diff --git a/README.md b/README.md
index 49659b0..3ecd628 100644
--- a/README.md
+++ b/README.md
@@ -3,6 +3,7 @@
 REST service for the creation and modification of nondeterministic finite automaton for the automatic generation of GUI tests with the help of a genetic algorithm.
 The service hides the actual implementation and defines a fixed interface for calls.
 Therefore, calling systems do not depend on the concrete implementation and it can be mocked easily for tests.
+Basically, it does only provide only the two calls `getState` and `executeAction`.
 
 ## Automatic Build with TravisCI
 [![Build Status](https://travis-ci.org/retest/gui-state-machine-api.svg?branch=master)](https://travis-ci.org/retest/gui-state-machine-api)
@@ -56,29 +57,6 @@ A state is defined by the set of all visible and interactable windows together w
 ## Scala API for GUI State Machines
 The package [api](./src/main/scala/de/retest/guistatemachine/api/) contains all types and methods for getting and modifying the GUI state machine.
 
-## DSL
-There is a DSL to construct an NFA with GUI actions manually.
-The package [dsl](./src/main/scala/de/retest/guistatemachine/dsl/).
-
-The following example shows how to construct an NFA in Scala:
-```scala
-case object Start extends InitialState
-case object S0 extends State
-case object S1 extends State
-case object End extends FinalState
-case object EnterText extends Action
-case object PressExitButton extends Action
-
-StateMachines {
-  StateMachine {
-    Start - EnterText - S0
-    Start - EnterText - S1
-    S0 - PressExitButton - End
-    S1 - PressExitButton - End
-  }
-}
-```
-
 ## REST API
 Some suggestions how the REST API for the state machine could look like:
 * `/state-machines` GET queries all existing state machines.
@@ -90,19 +68,8 @@ Some suggestions how the REST API for the state machine could look like:
 * `/state-machine/<long>/state/<long>/transition/<long>` GET queries a specific transition of a specific state.
 * `/state-machine/<long>/execute` POST executes the passed action from the passed state which might lead to a new state and adds a transition to the state machine. The action must be part of all actions?
 
-Some suggestions on how the test representation REST API could look like (not necessarily required):
-
-* `/applications` GET queries all existing GUI applications.
-* `/create-application` POST creates a new GUI application.
-* `/application/<long>` GET queries an existing GUI application.
-* `/application/<long>` DELETE deletes an existing GUI application and all of its test suites etc.
-* `/application/<long>/test-suites` GET queries all test suites for an existing GUI application.
-* `/application/<long>/create-test-suite` POST creates a new test suite for an existing GUI application.
-* `/application/<long>/test-suite/<long>` GET queries an existing test suite for an existing GUI application.
-* `/application/<long>/test-suite/<long>` DELETE deletes an existing test suite for an existing GUI application.
-
-## NFA Frameworks
-This list contains frameworks for Scala which support the representation of an NFA:
+## Possible NFA Frameworks
+This list contains frameworks for Scala which support the representation of an NFA and could be used as backend to construct the state machine:
 * Akka FSM (FSM for actors): <https://doc.akka.io/docs/akka/current/fsm.html>
 * Neo4J: <https://neo4j.com/>
 * Gremlin-Scala: <https://github.com/mpollmeier/gremlin-scala>
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/Action.scala b/src/main/scala/de/retest/guistatemachine/api/Action.scala
index f5ceecf..1b6f7f1 100644
--- a/src/main/scala/de/retest/guistatemachine/api/Action.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/Action.scala
@@ -3,4 +3,8 @@ package de.retest.guistatemachine.api
 /**
   * Interaction from the user with the GUI.
   */
-case class Action(a : org.openqa.selenium.interactions.Action)
\ No newline at end of file
+case class Action(a: org.openqa.selenium.interactions.Action) {
+
+  // TODO #5 Convert abstract representation of actions into string.
+  override def toString: String = "Selenium Action"
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/Descriptors.scala b/src/main/scala/de/retest/guistatemachine/api/Descriptors.scala
index 8a9d050..d52701e 100644
--- a/src/main/scala/de/retest/guistatemachine/api/Descriptors.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/Descriptors.scala
@@ -5,4 +5,4 @@ import de.retest.ui.descriptors.RootElement
 /**
   * Set of root elements which identifies a state.
   */
-case class Descriptors(rootElements: Set[RootElement])
+case class Descriptors(rootElements: Set[RootElement])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/GuiStateMachine.scala b/src/main/scala/de/retest/guistatemachine/api/GuiStateMachine.scala
index 8d73700..7517580 100644
--- a/src/main/scala/de/retest/guistatemachine/api/GuiStateMachine.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/GuiStateMachine.scala
@@ -26,4 +26,4 @@ trait GuiStateMachine {
     * @return The current state which the transition of a leads to.
     */
   def executeAction(from: State, a: Action, descriptors: Descriptors, neverExploredActions: Set[Action]): State
-}
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/GuiStateMachineApi.scala b/src/main/scala/de/retest/guistatemachine/api/GuiStateMachineApi.scala
new file mode 100644
index 0000000..9a88725
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/api/GuiStateMachineApi.scala
@@ -0,0 +1,17 @@
+package de.retest.guistatemachine.api
+
+trait GuiStateMachineApi {
+
+  /**
+    * Creates a new [[GuiStateMachine]].
+    * @return The new GUI state machine.
+    */
+  def createStateMachine: GuiStateMachine
+
+  /**
+    * Removes a persisted [[GuiStateMachine]].
+    * @param stateMachine The persisted GUI state machine.
+    * @return True if it has been persisted before and is no remove. Otherwise, false.
+    */
+  def removeStateMachine(stateMachine: GuiStateMachine): Boolean
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/State.scala b/src/main/scala/de/retest/guistatemachine/api/State.scala
index 1f7fdab..87c65db 100644
--- a/src/main/scala/de/retest/guistatemachine/api/State.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/State.scala
@@ -5,6 +5,8 @@ package de.retest.guistatemachine.api
   * It consists of actions which have not been explored yet and transitions which build up the state machine.
   */
 trait State {
+  def getDescriptors: Descriptors
+
   def getNeverExploredActions: Set[Action]
 
   /**
@@ -12,4 +14,29 @@ trait State {
     * Hence, we have a set of states per action.
     */
   def getTransitions: Map[Action, Set[State]]
-}
+
+  /**
+    * Adds a new transition to the state which is only allowed by calling the methods of [[GuiStateMachine]].
+    * @param a The action which represents the transition's consumed symbol.
+    * @param to The state which the transition leads t o.
+    */
+  private[api] def addTransition(a: Action, to: State): Unit
+
+  /**
+    * Overriding this method is required to allow the usage of a set of states.
+    * Comparing the descriptors should check for the equality of all root elements which compares the identifying attributes and the contained components
+    * for each root element.
+    */
+  override def equals(obj: Any): Boolean = {
+    if (obj.isInstanceOf[State]) {
+      val other = obj.asInstanceOf[State]
+      this.getDescriptors == other.getDescriptors
+    } else {
+      super.equals(obj)
+    }
+  }
+
+  override def hashCode(): Int = this.getDescriptors.hashCode()
+
+  override def toString: String = s"descriptors=${getDescriptors},neverExploredActions=${getNeverExploredActions},transitions=${getTransitions}"
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImpl.scala b/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImpl.scala
new file mode 100644
index 0000000..c440e39
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImpl.scala
@@ -0,0 +1,19 @@
+package de.retest.guistatemachine.api.impl
+
+import de.retest.guistatemachine.api.GuiStateMachineApi
+import de.retest.guistatemachine.api.GuiStateMachine
+
+import scala.collection.mutable.HashSet
+
+object GuiStateMachineApiImpl extends GuiStateMachineApi {
+  // TODO #4 Use Persistence instead of a custom set?
+  val stateMachines = new HashSet[GuiStateMachine]
+
+  override def createStateMachine: GuiStateMachine = {
+    val r = new GuiStateMachineImpl
+    stateMachines += r
+    r
+  }
+
+  override def removeStateMachine(stateMachine: GuiStateMachine): Boolean = stateMachines.remove(stateMachine)
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImpl.scala b/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImpl.scala
index fb2481c..61e7235 100644
--- a/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImpl.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImpl.scala
@@ -4,7 +4,7 @@ import de.retest.guistatemachine.api.{Action, Descriptors, GuiStateMachine, Stat
 
 import scala.collection.mutable.HashMap
 
-object GuiStateMachineImpl extends GuiStateMachine {
+class GuiStateMachineImpl extends GuiStateMachine {
   val states = new HashMap[Descriptors, State]
 
   override def getState(descriptors: Descriptors, neverExploredActions: Set[Action]): State = {
@@ -19,7 +19,7 @@ object GuiStateMachineImpl extends GuiStateMachine {
 
   override def executeAction(from: State, a: Action, descriptors: Descriptors, neverExploredActions: Set[Action]): State = {
     val to = getState(descriptors, neverExploredActions)
-    from.asInstanceOf[StateImpl].addTransition(a, to)
+    from.addTransition(a, to)
     to
   }
-}
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/api/impl/StateImpl.scala b/src/main/scala/de/retest/guistatemachine/api/impl/StateImpl.scala
index 118cee3..2556093 100644
--- a/src/main/scala/de/retest/guistatemachine/api/impl/StateImpl.scala
+++ b/src/main/scala/de/retest/guistatemachine/api/impl/StateImpl.scala
@@ -7,36 +7,21 @@ import scala.collection.immutable.{HashMap, HashSet}
 class StateImpl(val descriptors: Descriptors, var neverExploredActions: Set[Action]) extends State {
 
   /**
-    * TODO #4 Currently, there is no MultiMap trait for immutable maps.
+    * TODO #4 Currently, there is no MultiMap trait for immutable maps in the Scala standard library.
     */
   var transitions = new HashMap[Action, Set[State]]
 
+  override def getDescriptors: Descriptors = descriptors
   override def getNeverExploredActions: Set[Action] = neverExploredActions
   override def getTransitions: Map[Action, Set[State]] = transitions
 
-  def addTransition(a: Action, to: State): Unit = {
+  private[api] override def addTransition(a: Action, to: State): Unit = {
     if (!transitions.contains(a)) {
       transitions = transitions + (a -> HashSet(to))
-      // TODO #4 This is not done in the legacy code:
+      // In the legacy code this is done in `increaseTimesExecuted`.
       neverExploredActions = neverExploredActions - a
     } else {
       transitions = transitions + (a -> (transitions(a) + to))
     }
   }
-
-  /**
-    * Overriding this method is required to allow the usage of a set of states.
-    * Comparing the descriptors should check for the equality of all root elements which compares the identifying attributes and the contained components
-    * for each root element.
-    */
-  override def equals(obj: Any): Boolean = {
-    if (obj.isInstanceOf[StateImpl]) {
-      val other = obj.asInstanceOf[StateImpl]
-      this.descriptors == other.descriptors
-    } else {
-      super.equals(obj)
-    }
-  }
-
-  override def hashCode(): Int = this.descriptors.hashCode()
-}
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/Action.scala b/src/main/scala/de/retest/guistatemachine/dsl/Action.scala
deleted file mode 100644
index 2378220..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/Action.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-trait Action
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/FinalState.scala b/src/main/scala/de/retest/guistatemachine/dsl/FinalState.scala
deleted file mode 100644
index b008214..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/FinalState.scala
+++ /dev/null
@@ -1,6 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-/**
- * NFAs can have more than one final state.
- */
-trait FinalState extends State
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/InitialState.scala b/src/main/scala/de/retest/guistatemachine/dsl/InitialState.scala
deleted file mode 100644
index fdbb4b2..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/InitialState.scala
+++ /dev/null
@@ -1,6 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-/**
- * NFAs have only one initial state.
- */
-trait InitialState extends State
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/State.scala b/src/main/scala/de/retest/guistatemachine/dsl/State.scala
deleted file mode 100644
index ecd7763..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/State.scala
+++ /dev/null
@@ -1,30 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-import scala.collection.mutable.ListBuffer
-
-trait State {
-  /**
-   * The previous state has to be stored for the DSL only to reach the initial state.
-   */
-  private[dsl] var previous: State = null
-  // TODO Use a set instead of a list buffer? Actually it is a multi map with the action as key and multiple possible states as values.
-  private[dsl] var transitions: ListBuffer[Transition] = ListBuffer.empty[Transition]
-
-  def getTransitions: Seq[Transition] = transitions
-
-  /**
-   * Goes back to the initial state from the current state and returns it.
-   */
-  def getInitial: InitialState = {
-    def getFirst: State = if (previous eq null) this else previous.getInitial
-
-    getFirst.asInstanceOf[InitialState]
-  }
-
-  // TODO Rename to ->
-  def -(a: Action): Transition = {
-    val t = Transition(this, a)
-    transitions += t
-    t
-  }
-}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/StateMachine.scala b/src/main/scala/de/retest/guistatemachine/dsl/StateMachine.scala
deleted file mode 100644
index 398192b..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/StateMachine.scala
+++ /dev/null
@@ -1,50 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-import scala.collection.immutable.HashSet
-
-/**
- * NFA:
- * 5–Tupel (Z, Σ, δ, z0, E)
- * TODO NFAs can have multiple initial states. Do we really need this?
- * TODO Make the constructor private.
- */
-case class StateMachine(initial: InitialState, var previous: StateMachine) {
-
-  def getInitial: InitialState = initial
-
-  /**
-   * Appends another state machine.
-   */
-  def ~(s: StateMachine): StateMachine = {
-    s.previous = this
-    s
-  }
-
-  /**
-   * All states.
-   */
-  //def Z(): Set[State]
-  /**
-   * Input alphabet.
-   */
-  //def Σ(): Set[Action]
-  /**
-   * Partially defined function which returns the next state.
-   */
-  //def δ(s: State, a: Action): State
-  /**
-   * Initial state.
-   * TODO NFAs can have multiple initial states. Do we really need this?
-   */
-  //def z0: InitialState = initial
-
-  /**
-   * All final states.
-   */
-  //def E: Set[FinalState]
-}
-
-object StateMachine {
-  // TODO f should return a FinalState since all state machines have to end with one
-  def apply(f: => State): StateMachine = StateMachine(f.getInitial, null)
-}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/StateMachines.scala b/src/main/scala/de/retest/guistatemachine/dsl/StateMachines.scala
deleted file mode 100644
index ab5bf16..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/StateMachines.scala
+++ /dev/null
@@ -1,25 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-import scala.collection.immutable.HashMap
-
-object StateMachines {
-  def apply(f: => StateMachine): Seq[StateMachine] = {
-    def constructSeq(s: StateMachine, seq: Seq[StateMachine]): Seq[StateMachine] =
-      if (s.previous ne null) constructSeq(s.previous, Seq(s) ++ seq) else Seq(s) ++ seq
-
-    constructSeq(f, Seq())
-  }
-
-  def toModel(s: Seq[StateMachine]): de.retest.guistatemachine.model.StateMachines = {
-    val hashmap = new HashMap[de.retest.guistatemachine.model.Id, de.retest.guistatemachine.model.StateMachine]()
-
-    // TODO Implement conversion from the DSL to the model.
-    /*
-    s.foreach(x => {
-      de.retest.guistatemachine.model.StateMachine
-    })
-    */
-
-    de.retest.guistatemachine.model.StateMachines(de.retest.guistatemachine.model.Map[de.retest.guistatemachine.model.StateMachine](hashmap))
-  }
-}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/Transition.scala b/src/main/scala/de/retest/guistatemachine/dsl/Transition.scala
deleted file mode 100644
index cb36d66..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/Transition.scala
+++ /dev/null
@@ -1,15 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-// TODO Make constructor private pls
-case class Transition(from: State, a: Action, var to: State = null) {
-
-  def getAction: Action = a
-  def getTo: State = to
-
-  // TODO Rename to ->
-  def -(to: State): State = {
-    to.previous = from
-    this.to = to
-    to
-  }
-}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/dsl/UnknownState.scala b/src/main/scala/de/retest/guistatemachine/dsl/UnknownState.scala
deleted file mode 100644
index db09e64..0000000
--- a/src/main/scala/de/retest/guistatemachine/dsl/UnknownState.scala
+++ /dev/null
@@ -1,6 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-/**
- * All actions can be executed for an unknown state.
- */
-case object UnknownState extends State
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Action.scala b/src/main/scala/de/retest/guistatemachine/model/Action.scala
deleted file mode 100644
index 08c8b74..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/Action.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-case class Action()
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Actions.scala b/src/main/scala/de/retest/guistatemachine/model/Actions.scala
deleted file mode 100644
index 69df23f..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/Actions.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-case class Actions(actions: Map[Action])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/GuiApplication.scala b/src/main/scala/de/retest/guistatemachine/model/GuiApplication.scala
deleted file mode 100644
index f7a5189..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/GuiApplication.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-final case class GuiApplication(testSuites: TestSuites)
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/GuiApplications.scala b/src/main/scala/de/retest/guistatemachine/model/GuiApplications.scala
deleted file mode 100644
index 3314403..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/GuiApplications.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-final case class GuiApplications(apps: Map[GuiApplication])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Map.scala b/src/main/scala/de/retest/guistatemachine/model/Map.scala
deleted file mode 100644
index 705177c..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/Map.scala
+++ /dev/null
@@ -1,14 +0,0 @@
-package de.retest.guistatemachine.model
-
-/**
- * This custom type allows storing values using [[Id]] as key.
- * [[JsonFormatForIdMap]] implements marshalling and unmarshalling for JSON for this type.
- * We cannot extend immutable maps in Scala, so we have to keep it as field.
- */
-case class Map[T](var values: scala.collection.immutable.Map[Id, T]) {
-  /**
-   * Generates a new ID based on the existing entries.
-   * TODO Generate IDs in a better way. Maybe random numbers until one unused element is found?
-   */
-  def generateId: Id = this.synchronized { if (values.isEmpty) Id(0) else Id(values.keySet.max.id + 1) }
-}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/State.scala b/src/main/scala/de/retest/guistatemachine/model/State.scala
deleted file mode 100644
index c115b92..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/State.scala
+++ /dev/null
@@ -1,5 +0,0 @@
-package de.retest.guistatemachine.model
-
-import scala.collection.immutable.HashMap
-
-final case class State(transitions: Transitions)
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/StateMachine.scala b/src/main/scala/de/retest/guistatemachine/model/StateMachine.scala
deleted file mode 100644
index 6b33275..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/StateMachine.scala
+++ /dev/null
@@ -1,6 +0,0 @@
-package de.retest.guistatemachine.model
-
-/**
- * State machine which represents a GUI test.
- */
-final case class StateMachine(states: States, actions: Actions)
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/States.scala b/src/main/scala/de/retest/guistatemachine/model/States.scala
deleted file mode 100644
index 585ece9..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/States.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-case class States(states: Map[State])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/TestSuite.scala b/src/main/scala/de/retest/guistatemachine/model/TestSuite.scala
deleted file mode 100644
index 27b104f..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/TestSuite.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-final case class TestSuite()
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/TestSuites.scala b/src/main/scala/de/retest/guistatemachine/model/TestSuites.scala
deleted file mode 100644
index bc22830..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/TestSuites.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-final case class TestSuites(suites: Map[TestSuite])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Transitions.scala b/src/main/scala/de/retest/guistatemachine/model/Transitions.scala
deleted file mode 100644
index b7a60b0..0000000
--- a/src/main/scala/de/retest/guistatemachine/model/Transitions.scala
+++ /dev/null
@@ -1,3 +0,0 @@
-package de.retest.guistatemachine.model
-
-final case class Transitions(transitions: Map[Transition])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/persistence/Persistence.scala b/src/main/scala/de/retest/guistatemachine/persistence/Persistence.scala
index fc5eaa8..c5b4d6e 100644
--- a/src/main/scala/de/retest/guistatemachine/persistence/Persistence.scala
+++ b/src/main/scala/de/retest/guistatemachine/persistence/Persistence.scala
@@ -1,106 +1,19 @@
 package de.retest.guistatemachine.persistence
 
-import scala.collection.immutable.HashMap
+import de.retest.guistatemachine.rest.model.{Id, Map, StateMachine, StateMachines}
 
-import de.retest.guistatemachine.model.GuiApplication
-import de.retest.guistatemachine.model.GuiApplications
-import de.retest.guistatemachine.model.Id
-import de.retest.guistatemachine.model.TestSuite
-import de.retest.guistatemachine.model.TestSuites
-import de.retest.guistatemachine.model.Map
-import de.retest.guistatemachine.model.StateMachines
-import de.retest.guistatemachine.model.StateMachine
+import scala.collection.immutable.HashMap
 
-/**
- * Allows concurrent access to the persistence of the resources.
- * The actual persistence layer is hidden by this class.
- */
 class Persistence {
   // database
   private val stateMachines = StateMachines(Map(new HashMap[Id, StateMachine]))
-  private val guiApplications = GuiApplications(Map(new HashMap[Id, GuiApplication]))
 
   def getStateMachines(): StateMachines = stateMachines
 
-  def getApplications(): GuiApplications = guiApplications
-
-  def addApplication(): Id = {
-    val apps = guiApplications
-    apps.synchronized {
-      val id = apps.apps.generateId
-      apps.apps.values = apps.apps.values + (id -> GuiApplication(TestSuites(Map(new HashMap[Id, TestSuite]))))
-      id
-    }
-  }
-  def getApplication(id: Id): Option[GuiApplication] = {
-    val apps = guiApplications
-    apps.synchronized {
-      if (apps.apps.values.contains(id)) Some(apps.apps.values(id)) else { None }
-    }
-  }
-
-  def deleteApplication(id: Id): Boolean = {
-    val apps = guiApplications
-    apps.synchronized {
-      if (apps.apps.values.contains(id)) {
-        apps.apps.values = apps.apps.values - id
-        true
-      } else {
-        false
-      }
-    }
-  }
-
-  def getTestSuites(applicationId: Id): Option[TestSuites] = {
-    val app = getApplication(applicationId)
-    app match {
-      case Some(x) => Some(x.testSuites)
-      case None => None
-    }
-  }
+  def getStateMachine(id: Id): Option[StateMachine] = if (stateMachines.stateMachines.hasElement(id)) Some(stateMachines.stateMachines.getElement(id)) else None
 
-  def addTestSuite(applicationId: Id): Option[Id] = {
-    val app = getApplication(applicationId)
-    app match {
-      case Some(x) => {
-        val testSuites = x.testSuites
-        testSuites.synchronized {
-          val id = testSuites.suites.generateId
-          testSuites.suites.values = testSuites.suites.values + (id -> TestSuite())
-          Some(id)
-        }
-      }
-      case None => None
-    }
-  }
-  def getTestSuite(applicationId: Id, testSuiteId: Id): Option[TestSuite] = {
-    val app = getApplication(applicationId)
-    app match {
-      case Some(x) => {
-        val testSuites = x.testSuites
-        testSuites.synchronized {
-          if (testSuites.suites.values.contains(testSuiteId)) Some(testSuites.suites.values(testSuiteId)) else None
-        }
-      }
-      case None => None
-    }
-  }
+  // TODO #4 Pass all unexplored actions for the initial state!
+  def createStateMachine(): Id = stateMachines.stateMachines.addNewElement(StateMachine())
 
-  def deleteTestSuite(applicationId: Id, testSuiteId: Id): Boolean = {
-    val app = getApplication(applicationId)
-    app match {
-      case Some(x) => {
-        val testSuites = x.testSuites
-        testSuites.synchronized {
-          if (testSuites.suites.values.contains(testSuiteId)) {
-            testSuites.suites.values = testSuites.suites.values - testSuiteId
-            true
-          } else {
-            false
-          }
-        }
-      }
-      case None => false
-    }
-  }
+  def deleteStateMachine(id: Id): Boolean = stateMachines.stateMachines.removeElement(id)
 }
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/JsonFormatForIdMap.scala b/src/main/scala/de/retest/guistatemachine/rest/JsonFormatForIdMap.scala
index 8cba7fc..0194428 100644
--- a/src/main/scala/de/retest/guistatemachine/rest/JsonFormatForIdMap.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/JsonFormatForIdMap.scala
@@ -1,30 +1,27 @@
 package de.retest.guistatemachine.rest
 
-import de.retest.guistatemachine.model.Map
-import de.retest.guistatemachine.model.Id
-import spray.json.JsValue
-import spray.json.JsonFormat
-import spray.json.RootJsonFormat
+import de.retest.guistatemachine.rest.model.Id
+import spray.json.{JsValue, JsonFormat, RootJsonFormat}
 
 /**
-  * Transforms a [[de.retest.guistatemachine.model.Map]] into a `scala.collection.immutable.Map[String, T]`, so it can be converted into valid JSON.
-  * Besides, transforms a JSON object which is a `scala.collection.immutable.Map[String, T]` back into a [[de.retest.guistatemachine.model.Map]].
+  * Transforms a [[model.Map]] into a `scala.collection.immutable.Map[String, T]`, so it can be converted into valid JSON.
+  * Besides, transforms a JSON object which is a `scala.collection.immutable.Map[String, T]` back into a [[model.Map]].
   * This transformer requires a JSON format for the type `K`.
   */
 class JsonFormatForIdMap[T](implicit
                             val jsonFormat0: JsonFormat[scala.collection.immutable.Map[String, T]],
                             implicit val jsonFormat1: JsonFormat[T])
-    extends RootJsonFormat[Map[T]] {
+    extends RootJsonFormat[model.Map[T]] {
 
-  override def write(obj: Map[T]): JsValue =
+  override def write(obj: model.Map[T]): JsValue =
     jsonFormat0.write(obj.values.map { field =>
       (field._1.id.toString -> field._2)
     })
 
-  override def read(json: JsValue): Map[T] = {
+  override def read(json: JsValue): model.Map[T] = {
     val map = jsonFormat0.read(json)
-    new Map[T](map.map { x =>
+    new model.Map[T](map.map { x =>
       (Id(x._1.toLong) -> x._2)
     })
   }
-}
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/RestService.scala b/src/main/scala/de/retest/guistatemachine/rest/RestService.scala
index c81b3a4..e73822a 100644
--- a/src/main/scala/de/retest/guistatemachine/rest/RestService.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/RestService.scala
@@ -1,31 +1,14 @@
 package de.retest.guistatemachine.rest
 
 import akka.actor.ActorSystem
-import akka.http.scaladsl.Http
-import akka.stream.ActorMaterializer
-import akka.Done
-import akka.http.scaladsl.server.Route
-import akka.http.scaladsl.server.Directives._
-import akka.http.scaladsl.model.StatusCodes
 import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
-import spray.json.DefaultJsonProtocol._
-import spray.json._
-
-import de.retest.guistatemachine.persistence.Persistence
-import de.retest.guistatemachine.model.GuiApplications
-import de.retest.guistatemachine.model.GuiApplication
-import de.retest.guistatemachine.model.TestSuite
-import de.retest.guistatemachine.model.TestSuites
-import de.retest.guistatemachine.model.Id
+import akka.http.scaladsl.model.StatusCodes
+import akka.http.scaladsl.server.Directives._
+import akka.http.scaladsl.server.Route
+import akka.stream.ActorMaterializer
 import de.retest.guistatemachine.persistence.Persistence
-import de.retest.guistatemachine.model.StateMachine
-import de.retest.guistatemachine.model.Transition
-import de.retest.guistatemachine.model.Transitions
-import de.retest.guistatemachine.model.Action
-import de.retest.guistatemachine.model.Actions
-import de.retest.guistatemachine.model.StateMachines
-import de.retest.guistatemachine.model.State
-import de.retest.guistatemachine.model.States
+import de.retest.guistatemachine.rest.model.{Action, Actions, Id, State, StateMachine, StateMachines, States, Transition, Transitions}
+import spray.json.DefaultJsonProtocol._
 
 trait RestService {
   implicit val system: ActorSystem
@@ -47,19 +30,6 @@ trait RestService {
   implicit val idMapFormatStateMachines = new JsonFormatForIdMap[StateMachine]
   implicit val stateMachinesFormat = jsonFormat1(StateMachines)
 
-  implicit val testSuiteFormat = jsonFormat0(TestSuite)
-  implicit val idMapFormatTestSuites = new JsonFormatForIdMap[TestSuite]
-  implicit val testSuitesFormat = jsonFormat1(TestSuites)
-  implicit val applicationFormat = jsonFormat1(GuiApplication)
-  implicit val idMapFormatApplications = new JsonFormatForIdMap[GuiApplication]
-  implicit val applicationsFormat = jsonFormat1(GuiApplications)
-
-  /**
-   * Creates the complete route for the REST service with all possible paths.
-   * Note that the order of path prefixes is important.
-   * For example, if "application/LongNumber" comes before "application/LongNumber/bla", the second path
-   * will always be ignored.
-   */
   def getRoute(persistence: Persistence): Route =
     get {
       pathSingleSlash {
@@ -68,51 +38,23 @@ trait RestService {
         path("state-machines") {
           complete(persistence.getStateMachines())
         } ~
-        path("applications") {
-          complete(persistence.getApplications())
-        } ~
-        path("application" / LongNumber / "test-suites") { id =>
-          val testSuites = persistence.getTestSuites(Id(id))
-          testSuites match {
-            case Some(x) => complete(x)
-            case None => complete(StatusCodes.NotFound)
-          }
-        } ~
-        path("application" / LongNumber / "test-suite" / LongNumber) { (appId, suiteId) =>
-          val suite = persistence.getTestSuite(Id(appId), Id(suiteId))
-          suite match {
-            case Some(x) => complete(x)
-            case None => complete(StatusCodes.NotFound)
-          }
-        } ~
-        path("application" / LongNumber) { id =>
-          val app = persistence.getApplication(Id(id))
+        path("state-machine" / LongNumber) { id =>
+          val app = persistence.getStateMachine(Id(id))
           app match {
             case Some(x) => complete(x)
-            case None => complete(StatusCodes.NotFound)
+            case None    => complete(StatusCodes.NotFound)
           }
         }
     } ~
       post {
-        path("create-application") {
-          val id = persistence.addApplication()
+        path("create-state-machine") {
+          val id = persistence.createStateMachine()
           complete(id)
-        } ~
-          pathPrefix("application" / LongNumber / "create-test-suite") { appId =>
-            {
-              val id = persistence.addTestSuite(Id(appId))
-              complete(id)
-            }
-          }
-      } ~ delete {
-        path("application" / LongNumber / "test-suite" / LongNumber) { (appId, suiteId) =>
-          val r = persistence.deleteTestSuite(Id(appId), Id(suiteId))
-          complete(if (r) StatusCodes.OK else StatusCodes.NotFound)
         }
       } ~ delete {
-        path("application" / LongNumber) { id =>
-          val r = persistence.deleteApplication(Id(id))
-          complete(if (r) StatusCodes.OK else StatusCodes.NotFound)
-        }
+      path("state-machine" / LongNumber) { stateMachineId =>
+        val r = persistence.deleteStateMachine(Id(stateMachineId))
+        complete(if (r) StatusCodes.OK else StatusCodes.NotFound)
       }
+    }
 }
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/WebServer.scala b/src/main/scala/de/retest/guistatemachine/rest/WebServer.scala
index 582cfb4..625be27 100644
--- a/src/main/scala/de/retest/guistatemachine/rest/WebServer.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/WebServer.scala
@@ -1,7 +1,5 @@
 package de.retest.guistatemachine.rest
 
-import scala.io.StdIn
-
 import akka.actor.ActorSystem
 import akka.http.scaladsl.Http
 import akka.http.scaladsl.server.RouteResult.route2HandlerFlow
@@ -9,9 +7,11 @@ import akka.stream.ActorMaterializer
 import de.retest.guistatemachine.persistence.Persistence
 import scopt.OptionParser
 
+import scala.io.StdIn
+
 object WebServer extends App with RestService {
-  final val HOST = "localhost"
-  final val PORT = 8888
+  final val Host = "localhost"
+  final val Port = 8888
 
   implicit val system = ActorSystem("gui-state-machine-api-system")
   implicit val materializer = ActorMaterializer()
@@ -34,9 +34,9 @@ object WebServer extends App with RestService {
     case Some(config) =>
       val persistence = new Persistence
 
-      val bindingFuture = Http().bindAndHandle(getRoute(persistence), HOST, PORT)
+      val bindingFuture = Http().bindAndHandle(getRoute(persistence), Host, Port)
 
-      println(s"Server online at http://${HOST}:${PORT}/")
+      println(s"Server online at http://${Host}:${Port}/")
 
       if (config.maxtime < 0) {
         println("Press RETURN to stop...")
@@ -48,6 +48,5 @@ object WebServer extends App with RestService {
       bindingFuture
         .flatMap(_.unbind()) // trigger unbinding from the port
         .onComplete(_ => system.terminate()) // and shutdown when done
-    case None =>
   }
 }
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/Action.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Action.scala
new file mode 100644
index 0000000..fe5a367
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Action.scala
@@ -0,0 +1,3 @@
+package de.retest.guistatemachine.rest.model
+
+case class Action()
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/Actions.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Actions.scala
new file mode 100644
index 0000000..ef15e6c
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Actions.scala
@@ -0,0 +1,3 @@
+package de.retest.guistatemachine.rest.model
+
+case class Actions(actions: Map[Action])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Id.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Id.scala
similarity index 58%
rename from src/main/scala/de/retest/guistatemachine/model/Id.scala
rename to src/main/scala/de/retest/guistatemachine/rest/model/Id.scala
index a02f591..7c898e2 100644
--- a/src/main/scala/de/retest/guistatemachine/model/Id.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Id.scala
@@ -1,7 +1,6 @@
-package de.retest.guistatemachine.model
+package de.retest.guistatemachine.rest.model
 
 final case class Id(val id: Long) extends Ordered[Id] {
-  import scala.math.Ordered.orderingToOrdered
 
   override def compare(that: Id): Int = this.id compare that.id
 }
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/Map.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Map.scala
new file mode 100644
index 0000000..d6974db
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Map.scala
@@ -0,0 +1,42 @@
+package de.retest.guistatemachine.rest.model
+
+import scala.collection.immutable.HashMap
+
+/**
+  * This custom type allows storing values using [[Id]] as key.
+  * [[de.retest.guistatemachine.rest.JsonFormatForIdMap]] implements marshalling and unmarshalling for JSON for this type.
+  * We cannot extend immutable maps in Scala, so we have to keep it as field.
+  */
+case class Map[T](var values: scala.collection.immutable.Map[Id, T] = new HashMap[Id, T]) {
+
+  /**
+    * Generates a new ID based on the existing entries.
+    * TODO #1 Generate IDs in a better way. Maybe random numbers until one unused element is found?
+    */
+  def generateId: Id = if (values.isEmpty) Id(0) else Id(values.keySet.max.id + 1)
+  def addNewElement(v: T): Id = {
+    val generatedId = generateId
+    values = values + (generatedId -> v)
+    generatedId
+  }
+
+  def removeElement(id: Id): Boolean =
+    if (values.contains(id)) {
+      values = values - id
+      true
+    } else {
+      false
+    }
+
+  def getElement(id: Id): T = values(id)
+
+  def hasElement(id: Id): Boolean = values.contains(id)
+}
+
+object Map {
+  def fromValues[T](v: T*): Map[T] = {
+    val r = Map[T]()
+    for (e <- v) r.addNewElement(e)
+    r
+  }
+}
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/State.scala b/src/main/scala/de/retest/guistatemachine/rest/model/State.scala
new file mode 100644
index 0000000..2282f7d
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/State.scala
@@ -0,0 +1,3 @@
+package de.retest.guistatemachine.rest.model
+
+final case class State(transitions: Transitions)
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/StateMachine.scala b/src/main/scala/de/retest/guistatemachine/rest/model/StateMachine.scala
new file mode 100644
index 0000000..1706747
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/StateMachine.scala
@@ -0,0 +1,6 @@
+package de.retest.guistatemachine.rest.model
+
+/**
+ * State machine which represents a GUI test.
+ */
+final case class StateMachine(states: States = States(Map.fromValues[State](State(Transitions()))), actions: Actions = Actions(Map()))
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/StateMachines.scala b/src/main/scala/de/retest/guistatemachine/rest/model/StateMachines.scala
similarity index 59%
rename from src/main/scala/de/retest/guistatemachine/model/StateMachines.scala
rename to src/main/scala/de/retest/guistatemachine/rest/model/StateMachines.scala
index c88252d..c48c492 100644
--- a/src/main/scala/de/retest/guistatemachine/model/StateMachines.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/StateMachines.scala
@@ -1,3 +1,3 @@
-package de.retest.guistatemachine.model
+package de.retest.guistatemachine.rest.model
 
 final case class StateMachines(stateMachines: Map[StateMachine])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/States.scala b/src/main/scala/de/retest/guistatemachine/rest/model/States.scala
new file mode 100644
index 0000000..9f18dc9
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/States.scala
@@ -0,0 +1,3 @@
+package de.retest.guistatemachine.rest.model
+
+case class States(states: Map[State])
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/model/Transition.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Transition.scala
similarity index 52%
rename from src/main/scala/de/retest/guistatemachine/model/Transition.scala
rename to src/main/scala/de/retest/guistatemachine/rest/model/Transition.scala
index 930e10a..4e3965a 100644
--- a/src/main/scala/de/retest/guistatemachine/model/Transition.scala
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Transition.scala
@@ -1,3 +1,3 @@
-package de.retest.guistatemachine.model
+package de.retest.guistatemachine.rest.model
 
 final case class Transition(to : Id, action : Id)
\ No newline at end of file
diff --git a/src/main/scala/de/retest/guistatemachine/rest/model/Transitions.scala b/src/main/scala/de/retest/guistatemachine/rest/model/Transitions.scala
new file mode 100644
index 0000000..54da2ad
--- /dev/null
+++ b/src/main/scala/de/retest/guistatemachine/rest/model/Transitions.scala
@@ -0,0 +1,3 @@
+package de.retest.guistatemachine.rest.model
+
+final case class Transitions(transitions: Map[Transition] = Map())
\ No newline at end of file
diff --git a/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImplSpec.scala b/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImplSpec.scala
new file mode 100644
index 0000000..4329219
--- /dev/null
+++ b/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineApiImplSpec.scala
@@ -0,0 +1,19 @@
+package de.retest.guistatemachine.api.impl
+
+import de.retest.guistatemachine.api.{AbstractApiSpec, GuiStateMachine}
+
+class GuiStateMachineApiImplSpec extends AbstractApiSpec {
+
+  var stateMachine: GuiStateMachine = null
+
+  "GuiStateMachineApi" should {
+    "create a new state machine" in {
+      stateMachine = GuiStateMachineApiImpl.createStateMachine
+      stateMachine should not be null
+    }
+
+    "remove a state machine" in {
+      GuiStateMachineApiImpl.removeStateMachine(stateMachine) shouldBe true
+    }
+  }
+}
\ No newline at end of file
diff --git a/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImplSpec.scala b/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImplSpec.scala
index 9367088..ed4fa45 100644
--- a/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImplSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/api/impl/GuiStateMachineImplSpec.scala
@@ -4,6 +4,7 @@ import de.retest.guistatemachine.api.{AbstractApiSpec, Action, Descriptors}
 
 class GuiStateMachineImplSpec extends AbstractApiSpec {
 
+  val sut = new GuiStateMachineImpl
   val rootElementA = getRootElement("a")
   val rootElementB = getRootElement("b")
   val action0Mock = getAction()
@@ -11,22 +12,34 @@ class GuiStateMachineImplSpec extends AbstractApiSpec {
 
   "GuiStateMachine" should {
     "get an initial state" in {
-      val initial = GuiStateMachineImpl.getState(getDescriptors, getNeverExploredActions)
+      val initial = sut.getState(getDescriptors, getNeverExploredActions)
       initial.getNeverExploredActions.size shouldEqual 2
       initial.getTransitions.size shouldEqual 0
     }
 
-    "add a transition to a new state" in {
+    "add two transitions to two new states for the same action" in {
       val initialDescriptors = getDescriptors
-      val initial = GuiStateMachineImpl.getState(getDescriptors, getNeverExploredActions)
-      val sDescriptors = Descriptors(Set(rootElementA))
+      val initial = sut.getState(getDescriptors, getNeverExploredActions)
+
+      val s0Descriptors = Descriptors(Set(rootElementA))
+      // It should be a new state and not the same again.
+      initialDescriptors.equals(s0Descriptors) shouldEqual false
+      val s0 = sut.executeAction(initial, Action(action0Mock), s0Descriptors, getNeverExploredActions)
+      initial.getNeverExploredActions.size shouldEqual 1
+      initial.getTransitions.size shouldEqual 1
+      initial.getTransitions(Action(action0Mock)).size shouldEqual 1
+      s0.getNeverExploredActions.size shouldEqual 2
+      s0.getTransitions.size shouldEqual 0
+
+      val s1Descriptors = Descriptors(Set(rootElementB))
       // It should be a new state and not the same again.
-      initialDescriptors.equals(sDescriptors) shouldEqual false
-      val s = GuiStateMachineImpl.executeAction(initial, Action(action0Mock), sDescriptors, getNeverExploredActions)
+      initialDescriptors.equals(s1Descriptors) shouldEqual false
+      val s1 = sut.executeAction(initial, Action(action0Mock), s1Descriptors, getNeverExploredActions)
       initial.getNeverExploredActions.size shouldEqual 1
       initial.getTransitions.size shouldEqual 1
-      s.getNeverExploredActions.size shouldEqual 2
-      s.getTransitions.size shouldEqual 0
+      initial.getTransitions(Action(action0Mock)).size shouldEqual 2
+      s1.getNeverExploredActions.size shouldEqual 2
+      s1.getTransitions.size shouldEqual 0
     }
   }
 
diff --git a/src/test/scala/de/retest/guistatemachine/api/impl/StateImplSpec.scala b/src/test/scala/de/retest/guistatemachine/api/impl/StateImplSpec.scala
index 8179c32..4efb196 100644
--- a/src/test/scala/de/retest/guistatemachine/api/impl/StateImplSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/api/impl/StateImplSpec.scala
@@ -1,4 +1,5 @@
 package de.retest.guistatemachine.api.impl
+
 import de.retest.guistatemachine.api.{AbstractApiSpec, Action, Descriptors}
 
 import scala.collection.immutable.HashSet
@@ -15,6 +16,7 @@ class StateImplSpec extends AbstractApiSpec {
       val s0 = new StateImpl(descriptorsA, HashSet(Action(action0Mock)))
       val s1 = new StateImpl(descriptorsB, HashSet(Action(action1Mock)))
       s0.equals(s1) shouldEqual false
+      s0.equals(null) shouldEqual false
     }
 
     "equal" in {
@@ -22,5 +24,10 @@ class StateImplSpec extends AbstractApiSpec {
       val s1 = new StateImpl(descriptorsA, HashSet(Action(action1Mock)))
       s0.equals(s1) shouldEqual true
     }
+
+    "be converted into a string" in {
+      val s0 = new StateImpl(descriptorsA, HashSet(Action(action0Mock)))
+      s0.toString shouldEqual "descriptors=Descriptors(Set()),neverExploredActions=Set(Selenium Action),transitions=Map()"
+    }
   }
 }
diff --git a/src/test/scala/de/retest/guistatemachine/dsl/StateMachinesSpec.scala b/src/test/scala/de/retest/guistatemachine/dsl/StateMachinesSpec.scala
deleted file mode 100644
index 142577e..0000000
--- a/src/test/scala/de/retest/guistatemachine/dsl/StateMachinesSpec.scala
+++ /dev/null
@@ -1,57 +0,0 @@
-package de.retest.guistatemachine.dsl
-
-import org.scalatest.WordSpec
-import org.scalatest.Matchers
-
-/**
- * Tests the construction of state machines with the DSL.
- */
-class StateMachinesSpec extends WordSpec with Matchers {
-
-  "StateMachines" should {
-    "be constructed as NFAs from objects" in {
-      case object Start0 extends InitialState
-      case object S0_0 extends State
-      case object S0_1 extends State
-      case object End0 extends FinalState
-
-      case object Start1 extends InitialState
-      case object S1_0 extends State
-      case object S1_1 extends State
-      case object End1 extends FinalState
-
-      case object EnterText extends Action
-      case object PressExitButton extends Action
-
-      val r = StateMachines {
-        StateMachine {
-          Start0 - EnterText - S0_0
-          Start0 - EnterText - S0_1
-          S0_0 - PressExitButton - End0
-          S0_1 - PressExitButton - End0
-        } ~
-          StateMachine {
-            Start1 - EnterText - S1_0
-            Start1 - EnterText - S1_1
-            S1_0 - PressExitButton - End1
-            S1_1 - PressExitButton - End1
-          }
-      }
-
-      r.size shouldEqual 2
-      val stateMachine0 = r(0)
-
-      val initial0 = stateMachine0.getInitial
-      initial0 should be theSameInstanceAs Start0
-      initial0.getTransitions.size shouldEqual 2
-
-      val initial0Trans0 = initial0.getTransitions(0)
-      initial0Trans0.getAction should be theSameInstanceAs EnterText
-      initial0Trans0.getTo should be theSameInstanceAs S0_0
-
-      val initial0Trans1 = initial0.getTransitions(1)
-      initial0Trans1.getAction should be theSameInstanceAs EnterText
-      initial0Trans1.getTo should be theSameInstanceAs S0_1
-    }
-  }
-}
\ No newline at end of file
diff --git a/src/test/scala/de/retest/guistatemachine/persistence/PersistenceSpec.scala b/src/test/scala/de/retest/guistatemachine/persistence/PersistenceSpec.scala
deleted file mode 100644
index 27168a8..0000000
--- a/src/test/scala/de/retest/guistatemachine/persistence/PersistenceSpec.scala
+++ /dev/null
@@ -1,22 +0,0 @@
-package de.retest.guistatemachine.persistence
-
-import org.scalatest.Matchers
-import org.scalatest.WordSpec
-import de.retest.guistatemachine.model.Id
-
-class PersistenceSpec extends WordSpec with Matchers {
-  val sut = new Persistence
-
-  "The pesistence" should {
-    "allow adding one test suite" in {
-      sut.getApplications().apps.values.size shouldEqual 0
-      sut.addApplication().id shouldEqual 0
-      sut.getApplications().apps.values.size shouldEqual 1
-      sut.getTestSuites(Id(0)).get.suites.values.size shouldEqual 0
-      sut.addTestSuite(Id(0)).get.id shouldEqual 0
-      sut.getTestSuites(Id(0)).get.suites.values.size shouldEqual 1
-      val s = sut.getTestSuite(Id(0), Id(0))
-      s.isEmpty shouldEqual false
-    }
-  }
-}
\ No newline at end of file
diff --git a/src/test/scala/de/retest/guistatemachine/rest/JsonFormatForIdMapSpec.scala b/src/test/scala/de/retest/guistatemachine/rest/JsonFormatForIdMapSpec.scala
index f6ac8d8..f2bed4d 100644
--- a/src/test/scala/de/retest/guistatemachine/rest/JsonFormatForIdMapSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/rest/JsonFormatForIdMapSpec.scala
@@ -1,65 +1,37 @@
 package de.retest.guistatemachine.rest
 
-import org.scalatest.WordSpec
-import org.scalatest.Matchers
-
-import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
+import de.retest.guistatemachine.rest.model.{Action, Actions, Id}
+import org.scalatest.{Matchers, WordSpec}
 import spray.json.DefaultJsonProtocol._
 import spray.json._
-import de.retest.guistatemachine.model.TestSuites
-import de.retest.guistatemachine.model.Id
-import de.retest.guistatemachine.model.TestSuite
+
 import scala.collection.immutable.HashMap
-import de.retest.guistatemachine.model.Map
-import de.retest.guistatemachine.model.GuiApplications
-import de.retest.guistatemachine.model.GuiApplication
 
 class JsonFormatForIdMapSpec extends WordSpec with Matchers {
-
   implicit val idFormat = jsonFormat1(Id)
-  implicit val testSuiteFormat = jsonFormat0(TestSuite)
-  implicit val hashMapFormatTestSuites = new JsonFormatForIdMap[TestSuite]
-  implicit val testSuitesFormat = jsonFormat1(TestSuites)
-  implicit val applicationFormat = jsonFormat1(GuiApplication)
-  implicit val hashMapFormatApplications = new JsonFormatForIdMap[GuiApplication]
-  implicit val applicationsFormat = jsonFormat1(GuiApplications)
 
-  "The JSON format" should {
-    "convert an empty test suite into JSON and back" in {
-      val testSuites = TestSuites(Map(new HashMap[Id, TestSuite]()))
-      val json = testSuites.toJson
-      json.toString shouldEqual "{\"suites\":{}}"
-      val transformedTestSuites = json.convertTo[TestSuites]
-      transformedTestSuites.suites.values.isEmpty shouldEqual true
-    }
+  implicit val actionFormat = jsonFormat0(Action)
+  implicit val idMapFormatActions = new JsonFormatForIdMap[Action]
+  implicit val actionsFormat = jsonFormat1(Actions)
 
-    "convert a test suite with elements into JSON and back" in {
-      val testSuites = TestSuites(Map(new HashMap[Id, TestSuite]()))
-      testSuites.suites.values = testSuites.suites.values + (Id(0) -> TestSuite())
-      val json = testSuites.toJson
-      json.toString shouldEqual "{\"suites\":{\"0\":{}}}"
-      val transformedTestSuites = json.convertTo[TestSuites]
-      transformedTestSuites.suites.values.isEmpty shouldEqual false
-      transformedTestSuites.suites.values.contains(Id(0)) shouldEqual true
+  "The JSON format" should {
+    "convert empty actions into JSON and back" in {
+      val actions = model.Actions(model.Map(new HashMap[Id, Action]()))
+      val json = actions.toJson
+      json.toString shouldEqual "{\"actions\":{}}"
+      val transformedActions = json.convertTo[Actions]
+      transformedActions.actions.values.isEmpty shouldEqual true
     }
 
-    /**
-     * Tests nested fields which do both contain a Map.
-     */
-    "convert an application into JSON and back" in {
-      val testSuites = TestSuites(Map(new HashMap[Id, TestSuite]()))
-      testSuites.suites.values = testSuites.suites.values + (Id(0) -> TestSuite())
-      val apps = GuiApplications(Map(new HashMap[Id, GuiApplication]()))
-      apps.apps.values = apps.apps.values + (Id(0) -> new GuiApplication(testSuites))
-      val json = apps.toJson
-      json.toString shouldEqual "{\"apps\":{\"0\":{\"testSuites\":{\"suites\":{\"0\":{}}}}}}"
-      val transformedApps = json.convertTo[GuiApplications]
-      transformedApps.apps.values.isEmpty shouldEqual false
-      transformedApps.apps.values.contains(Id(0)) shouldEqual true
-      val transformedSuites = transformedApps.apps.values(Id(0)).testSuites.suites.values
-      transformedSuites.isEmpty shouldEqual false
-      transformedSuites.contains(Id(0)) shouldEqual true
+    "convert actions with elements into JSON and back" in {
+      val actions = model.Actions(model.Map(new HashMap[Id, Action]()))
+      actions.actions.values = actions.actions.values + (Id(0) -> Action())
+      val json = actions.toJson
+      json.toString shouldEqual "{\"actions\":{\"0\":{}}}"
+      val transformedActions = json.convertTo[Actions]
+      transformedActions.actions.values.isEmpty shouldEqual false
+      transformedActions.actions.values.contains(Id(0)) shouldEqual true
     }
   }
 
-}
\ No newline at end of file
+}
diff --git a/src/test/scala/de/retest/guistatemachine/rest/RestServiceSpec.scala b/src/test/scala/de/retest/guistatemachine/rest/RestServiceSpec.scala
index fcce136..6a585de 100644
--- a/src/test/scala/de/retest/guistatemachine/rest/RestServiceSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/rest/RestServiceSpec.scala
@@ -1,23 +1,10 @@
 package de.retest.guistatemachine.rest
 
-import org.scalatest.{ Matchers, WordSpec }
-import akka.http.scaladsl.model.StatusCodes
-import akka.http.scaladsl.testkit.ScalatestRouteTest
-import akka.http.scaladsl.server._
-import Directives._
-import akka.http.scaladsl.model.HttpEntity
-import akka.http.scaladsl.model.ContentTypes
-import akka.http.scaladsl.model.HttpCharset
 import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport._
-import de.retest.guistatemachine.model.GuiApplications
-import de.retest.guistatemachine.model.Id
-import de.retest.guistatemachine.model.GuiApplication
-import de.retest.guistatemachine.model.TestSuites
+import akka.http.scaladsl.model.{MediaTypes, StatusCodes}
+import akka.http.scaladsl.testkit.ScalatestRouteTest
 import de.retest.guistatemachine.persistence.Persistence
-import akka.http.scaladsl.model.MediaType
-import akka.http.scaladsl.model.MediaTypes
-import de.retest.guistatemachine.model.TestSuite
-import akka.http.scaladsl.model.StatusCode
+import org.scalatest.{Matchers, WordSpec}
 
 class RestServiceSpec extends WordSpec with Matchers with ScalatestRouteTest with RestService {
 
@@ -33,113 +20,61 @@ class RestServiceSpec extends WordSpec with Matchers with ScalatestRouteTest wit
       }
     }
 
-    "return an empty list for the GET request with the path /applications" in {
-      Get("/applications") ~> sut ~> check {
+    "return an empty list for the GET request with the path /state-machines" in {
+      Get("/state-machines") ~> sut ~> check {
+        import de.retest.guistatemachine.rest.model.StateMachines
         handled shouldEqual true
         mediaType shouldEqual MediaTypes.`application/json`
-        val r = responseAs[GuiApplications]
-        r.apps.values.size shouldEqual 0
-      }
-    }
-
-    "fail for the GET request with the path /application/0" in {
-      Get("/application/0") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.NotFound
-      }
-    }
-
-    "fail for the DELETE request with the path /application/0" in {
-      Delete("/application/0") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.NotFound
-      }
-    }
-
-    "fail for the GET request with the path /application/0/test-suites" in {
-      Get("/application/0/test-suites") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.NotFound
-      }
-    }
-
-    "allow POST for path /create-application" in {
-      Post("/create-application") ~> sut ~> check {
-        handled shouldEqual true
-        responseAs[Id] shouldEqual Id(0)
-        persistence.getApplications.apps.values.size shouldEqual 1
-      }
-    }
-
-    "return an empty application for the GET request with the path /application/0" in {
-      Get("/application/0") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.OK
-        val r = responseAs[GuiApplication]
-        r.testSuites.suites.values.size shouldEqual 0
+        val r = responseAs[StateMachines]
+        r.stateMachines.values.size shouldEqual 0
       }
     }
 
-    "return an empty list for the GET request with the path /application/0/test-suites" in {
-      Get("/application/0/test-suites") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.OK
-        val r = responseAs[TestSuites]
-        r.suites.values.size shouldEqual 0
-      }
-    }
-
-    "fail for the GET request with the path /application/0/test-suite/0" in {
-      Get("/application/0/test-suite/0") ~> sut ~> check {
+    "fail for the GET request with the path /state-machine/0" in {
+      Get("/state-machine/0") ~> sut ~> check {
         handled shouldEqual true
         status shouldEqual StatusCodes.NotFound
       }
     }
 
-    "fail for the DELETE request with the path /application/0/test-suite/0" in {
-      Delete("/application/0/test-suite/0") ~> sut ~> check {
+    "fail for the DELETE request with the path /state-machine/0" in {
+      Delete("/state-machine/0") ~> sut ~> check {
         handled shouldEqual true
         status shouldEqual StatusCodes.NotFound
       }
     }
 
-    "allow POST for path /application/0/create-test-suite" in {
-      Post("/application/0/create-test-suite") ~> sut ~> check {
+    "allow POST for path /create-state-machine" in {
+      Post("/create-state-machine") ~> sut ~> check {
+        import de.retest.guistatemachine.rest.model.Id
         handled shouldEqual true
         responseAs[Id] shouldEqual Id(0)
-        persistence.getTestSuites(Id(0)).get.suites.values.size shouldEqual 1
+        persistence.getStateMachines().stateMachines.values.size shouldEqual 1
       }
     }
 
-    "return an empty test suite for the GET request with the path /application/0/test-suite/0" in {
-      Get("/application/0/test-suite/0") ~> sut ~> check {
+    "return an empty application for the GET request with the path /state-machine/0" in {
+      Get("/state-machine/0") ~> sut ~> check {
+        import de.retest.guistatemachine.rest.model.StateMachine
         handled shouldEqual true
         status shouldEqual StatusCodes.OK
-        val r = responseAs[TestSuite]
-        // TODO There is no content in a test suite at the moment
-      }
-    }
-
-    "return status OK for the DELETE request with the path /application/0/test-suite/0" in {
-      Delete("/application/0/test-suite/0") ~> sut ~> check {
-        handled shouldEqual true
-        status shouldEqual StatusCodes.OK
-        responseAs[String] shouldEqual "OK"
-        persistence.getTestSuites(Id(0)).get.suites.values.size shouldEqual 0
+        val r = responseAs[StateMachine]
+        r.states.states.values.size shouldEqual 1
+        r.actions.actions.values.size shouldEqual 0
       }
     }
 
-    "return status OK for the DELETE request with the path /application/0" in {
-      Delete("/application/0") ~> sut ~> check {
+    "return status OK for the DELETE request with the path /state-machine/0" in {
+      Delete("/state-machine/0") ~> sut ~> check {
         handled shouldEqual true
         status shouldEqual StatusCodes.OK
         responseAs[String] shouldEqual "OK"
-        persistence.getApplications().apps.values.size shouldEqual 0
+        persistence.getStateMachines().stateMachines.values.size shouldEqual 0
       }
     }
 
-    "not handle the GET request with the path /applications/bla/hello/bla" in {
-      Get("/applications/bla/hello/bla") ~> sut ~> check {
+    "not handle the GET request with the path /state-machines/bla/hello/bla" in {
+      Get("/state-machines/bla/hello/bla") ~> sut ~> check {
         handled shouldEqual false
         //mediaType shouldEqual MediaTypes.`application/json`
         //val r = responseAs[GuiApplications]
diff --git a/src/test/scala/de/retest/guistatemachine/rest/WebServerSpec.scala b/src/test/scala/de/retest/guistatemachine/rest/WebServerSpec.scala
index 34b5af5..77c9f26 100644
--- a/src/test/scala/de/retest/guistatemachine/rest/WebServerSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/rest/WebServerSpec.scala
@@ -1,13 +1,14 @@
 package de.retest.guistatemachine.rest
 
-import org.scalatest.Matchers
-import org.scalatest.WordSpec
+import org.scalatest.{Matchers, WordSpec}
 
 class WebServerSpec extends WordSpec with Matchers {
 
   "The web server" should {
     "start and end successfully" in {
+      WebServer.Host shouldEqual "localhost"
+      WebServer.Port shouldEqual 8888
       WebServer.main(Array("--maxtime=1000"))
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/test/scala/de/retest/guistatemachine/model/IdSpec.scala b/src/test/scala/de/retest/guistatemachine/rest/model/IdSpec.scala
similarity index 71%
rename from src/test/scala/de/retest/guistatemachine/model/IdSpec.scala
rename to src/test/scala/de/retest/guistatemachine/rest/model/IdSpec.scala
index 8b7d110..a0bc895 100644
--- a/src/test/scala/de/retest/guistatemachine/model/IdSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/rest/model/IdSpec.scala
@@ -1,7 +1,6 @@
-package de.retest.guistatemachine.model
+package de.retest.guistatemachine.rest.model
 
-import org.scalatest.WordSpec
-import org.scalatest.Matchers
+import org.scalatest.{Matchers, WordSpec}
 
 class IdSpec extends WordSpec with Matchers {
 
@@ -14,4 +13,4 @@ class IdSpec extends WordSpec with Matchers {
       id1.compare(id0) shouldEqual 1
     }
   }
-}
\ No newline at end of file
+}
diff --git a/src/test/scala/de/retest/guistatemachine/model/MapSpec.scala b/src/test/scala/de/retest/guistatemachine/rest/model/MapSpec.scala
similarity index 78%
rename from src/test/scala/de/retest/guistatemachine/model/MapSpec.scala
rename to src/test/scala/de/retest/guistatemachine/rest/model/MapSpec.scala
index 2ba7cbb..6d990eb 100644
--- a/src/test/scala/de/retest/guistatemachine/model/MapSpec.scala
+++ b/src/test/scala/de/retest/guistatemachine/rest/model/MapSpec.scala
@@ -1,7 +1,7 @@
-package de.retest.guistatemachine.model
+package de.retest.guistatemachine.rest.model
+
+import org.scalatest.{Matchers, WordSpec}
 
-import org.scalatest.WordSpec
-import org.scalatest.Matchers
 import scala.collection.immutable.HashMap
 
 class MapSpec extends WordSpec with Matchers {
@@ -17,4 +17,4 @@ class MapSpec extends WordSpec with Matchers {
       id1.id shouldEqual 1
     }
   }
-}
\ No newline at end of file
+}