Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb
===================================================================
diff -u -r1726 -r1730
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb	(.../Employee.vb)	(revision 1726)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/Employee.vb	(.../Employee.vb)	(revision 1730)
@@ -20,4 +20,7 @@
         Return employee.Initials.Equals(Initials, StringComparison.CurrentCultureIgnoreCase)
     End Function
 
+    Public overrides Function ToString() As String Implements IEmployee.ToString
+        Return $"Employee: {FirstName} {LastName} ({Initials})"
+    End Function
 End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityFinishedState.vb	(revision 1730)
@@ -0,0 +1,24 @@
+Imports ActiviteitenOpvolging
+
+Public Class ActivityFinishedState
+    Inherits ActivityState
+
+    Private ReadOnly _employee As IEmployee
+
+    'Not from other state.
+    Public Sub New(activity As IActivity, employee As IEmployee)
+        Me.Activity = activity
+        _employee = employee
+    End Sub
+
+    'From other state.
+    Public Sub New(state As ActivityState)
+        Activity = state.Activity
+        _employee = state.GetEmployee()
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Function ActivityStateEnum() As ActivityStateEnum
+        Return ActiviteitenOpvolging.ActivityStateEnum.Finished
+    End Function
+End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb
===================================================================
diff -u -r1729 -r1730
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(.../ActivityStartedState.vb)	(revision 1729)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStartedState.vb	(.../ActivityStartedState.vb)	(revision 1730)
@@ -1,5 +1,5 @@
 Public Class ActivityStartedState
-    inherits ActivityState
+    Inherits ActivityState
 
     Private ReadOnly _employee As IEmployee
 
@@ -24,4 +24,22 @@
     Public Overrides Function GetEmployee() As IEmployee
         Return _employee
     End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Sub StopActivity(employee As IEmployee)
+        if Not _employee.Equals(employee) Then
+            'Different employee.
+            throw New Exception($"A different employee can't stop a started activity. Current activity belongs to {employee.ToString()}")
+        End If
+        Activity.State = New ActivityStoppedState(Me)
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Sub FinishActivity(employee As IEmployee)
+        if Not _employee.Equals(employee) Then
+            'Different employee.
+            throw New Exception($"A different employee can't finish a started activity. Current activity belongs to {employee.ToString()}")
+        End If
+        Activity.State = New ActivityFinishedState(Me)
+    End Sub
 End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb
===================================================================
diff -u
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb	(revision 0)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/implementations/activity state/ActivityStoppedState.vb	(revision 1730)
@@ -0,0 +1,33 @@
+Public Class ActivityStoppedState
+    inherits ActivityState
+
+    Private ReadOnly _employee As IEmployee
+
+    'Not from other state.
+    Public Sub New(activity As IActivity, employee As IEmployee)
+        Me.Activity = activity
+        _employee = employee
+    End Sub
+
+    'From other state.
+    Public Sub New(state As ActivityState)
+        Activity = state.Activity
+        _employee = state.GetEmployee()
+    End Sub
+
+    ''' <inheritdoc/>
+    Public Overrides Function ActivityStateEnum() As ActivityStateEnum
+        Return ActiviteitenOpvolging.ActivityStateEnum.Stopped
+    End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Function GetEmployee() As IEmployee
+        Return _employee
+    End Function
+
+    ''' <inheritdoc/>
+    Public Overrides Sub StartActivity(employee As IEmployee)
+        'Everyone can start this activity.
+        Activity.State = New ActivityStartedState(Me, employee)
+    End Sub
+End Class
Index: ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb
===================================================================
diff -u -r1726 -r1730
--- ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb	(.../IEmployee.vb)	(revision 1726)
+++ ActiviteitenOpvolging/ActiviteitenOpvolging/domain/classes/IEmployee.vb	(.../IEmployee.vb)	(revision 1730)
@@ -8,4 +8,5 @@
     Property CurrentActivity As IActivity
 
     Function Equals(obj As Object) As Boolean
+    Function ToString() As String
 End Interface