Add testing namespace.

Working on Java client, will use this to spin up servers for running tests.

src/skywalker/server/testing.clj

@@ -0,0 +1,40 @@
+(ns skywalker.server.testing
+  (:require [skywalker.server :as server]
+            [skywalker.cluster :as cluster]
+            [clojure.core.async :as async]
+            [skywalker.cluster.client :as cc]
+            [skywalker.core :as core])
+  (:import (java.net InetSocketAddress InetAddress)
+           (java.security SecureRandom)))
+
+(defn test-server
+  "Create a single test server, bound to the loopback address and any port."
+  []
+  (server/server (InetSocketAddress. (InetAddress/getLoopbackAddress) 0)))
+
+(defn test-cluster
+  ([] (test-cluster 3))
+  ([num-servers]
+   (let [discovery-chans (mapv (fn [_] (async/chan)) (range num-servers))
+         discoveries (mapv #(reify cluster/Discovery
+                              (discover-nodes [_] %)
+                              (register-node [_ _] (async/go)))
+                           discovery-chans)
+         random (SecureRandom.)
+         tokens (mapv #(vec (for [_ (range 32)] (.nextLong random)))
+                      (range num-servers))
+         servers (mapv #(server/server (InetSocketAddress. (InetAddress/getLoopbackAddress) 0)
+                                       :tokens (nth tokens %)
+                                       :junction (cc/cluster-client (nth discoveries %)
+                                                                    {:tokens   (nth tokens %)
+                                                                     :junction (core/local-junction)}))
+                       (range num-servers))
+         nodes (mapv #(hash-map {:node/id (str "server" %)
+                                 :node/node (str "server" %)
+                                 :node/address ""
+                                 :service/address (.getHostAddress (InetAddress/getLoopbackAddress))
+                                 :service/port (:port (nth servers %))})
+                     (range num-servers))]
+     (doseq [chan discovery-chans]
+       (async/put! chan {:added-nodes nodes}))
+     servers)))