Find an available port for test server

Was hardcoded to 8888, but this port can, of course, be in use for other
things.

test/etaoin/api_test.clj

@@ -10,7 +10,8 @@
    [etaoin.api :as e]
    [etaoin.impl.util :as util]
    [etaoin.test-report :as test-report]
-   [slingshot.slingshot :refer [try+]]))
+   [slingshot.slingshot :refer [try+]])
+  (:import [java.net ServerSocket]))
 
 (defn numeric? [val]
   (or (instance? Double val)
@@ -50,7 +51,11 @@
 
 (def ^:dynamic *driver*)
 
-(def test-server-port 8888)
+(defn- find-available-port []
+  (with-open [sock (ServerSocket. 0)]
+    (.getLocalPort sock)))
+
+(def test-server-port (find-available-port))
 
 (defn- test-server-url [path]
   (format "http://localhost:%d/%s" test-server-port path))
@@ -77,7 +82,8 @@
   (f))
 
 (defn test-server [f]
-  (let [proc (p/process "bb test-server")]
+  (let [proc (p/process {:out :inherit :err :inherit}
+                        "bb test-server --port" test-server-port)]
     (f)
     (p/destroy proc)
     @proc))