @Test
     public void testSaveExample2() throws KryoException, IOException {
         var net = new Net();
-        net.addNode(ServerNode.createLimitedSource("Source", exp0_22, 10000));
-        net.addNode(ServerNode.createQueue("Queue", 1, norm3_2));
-        net.addNode(ServerNode.createQueue("Queue Wait", 1, norm3_2, unNorm));
+        net.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp0_22));
+        net.addNode(ServerNode.Builder.queue("Queue", 1, norm3_2));
+        net.addNode(ServerNode.Builder.queue("Queue Wait", 1, norm3_2, unNorm));
         net.addConnection(0, 1, 1.0);
         net.addConnection(1, 2, 1.0);
 
-        net.save("src/main/resources/example2.net");
-        net = Net.load("src/main/resources/example2.net");
+        net.save(net2);
+        net = Net.load(net2);
+
+        var sim = new Simulation(net, new Rng());
+        var res = sim.run();
+        var time = 45417.0;
+        var maxErr = time / 1000.0;
+
+        assertEquals(Rng.DEFAULT, res.seed);
+        assertEquals(time, res.simulationTime, maxErr);
+        testNode(res.nodes.get("Source"), 10000, time, 1.0, 4.5, 0.0, 0.0);
+        testNode(res.nodes.get("Queue"), 10000, time, 2.6, 7.2, 4.0, 0.0);
+        testNode(res.nodes.get("Queue Wait"), 10000, time, 5.8, 22.3, 19.1, 8497.7);
     }
 
     @Test
     public void testSaveExample3() throws KryoException, IOException {
         var net = new Net();
-        net.addNode(ServerNode.createLimitedSource("Source", exp1_5, 10000));
-        net.addNode(ServerNode.createQueue("Service1", 1, exp2));
-        net.addNode(ServerNode.createQueue("Service2", 1, exp3_5, unExp));
+        net.addNode(ServerNode.Builder.sourceLimited("Source", spawn, exp1_5));
+        net.addNode(ServerNode.Builder.queue("Service1", 1, exp2));
+        net.addNode(ServerNode.Builder.queue("Service2", 1, exp3_5, unExp));
         net.addConnection(0, 1, 1.0);
         net.addConnection(1, 2, 1.0);
 
-        net.save("src/main/resources/example3.net");
-        net = Net.load("src/main/resources/example3.net");
+        net.save(net3);
+        net = Net.load(net3);
+
+        var sim = new Simulation(net, new Rng());
+        var res = sim.run();
+        var time = 6736.0;
+        var maxErr = time / 1000.0;
+
+        assertEquals(Rng.DEFAULT, res.seed);
+        assertEquals(time, res.simulationTime, maxErr);
+        testNode(res.nodes.get("Source"), 10000, time, 1.0, 0.6, 0.0, 0.0);
+        testNode(res.nodes.get("Service1"), 10000, time, 3.5, 1.7, 1.2, 0.0);
+        testNode(res.nodes.get("Service2"), 10000, time, 1.7, 0.5, 0.22, 102.2);
+    }
+
+    private void testNode(NodeStats stat, double numClients, double time, double avgQueue,
+            double avgResponse, double avgWait, double totalUnavailable) {
+        assertEquals("Num Arrivals", numClients, stat.numArrivals, 0.1);
+        assertEquals("Num Departures", numClients, stat.numDepartures, 0.1);
+
+        var maxErr = time / 1000.0;
+        assertEquals(time, stat.lastEventTime, maxErr);
+        assertEquals("Avg Queue", avgQueue, stat.avgQueueLength, 0.1);
+        assertEquals("Avg Wait", avgWait, stat.avgWaitTime, 0.1);
+        assertEquals("Avg Response", avgResponse, stat.avgResponse, 0.1);
+
+        var totalWait = numClients * stat.avgWaitTime;
+        var totalResponse = numClients * stat.avgResponse;
+        var totalBusy = totalResponse - totalWait;
+
+        assertEquals("Tot Wait", totalWait, stat.waitTime, maxErr);
+        assertEquals("Tot Response", totalResponse, stat.responseTime, maxErr);
+        assertEquals("Tot Busy", totalBusy, stat.busyTime, maxErr);
+        assertEquals("Tot Unavailable", totalUnavailable, stat.unavailableTime, maxErr);
+
+        assertEquals("Throughput", stat.numDepartures / stat.lastEventTime, stat.throughput, 0.001);
+        assertEquals("% Busy", stat.busyTime / stat.lastEventTime, stat.utilization, 0.001);
+        assertEquals("% Unavailable", stat.unavailableTime / stat.lastEventTime, stat.unavailable, 0.001);
     }
 }
diff --git a/src/test/java/net/berack/upo/valpre/sim/TestSimulation.java b/src/test/java/net/berack/upo/valpre/sim/TestSimulation.java
index a814618..4b97ae2 100644
--- a/src/test/java/net/berack/upo/valpre/sim/TestSimulation.java
+++ b/src/test/java/net/berack/upo/valpre/sim/TestSimulation.java
@@ -23,8 +23,8 @@ public class TestSimulation {
     private static final ServerNode node0;
     private static final ServerNode node1;
     static {
-        node0 = ServerNode.createLimitedSource("First", const1, 0);
-        node1 = ServerNode.createQueue("Second", 1, const1);
+        node0 = ServerNode.Builder.sourceLimited("First", 0, const1);
+        node1 = ServerNode.Builder.queue("Second", 1, const1);
 
         simpleNet = new Net();
         simpleNet.addNode(node0);
@@ -41,27 +41,27 @@ public class TestSimulation {
 
     @Test
     public void serverNode() {
-        var node = ServerNode.createQueue("Nodo", 0, const1);
+        var node = ServerNode.Builder.queue("Nodo", 0, const1);
         assertEquals("Nodo", node.name);
         assertEquals(1, node.maxServers);
         assertEquals(0, node.spawnArrivals);
         assertEquals(1.0, node.getServiceTime(null), DELTA);
 
-        node = ServerNode.createQueue("Queue", 50, const1);
+        node = ServerNode.Builder.queue("Queue", 50, const1);
         assertEquals("Queue", node.name);
         assertEquals(50, node.maxServers);
         assertEquals(0, node.spawnArrivals);
         assertEquals(1.0, node.getServiceTime(null), DELTA);
 
-        node = ServerNode.createSource("Source", const1);
+        node = ServerNode.Builder.source("Source", const1);
         assertEquals("Source", node.name);
-        assertEquals(Integer.MAX_VALUE, node.maxServers);
+        assertEquals(1, node.maxServers);
         assertEquals(Integer.MAX_VALUE, node.spawnArrivals);
         assertEquals(1.0, node.getServiceTime(null), DELTA);
 
-        node = ServerNode.createLimitedSource("Source", const1, 50);
+        node = ServerNode.Builder.sourceLimited("Source", 50, const1);
         assertEquals("Source", node.name);
-        assertEquals(Integer.MAX_VALUE, node.maxServers);
+        assertEquals(1, node.maxServers);
         assertEquals(50, node.spawnArrivals);
         assertEquals(1.0, node.getServiceTime(null), DELTA);
     }
@@ -93,7 +93,7 @@ public class TestSimulation {
         var net = new Net();
         assertEquals(0, net.size());
 
-        var node = ServerNode.createSource("First", const0);
+        var node = ServerNode.Builder.source("First", const0);
         var index = net.addNode(node);
         assertEquals(1, net.size());
         assertEquals(0, index);
@@ -101,7 +101,7 @@ public class TestSimulation {
         assertEquals(node, net.getNode("First"));
         assertEquals(index, net.getNodeIndex("First"));
 
-        var node1 = ServerNode.createQueue("Second", 1, const0);
+        var node1 = ServerNode.Builder.queue("Second", 1, const0);
         var index1 = net.addNode(node1);
         assertEquals(2, net.size());
         assertEquals(0, index);
@@ -126,7 +126,7 @@ public class TestSimulation {
         conn = net.getChildren(1);
         assertEquals(0, conn.size());
 
-        var node2 = ServerNode.createQueue("Third", 1, const0);
+        var node2 = ServerNode.Builder.queue("Third", 1, const0);
         net.addNode(node2);
         net.addConnection(0, 2, 1.0);
         conn = net.getChildren(0);
@@ -172,7 +172,104 @@ public class TestSimulation {
         assertFalse(state.hasRequests());
         assertFalse(state.shouldSpawnArrival());
 
-        // TODO better test
+        state.numServerBusy = 1;
+        assertEquals(1, state.numServerBusy);
+        assertFalse(state.canServe());
+        assertFalse(state.hasRequests());
+
+        state.numServerBusy = 0;
+        state.numServerUnavailable = 1;
+        assertEquals(1, state.numServerUnavailable);
+        assertFalse(state.canServe());
+        assertFalse(state.hasRequests());
+
+        state.queue.add(1.0);
+        assertEquals(1, state.queue.size());
+        assertTrue(state.hasRequests());
+        assertFalse(state.isQueueFull());
+
+        state.numServerUnavailable = 0;
+        state.numServerBusy = 0;
+        assertTrue(state.canServe());
+        assertTrue(state.hasRequests());
+        state.numServerBusy = 1;
+        state.queue.poll();
+        assertEquals(0, state.queue.size());
+        assertFalse(state.hasRequests());
+    }
+
+    @Test
+    public void nodeStatsUpdates() {
+        var net = new Net();
+        net.addNode(ServerNode.Builder.sourceLimited("Source", 50, const1));
+        net.addNode(node1);
+        net.addConnection(0, 1, 1.0);
+
+        var state = new ServerNodeState(0, net);
+
+        var event = state.spawnArrivalIfPossilbe(0);
+        assertNotNull(event);
+        assertEquals(0, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.stats.numDepartures, DELTA);
+        assertEquals(0, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+        assertEquals(Event.Type.ARRIVAL, event.type);
+        assertEquals(0, event.nodeIndex);
+        state.updateArrival(event.time);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.numServerBusy);
+
+        event = state.spawnDepartureIfPossible(event.time, rigged);
+        assertNotNull(event);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.stats.numDepartures, DELTA);
+        assertEquals(1, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+        assertEquals(Event.Type.DEPARTURE, event.type);
+        assertEquals(0, event.nodeIndex);
+        state.updateDeparture(event.time);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(1, state.stats.numDepartures, DELTA);
+        assertEquals(0, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+
+        state = new ServerNodeState(1, net);
+        event = state.spawnArrivalIfPossilbe(0);
+        assertNull(event);
+        assertEquals(0, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.stats.numDepartures, DELTA);
+        assertEquals(0, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+        state.updateArrival(0);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.numServerBusy);
+
+        event = state.spawnDepartureIfPossible(0, rigged);
+        assertNotNull(event);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.stats.numDepartures, DELTA);
+        assertEquals(1, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+        assertEquals(Event.Type.DEPARTURE, event.type);
+        assertEquals(1, event.nodeIndex);
+        state.updateDeparture(event.time);
+        assertEquals(1, state.stats.numArrivals, DELTA);
+        assertEquals(1, state.stats.numDepartures, DELTA);
+        assertEquals(0, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+
+        event = state.spawnUnavailableIfPossible(0, rigged);
+        assertNull(event);
+
+        state = new ServerNodeState(0, net);
+        event = state.spawnArrivalToChild(0, rigged);
+        assertNotNull(event);
+        assertEquals(0, state.stats.numArrivals, DELTA);
+        assertEquals(0, state.stats.numDepartures, DELTA);
+        assertEquals(0, state.numServerBusy);
+        assertEquals(0, state.numServerUnavailable);
+        assertEquals(Event.Type.ARRIVAL, event.type);
+        assertEquals(1, event.nodeIndex);
     }
 
     @Test
@@ -431,13 +528,13 @@ public class TestSimulation {
         assertEquals(6, res.nodes.get(node0.name).numArrivals, DELTA);
         assertEquals(5, res.nodes.get(node0.name).numDepartures, DELTA);
         assertEquals(4, res.nodes.get(node1.name).numArrivals, DELTA);
-        assertEquals(0, res.nodes.get(node1.name).numDepartures, DELTA);
+        assertEquals(3, res.nodes.get(node1.name).numDepartures, DELTA);
     }
 
     @Test
     public void simulationStats() {
         var net = new Net();
-        net.addNode(ServerNode.createLimitedSource("Source", const1, 50));
+        net.addNode(ServerNode.Builder.sourceLimited("Source", 50, const1));
 
         var sim = new Simulation(net, rigged);
         var result = sim.run();
@@ -454,7 +551,7 @@ public class TestSimulation {
         assertEquals(1.0, nodeStat.utilization, DELTA);
         assertEquals(0.0, nodeStat.unavailable, DELTA);
 
-        net.addNode(ServerNode.createQueue("Queue", 1, const1));
+        net.addNode(ServerNode.Builder.queue("Queue", 1, const1));
         net.addConnection(0, 1, 1.0);
 
         sim = new Simulation(net, rigged);