diff --git a/grails-app/controllers/rooms/AdminController.groovy b/grails-app/controllers/rooms/AdminController.groovy
deleted file mode 100644
index c11140a..0000000
--- a/grails-app/controllers/rooms/AdminController.groovy
+++ /dev/null
@@ -1,6 +0,0 @@
-package rooms
-
-class AdminController {
-
-    static scaffold = Admin
-}
diff --git a/grails-app/controllers/rooms/RoomController.groovy b/grails-app/controllers/rooms/RoomController.groovy
index ec3313b..4e59c17 100644
--- a/grails-app/controllers/rooms/RoomController.groovy
+++ b/grails-app/controllers/rooms/RoomController.groovy
@@ -4,25 +4,12 @@ class RoomController {
 
     static scaffold = Room
 
-    def tryRoom() {
-//        List<Room> rooms = Room.list()
-//        List<Room> rooms = Room.listOrderByCapacity()
-
-        Admin hans  = new Admin(name: "Hans",  tel: "1234", cardNumber: "1234").save()
-        Admin grete = new Admin(name: "Grete", tel: "4321", cardNumber: "4321").save()
-
-        new Room(name: "5.1C56", capacity: 40, admin: hans).save()
-        // java style
-//        for (int i = 0; i < 10; i++) {
-//            new Room(name: "Room " + i, capacity: i * 5).save()
-//        }
-        // groovy style
-        10.times { n ->
-            new Room(name: "Room " + n, capacity: n * 5, admin: grete).save()
-        }
+    def tryRoom() { // experiment with dynamic finder methods
 
+        List<Room> rooms = Room.list()
+//        List<Room> rooms = Room.listOrderByCapacity()
 //        List<Room> rooms = Room.findAllByCapacityGreaterThan(30)
-        List<Room> rooms = Room.findAllByAdmin(grete)
+
         String result = rooms.toString()
         render text: result
     }
diff --git a/grails-app/domain/rooms/Admin.groovy b/grails-app/domain/rooms/Admin.groovy
deleted file mode 100644
index 9923ec9..0000000
--- a/grails-app/domain/rooms/Admin.groovy
+++ /dev/null
@@ -1,18 +0,0 @@
-package rooms
-
-class Admin {
-
-    String name
-    String tel
-    String cardNumber
-
-    public String toString() {
-        return name;
-    }
-
-    static constraints = {
-        name        nullable: false, blank: false
-        tel         nullable: true
-        cardNumber  nullable: true
-    }
-}
diff --git a/grails-app/domain/rooms/Booking.groovy b/grails-app/domain/rooms/Booking.groovy
index 820b466..46c6119 100644
--- a/grails-app/domain/rooms/Booking.groovy
+++ b/grails-app/domain/rooms/Booking.groovy
@@ -2,10 +2,21 @@ package rooms
 
 class Booking {
 
+    String purpose = "Lecture"
     Person person
     Room   room
-    Date   bookingDate
+    Date   bookingDate   // a date where we ignore the time and assume 00:00:00
+    String timeslot      // one of AM, PM1, PM2
+
+    public static final String AM  = "08:15 - 11:00"
+    public static final String PM1 = "12:15 - 15:00"
+    public static final String PM2 = "15:15 - 18:00"
 
     static constraints = {
+        purpose     ()
+        person      nullable: false
+        room        nullable: false
+        bookingDate nullable: false
+        timeslot    nullable: false, inList: [AM, PM1, PM2]
     }
 }
diff --git a/grails-app/domain/rooms/Room.groovy b/grails-app/domain/rooms/Room.groovy
index 2021488..a39f37c 100644
--- a/grails-app/domain/rooms/Room.groovy
+++ b/grails-app/domain/rooms/Room.groovy
@@ -3,16 +3,14 @@ package rooms
 class Room {
     String name
     int    capacity
-    Admin  admin
 
     String toString() {
-        "$name ($capacity ${admin?.name})"                    // groovy style
-//        return name + " (" + capacity + ")"; // java style
+        "$name ($capacity)"                             // groovy style
+//        return name + " (" + capacity + ")";          // java style
     }
 
     static constraints = {
         name        nullable: false, blank: false
         capacity    min: 0
-        admin       nullable: true
     }
 }
diff --git a/src/main/resources/public/Jokes.html b/src/main/resources/public/Jokes.html
new file mode 100644
index 0000000..8efa0c4
--- /dev/null
+++ b/src/main/resources/public/Jokes.html
@@ -0,0 +1,41 @@
+<!doctype html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8"/>
+    <title>
+        Jokes
+    </title>
+    <script>
+        function getJokes() {
+            const url = "https://sv443.net/jokeapi/v2/joke/Programming";
+            fetch(url)
+                .then( resp => resp.json() )
+                .then( json => {
+                    console.log(json);
+                    let text = json.joke;
+                    if ("twopart" === json.type) { // Yoda conditional
+                        text = json.setup + " - "+ json.delivery;
+                    }
+                    document.getElementById("target").textContent = text ;
+                 })
+                .catch( err => console.log(err));
+        }
+    </script>
+</head>
+<body>
+<h1>
+    Programmer jokes from <a href="https://sv443.net/jokeapi">jokeapi</a>
+</h1>
+
+<button onclick="getJokes();">Next</button>
+
+<div id="target">
+    fetching ...
+</div>
+
+<script>
+    getJokes(); // initial load
+</script>
+
+</body>
+</html>
diff --git a/src/main/resources/public/Pictures.html b/src/main/resources/public/Pictures.html
new file mode 100644
index 0000000..a7063e3
--- /dev/null
+++ b/src/main/resources/public/Pictures.html
@@ -0,0 +1,58 @@
+<!doctype html>
+<html lang="en">
+<head>
+    <meta charset="UTF-8"/>
+    <title>
+        Pictures
+    </title>
+    <script>
+        let photoNumber = 0;
+        let pageNumber  = 1;
+        let photoInfos = undefined;
+
+        function nextPhoto() {
+            if (undefined === photoInfos) {
+                findInterestingImages();                // mutually recursive
+                return;
+            }
+            const photo = photoInfos[photoNumber++];
+            if (photoNumber > 10) {
+                // todo: what to do about the page number here?
+                photoNumber = 0;
+                findInterestingImages();
+                return;
+            }
+            const pictureUrl = "http://static.flickr.com/" +
+               photo.server + "/" +
+               photo.id + "_" +
+               photo.secret + "_m.jpg";
+            document.getElementById("target").innerHTML = "<img src='" +
+                                                          pictureUrl + "'><div> " +
+                                                          photo.title + "</div>";
+        }
+
+        function findInterestingImages() {
+            const url = "https://www.flickr.com/services/rest/?method=flickr.interestingness.getList&per_page=10&page=" +
+                        pageNumber + "&format=json&nojsoncallback=1&api_key=d5d6d15bb498e649b134170184968b61";
+            fetch(url)
+                .then( resp => resp.json() )
+                .then( json => {
+                    photoInfos = json.photos.photo;
+                    nextPhoto();
+                 })
+                .catch( err => console.log(err));
+        }
+    </script>
+</head>
+<body>
+<h1>
+    Pictures
+</h1>
+
+<div id="target" onclick="nextPhoto()">
+    Click me to find interesting images on flickr.
+</div>
+
+
+</body>
+</html>
\ No newline at end of file
diff --git a/src/test/groovy/rooms/BookingSpec.groovy b/src/test/groovy/rooms/BookingSpec.groovy
new file mode 100644
index 0000000..4429cd4
--- /dev/null
+++ b/src/test/groovy/rooms/BookingSpec.groovy
@@ -0,0 +1,57 @@
+package rooms
+
+import grails.testing.gorm.DomainUnitTest
+import spock.lang.Specification
+
+import static rooms.BootStrap.today
+
+class BookingSpec extends Specification implements DomainUnitTest<Booking> {
+    Person  john
+    Room    room_1
+    Booking booking_1
+
+    def setup() {
+        john   = new Person(firstName: "John", lastName: "Smith").save()
+        room_1 = new Room(name: "Room 1", capacity: 10).save()
+        booking_1 = new Booking(
+            person:         john,
+            room:           room_1,
+            bookingDate:    today,
+            timeslot:       Booking.AM)
+            .save()
+    }
+
+    def cleanup() {
+        john.delete()
+        room_1.delete()
+        booking_1.delete()
+    }
+
+    void "test constructor"() {
+        when:"sample data is loaded"
+            def bookings = Booking.list()
+
+        then:"there is a booking"
+            bookings.size() == 1
+    }
+
+    void "simple finder methods"() {
+        expect:
+        [booking_1] == Booking.findAllByPerson(john)
+        [booking_1] == Booking.findAllByRoom(room_1)
+        [booking_1] == Booking.findAllByBookingDate(today)
+        [booking_1] == Booking.findAllByTimeslot(Booking.AM)
+        []          == Booking.findAllByTimeslot(Booking.PM1)
+        "Lecture"   == Booking.findAllByPurpose("Lecture").first().purpose
+    }
+
+    void "find all names of all rooms booked by john"() {
+        expect:
+        ["Room 1"] == Booking.findAllByPerson(john).room.name
+    }
+
+    void "find the first names of all people that booked rooms today or in the future"() {
+        expect:
+        ["John"] == Booking.findAllByBookingDateGreaterThanEquals(today).person.firstName
+    }
+}
diff --git a/src/test/groovy/rooms/PersonSpec.groovy b/src/test/groovy/rooms/PersonSpec.groovy
new file mode 100644
index 0000000..8f3cc40
--- /dev/null
+++ b/src/test/groovy/rooms/PersonSpec.groovy
@@ -0,0 +1,24 @@
+package rooms
+
+import grails.testing.gorm.DomainUnitTest
+import spock.lang.Specification
+
+class PersonSpec extends Specification implements DomainUnitTest<Person> {
+
+    def setup() {
+    }
+
+    def cleanup() {
+    }
+
+    void "test constructor"() {
+        given :
+            new Person(firstName: "John", lastName: "Smith").save()
+            new Person(firstName: "Jane", lastName: "Doe").save()
+        when:"sample data is loaded"
+            def people = Person.list()
+
+        then:"there are 2 people"
+            people.size() == 2
+    }
+}
diff --git a/src/test/groovy/rooms/RoomSpec.groovy b/src/test/groovy/rooms/RoomSpec.groovy
new file mode 100644
index 0000000..4e652d5
--- /dev/null
+++ b/src/test/groovy/rooms/RoomSpec.groovy
@@ -0,0 +1,25 @@
+package rooms
+
+import grails.testing.gorm.DomainUnitTest
+import spock.lang.Specification
+
+class RoomSpec extends Specification implements DomainUnitTest<Room> {
+
+    def setup() {
+    }
+
+    def cleanup() {
+    }
+
+    void "test constructor"() {
+        given:
+            new Room(name: "Room 1", capacity: 10).save()
+            new Room(name: "Room 2", capacity: 20).save()
+            new Room(name: "Room 3", capacity: 30).save()
+        when:"sample data is loaded"
+            def rooms = Room.list()
+
+        then:"there are 3 rooms"
+            rooms.size() == 3
+    }
+}