Continued scaffolding:

- Implemented basic logging
- Added basic settings
- Moved contracts to separate assembly

SafeExamBrowser.Contracts/Configuration/ISettings.cs

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+namespace SafeExamBrowser.Contracts.Configuration
+{
+	public interface ISettings
+	{
+		string LogFolderPath { get; }
+	}
+}

SafeExamBrowser.Contracts/I18n/IText.cs

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+namespace SafeExamBrowser.Contracts.I18n
+{
+	public interface IText
+	{
+		string Get(Key key);
+	}
+}

SafeExamBrowser.Contracts/I18n/ITextResource.cs

@@ -7,9 +7,8 @@
  */
 
 using System.Collections.Generic;
-using SafeExamBrowser.Core.I18n;
 
-namespace SafeExamBrowser.Core.Contracts
+namespace SafeExamBrowser.Contracts.I18n
 {
 	public interface ITextResource
 	{

SafeExamBrowser.Contracts/I18n/Key.cs

@@ -6,11 +6,10 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-namespace SafeExamBrowser.Core.I18n
+namespace SafeExamBrowser.Contracts.I18n
 {
 	public enum Key
 	{
-		MessageBox_FatalErrorTitle,
 		MessageBox_SingleInstance,
 		MessageBox_SingleInstanceTitle
 	}

SafeExamBrowser.Contracts/Logging/ILogMessage.cs

@@ -6,16 +6,14 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-using System.Collections.Generic;
+using System;
-using SafeExamBrowser.Core.Contracts;
 
-namespace SafeExamBrowser.Core.I18n
+namespace SafeExamBrowser.Contracts.Logging
 {
-	class NullTextResource : ITextResource
+	public interface ILogMessage : ICloneable
 	{
-		public IDictionary<Key, string> LoadText()
+		DateTime DateTime { get; }
-		{
+		LogLevel Severity { get; }
-			return new Dictionary<Key, string>();
+		string Message { get; }
-		}
 	}
 }

SafeExamBrowser.Contracts/Logging/ILogObserver.cs

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+namespace SafeExamBrowser.Contracts.Logging
+{
+	public interface ILogObserver
+	{
+		void Notify(ILogMessage message);
+	}
+}

SafeExamBrowser.Contracts/Logging/ILogger.cs

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System.Collections.Generic;
+
+namespace SafeExamBrowser.Contracts.Logging
+{
+	public interface ILogger
+	{
+		void Info(string message);
+		void Warn(string message);
+		void Error(string message);
+		void Subscribe(ILogObserver observer);
+		void Unsubscribe(ILogObserver observer);
+		IList<ILogMessage> GetLog();
+	}
+}

SafeExamBrowser.Contracts/Logging/LogLevel.cs

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+namespace SafeExamBrowser.Contracts.Logging
+{
+	public enum LogLevel
+	{
+		Info = 1,
+		Warn = 2,
+		Error = 3
+	}
+}

SafeExamBrowser.Contracts/Properties/AssemblyInfo.cs

@@ -0,0 +1,36 @@
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+// General Information about an assembly is controlled through the following
+// set of attributes. Change these attribute values to modify the information
+// associated with an assembly.
+[assembly: AssemblyTitle("SafeExamBrowser.Contracts")]
+[assembly: AssemblyDescription("")]
+[assembly: AssemblyConfiguration("")]
+[assembly: AssemblyCompany("")]
+[assembly: AssemblyProduct("SafeExamBrowser.Contracts")]
+[assembly: AssemblyCopyright("Copyright ©  2017")]
+[assembly: AssemblyTrademark("")]
+[assembly: AssemblyCulture("")]
+
+// Setting ComVisible to false makes the types in this assembly not visible
+// to COM components.  If you need to access a type in this assembly from
+// COM, set the ComVisible attribute to true on that type.
+[assembly: ComVisible(false)]
+
+// The following GUID is for the ID of the typelib if this project is exposed to COM
+[assembly: Guid("47da5933-bef8-4729-94e6-abde2db12262")]
+
+// Version information for an assembly consists of the following four values:
+//
+//      Major Version
+//      Minor Version
+//      Build Number
+//      Revision
+//
+// You can specify all the values or you can default the Build and Revision Numbers
+// by using the '*' as shown below:
+// [assembly: AssemblyVersion("1.0.*")]
+[assembly: AssemblyVersion("1.0.0.0")]
+[assembly: AssemblyFileVersion("1.0.0.0")]

SafeExamBrowser.Contracts/SafeExamBrowser.Contracts.csproj

@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{47DA5933-BEF8-4729-94E6-ABDE2DB12262}</ProjectGuid>
+    <OutputType>Library</OutputType>
+    <AppDesignerFolder>Properties</AppDesignerFolder>
+    <RootNamespace>SafeExamBrowser.Contracts</RootNamespace>
+    <AssemblyName>SafeExamBrowser.Contracts</AssemblyName>
+    <TargetFrameworkVersion>v4.5.2</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="Configuration\ISettings.cs" />
+    <Compile Include="I18n\IText.cs" />
+    <Compile Include="I18n\Key.cs" />
+    <Compile Include="Logging\ILogger.cs" />
+    <Compile Include="Logging\ILogMessage.cs" />
+    <Compile Include="Logging\ILogObserver.cs" />
+    <Compile Include="Logging\LogLevel.cs" />
+    <Compile Include="UserInterface\ITaskbar.cs" />
+    <Compile Include="I18n\ITextResource.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>

SafeExamBrowser.Contracts/UserInterface/ITaskbar.cs

@@ -6,7 +6,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-namespace SafeExamBrowser.Core.Contracts
+namespace SafeExamBrowser.Contracts.UserInterface
 {
 	public interface ITaskbar
 	{

SafeExamBrowser.Core.UnitTests/I18n/TextTests.cs

@@ -7,35 +7,30 @@
  */
 
 using System;
+using System.Collections.Generic;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+using SafeExamBrowser.Contracts.I18n;
 using SafeExamBrowser.Core.I18n;
 
-namespace SafeExamBrowser.Core.UnitTests
+namespace SafeExamBrowser.Core.UnitTests.I18n
 {
 	[TestClass]
 	public class TextTests
 	{
-		[TestMethod]
-		public void MustNeverBeNull()
-		{
-			Assert.IsNotNull(Text.Instance);
-		}
-
 		[TestMethod]
 		public void MustNeverReturnNull()
 		{
-			var text = Text.Instance.Get((Key) (-1));
+			var resource = new Mock<ITextResource>();
+			var sut = new Text(resource.Object);
+
+			resource.Setup(r => r.LoadText()).Returns<IDictionary<Key, string>>(null);
+
+			var text = sut.Get((Key)(-1));
 
 			Assert.IsNotNull(text);
 		}
 
-		[TestMethod]
-		[ExpectedException(typeof(ArgumentNullException))]
-		public void MustNotAllowBeingNull()
-		{
-			Text.Instance = null;
-		}
-
 		[TestMethod]
 		[ExpectedException(typeof(ArgumentNullException))]
 		public void MustNotAllowNullResource()

SafeExamBrowser.Core.UnitTests/Logging/LoggerTests.cs

@@ -0,0 +1,152 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+using System.Collections.Generic;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
+using SafeExamBrowser.Contracts.Logging;
+using SafeExamBrowser.Core.Logging;
+
+namespace SafeExamBrowser.Core.UnitTests.Logging
+{
+	[TestClass]
+	public class LoggerTests
+	{
+		[TestMethod]
+		public void MustAddMessagesToLog()
+		{
+			var sut = new Logger();
+			var info = "I'm an info message";
+			var warn = "I'm a warning!";
+			var error = "I AM AN ERROR!!";
+
+			sut.Info(info);
+			sut.Warn(warn);
+			sut.Error(error);
+
+			var log = sut.GetLog();
+
+			Assert.IsTrue(log.Count == 3);
+
+			Assert.IsTrue(info.Equals(log[0].Message));
+			Assert.IsTrue(log[0].Severity == LogLevel.Info);
+
+			Assert.IsTrue(warn.Equals(log[1].Message));
+			Assert.IsTrue(log[1].Severity == LogLevel.Warn);
+
+			Assert.IsTrue(error.Equals(log[2].Message));
+			Assert.IsTrue(log[2].Severity == LogLevel.Error);
+		}
+
+		[TestMethod]
+		public void MustReturnCopyOfLog()
+		{
+			var sut = new Logger();
+			var info = "I'm an info message";
+			var warn = "I'm a warning!";
+			var error = "I AM AN ERROR!!";
+
+			sut.Info(info);
+			sut.Warn(warn);
+			sut.Error(error);
+
+			var log1 = sut.GetLog();
+			var log2 = sut.GetLog();
+
+			Assert.AreNotSame(log1, log2);
+
+			foreach (var message in log1)
+			{
+				Assert.AreNotSame(message, log2[log1.IndexOf(message)]);
+			}
+		}
+
+		[TestMethod]
+		[ExpectedException(typeof(ArgumentNullException))]
+		public void MustNotAllowNullObserver()
+		{
+			var sut = new Logger();
+
+			sut.Subscribe(null);
+		}
+
+		[TestMethod]
+		public void MustNotSubscribeSameObserverMultipleTimes()
+		{
+			var sut = new Logger();
+			var observer = new Mock<ILogObserver>();
+
+			observer.Setup(o => o.Notify(It.IsAny<ILogMessage>()));
+
+			sut.Subscribe(observer.Object);
+			sut.Subscribe(observer.Object);
+			sut.Subscribe(observer.Object);
+
+			sut.Info("Blubb");
+
+			observer.Verify(o => o.Notify(It.IsAny<ILogMessage>()), Times.Once());
+		}
+
+		[TestMethod]
+		public void MustNotFailWhenRemovingNullObserver()
+		{
+			var sut = new Logger();
+
+			sut.Unsubscribe(null);
+		}
+
+		[TestMethod]
+		public void MustSubscribeObserver()
+		{
+			var sut = new Logger();
+			var observer = new Mock<ILogObserver>();
+			var message = "Blubb";
+			var messages = new List<ILogMessage>();
+
+			observer.Setup(o => o.Notify(It.IsAny<ILogMessage>())).Callback<ILogMessage>(m => messages.Add(m));
+
+			sut.Subscribe(observer.Object);
+			sut.Info(message);
+			sut.Warn(message);
+
+			observer.Verify(o => o.Notify(It.IsAny<ILogMessage>()), Times.Exactly(2));
+
+			Assert.IsTrue(messages.Count == 2);
+
+			Assert.IsTrue(messages[0].Severity == LogLevel.Info);
+			Assert.IsTrue(message.Equals(messages[0].Message));
+
+			Assert.IsTrue(messages[1].Severity == LogLevel.Warn);
+			Assert.IsTrue(message.Equals(messages[1].Message));
+		}
+
+		[TestMethod]
+		public void MustUnsubscribeObserver()
+		{
+			var sut = new Logger();
+			var observer = new Mock<ILogObserver>();
+			var message = "Blubb";
+			var messages = new List<ILogMessage>();
+
+			observer.Setup(o => o.Notify(It.IsAny<ILogMessage>())).Callback<ILogMessage>(m => messages.Add(m));
+
+			sut.Subscribe(observer.Object);
+			sut.Info(message);
+			sut.Unsubscribe(observer.Object);
+			sut.Warn(message);
+
+			observer.Verify(o => o.Notify(It.IsAny<ILogMessage>()), Times.Once());
+
+			Assert.IsTrue(messages.Count == 1);
+
+			Assert.IsTrue(messages[0].Severity == LogLevel.Info);
+			Assert.IsTrue(message.Equals(messages[0].Message));
+		}
+	}
+}

SafeExamBrowser.Core.UnitTests/SafeExamBrowser.Core.UnitTests.csproj

@@ -38,28 +38,39 @@
     <WarningLevel>4</WarningLevel>
   </PropertyGroup>
   <ItemGroup>
+    <Reference Include="Castle.Core, Version=4.1.0.0, Culture=neutral, PublicKeyToken=407dd0808d44fbdc, processorArchitecture=MSIL">
+      <HintPath>..\packages\Castle.Core.4.1.0\lib\net45\Castle.Core.dll</HintPath>
+    </Reference>
     <Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <HintPath>..\packages\MSTest.TestFramework.1.1.11\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.dll</HintPath>
     </Reference>
     <Reference Include="Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <HintPath>..\packages\MSTest.TestFramework.1.1.11\lib\net45\Microsoft.VisualStudio.TestPlatform.TestFramework.Extensions.dll</HintPath>
     </Reference>
+    <Reference Include="Moq, Version=4.7.63.0, Culture=neutral, PublicKeyToken=69f491c39445e920, processorArchitecture=MSIL">
+      <HintPath>..\packages\Moq.4.7.63\lib\net45\Moq.dll</HintPath>
+    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="I18n\TextTests.cs" />
+    <Compile Include="Logging\LoggerTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>
-    <None Include="packages.config" />
+    <ProjectReference Include="..\SafeExamBrowser.Contracts\SafeExamBrowser.Contracts.csproj">
-  </ItemGroup>
+      <Project>{47DA5933-BEF8-4729-94E6-ABDE2DB12262}</Project>
-  <ItemGroup>
+      <Name>SafeExamBrowser.Contracts</Name>
+    </ProjectReference>
     <ProjectReference Include="..\SafeExamBrowser.Core\SafeExamBrowser.Core.csproj">
       <Project>{3d6fdbb6-a4af-4626-bb2b-bf329d44f9cc}</Project>
       <Name>SafeExamBrowser.Core</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <None Include="packages.config" />
+  </ItemGroup>
   <Import Project="$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets" Condition="Exists('$(VSToolsPath)\TeamTest\Microsoft.TestTools.targets')" />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">

SafeExamBrowser.Core.UnitTests/packages.config

@@ -1,5 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
+  <package id="Castle.Core" version="4.1.0" targetFramework="net452" />
+  <package id="Moq" version="4.7.63" targetFramework="net452" />
   <package id="MSTest.TestAdapter" version="1.1.11" targetFramework="net452" />
   <package id="MSTest.TestFramework" version="1.1.11" targetFramework="net452" />
 </packages>

SafeExamBrowser.Core/Configuration/Settings.cs

@@ -0,0 +1,25 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+using System.IO;
+using SafeExamBrowser.Contracts.Configuration;
+
+namespace SafeExamBrowser.Core.Configuration
+{
+	public class Settings : ISettings
+	{
+		public string LogFolderPath
+		{
+			get
+			{
+				return Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "SafeExamBrowser", "Logs");
+			}
+		}
+	}
+}

SafeExamBrowser.Core/I18n/Text.cs

@@ -8,16 +8,13 @@
 
 using System;
 using System.Collections.Generic;
-using SafeExamBrowser.Core.Contracts;
+using SafeExamBrowser.Contracts.I18n;
 
 namespace SafeExamBrowser.Core.I18n
 {
-	public class Text
+	public class Text : IText
 	{
-		private static Text instance;
+		private readonly IDictionary<Key, string> cache;
-		private static readonly object @lock = new object();
-
-		private IDictionary<Key, string> cache = new Dictionary<Key, string>();
 
 		public Text(ITextResource resource)
 		{
@@ -26,25 +23,7 @@ namespace SafeExamBrowser.Core.I18n
 				throw new ArgumentNullException(nameof(resource));
 			}
 
-			cache = resource.LoadText();
+			cache = resource.LoadText() ?? new Dictionary<Key, string>();
-		}
-
-		public static Text Instance
-		{
-			get
-			{
-				lock (@lock)
-				{
-					return instance ?? new Text(new NullTextResource());
-				}
-			}
-			set
-			{
-				lock (@lock)
-				{
-					instance = value ?? throw new ArgumentNullException(nameof(value));
-				}
-			}
 		}
 
 		public string Get(Key key)

SafeExamBrowser.Core/I18n/Text.xml

@@ -1,6 +1,5 @@
 <?xml version="1.0" encoding="utf-8" ?>
 <Text>
-  <MessageBox_FatalErrorTitle>Fatal Error</MessageBox_FatalErrorTitle>
   <MessageBox_SingleInstance>You can only run one instance of SEB at a time.</MessageBox_SingleInstance>
   <MessageBox_SingleInstanceTitle>Startup Not Allowed</MessageBox_SingleInstanceTitle>
 </Text>

SafeExamBrowser.Core/I18n/XmlTextResource.cs

@@ -11,7 +11,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Reflection;
 using System.Xml.Linq;
-using SafeExamBrowser.Core.Contracts;
+using SafeExamBrowser.Contracts.I18n;
 
 namespace SafeExamBrowser.Core.I18n
 {

SafeExamBrowser.Core/Logging/LogFileWriter.cs

@@ -0,0 +1,50 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+using System.IO;
+using System.Text;
+using System.Threading;
+using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Core.Logging
+{
+	public class LogFileWriter : ILogObserver
+	{
+		private static readonly object @lock = new object();
+		private readonly string filePath;
+
+		public LogFileWriter(ISettings settings)
+		{
+			var fileName = $"{DateTime.Now.ToString("yyyy-MM-dd HH-mm-ss")}.txt";
+
+			if (!Directory.Exists(settings.LogFolderPath))
+			{
+				Directory.CreateDirectory(settings.LogFolderPath);
+			}
+
+			filePath = Path.Combine(settings.LogFolderPath, fileName);
+		}
+
+		public void Notify(ILogMessage message)
+		{
+			lock (@lock)
+			{
+				using (var stream = new StreamWriter(filePath, true, Encoding.UTF8))
+				{
+					var date = message.DateTime.ToString("yyyy-MM-dd HH:mm:ss");
+					var threadId = Thread.CurrentThread.ManagedThreadId;
+					var severity = message.Severity.ToString().ToUpper();
+
+					stream.WriteLine($"{date} [{threadId}] - {severity}: {message.Message}");
+				}
+			}
+		}
+	}
+}

SafeExamBrowser.Core/Logging/LogMessage.cs

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+using SafeExamBrowser.Contracts.Logging;
+
+namespace SafeExamBrowser.Core.Entities
+{
+	public class LogMessage : ILogMessage
+	{
+		public DateTime DateTime { get; private set; }
+		public LogLevel Severity { get; private set; }
+		public string Message { get; private set; }
+
+		public LogMessage(DateTime dateTime, LogLevel severity, string message)
+		{
+			DateTime = dateTime;
+			Severity = severity;
+			Message = message;
+		}
+
+		public object Clone()
+		{
+			return new LogMessage(DateTime, Severity, Message);
+		}
+	}
+}

SafeExamBrowser.Core/Logging/Logger.cs

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2017 ETH Zürich, Educational Development and Technology (LET)
+ * 
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using SafeExamBrowser.Contracts.Logging;
+using SafeExamBrowser.Core.Entities;
+
+namespace SafeExamBrowser.Core.Logging
+{
+	public class Logger : ILogger
+	{
+		private static readonly object @lock = new object();
+		private readonly IList<ILogMessage> log = new List<ILogMessage>();
+		private readonly IList<ILogObserver> observers = new List<ILogObserver>();
+
+		public void Error(string message)
+		{
+			Log(LogLevel.Error, message);
+		}
+
+		public void Info(string message)
+		{
+			Log(LogLevel.Info, message);
+		}
+
+		public void Warn(string message)
+		{
+			Log(LogLevel.Warn, message);
+		}
+
+		public IList<ILogMessage> GetLog()
+		{
+			lock (@lock)
+			{
+				return log.Select(m => m.Clone() as ILogMessage).ToList();
+			}
+		}
+
+		public void Subscribe(ILogObserver observer)
+		{
+			if (observer == null)
+			{
+				throw new ArgumentNullException(nameof(observer));
+			}
+
+			lock (@lock)
+			{
+				if (!observers.Contains(observer))
+				{
+					observers.Add(observer);
+				}
+			}
+		}
+
+		public void Unsubscribe(ILogObserver observer)
+		{
+			lock (@lock)
+			{
+				observers.Remove(observer);
+			}
+		}
+
+		private void Log(LogLevel severity, string message)
+		{
+			lock (@lock)
+			{
+				var entry = new LogMessage(DateTime.Now, severity, message);
+
+				log.Add(entry);
+				
+				foreach (var observer in observers)
+				{
+					observer.Notify(entry);
+				}
+			}
+		}
+	}
+}

SafeExamBrowser.Core/SafeExamBrowser.Core.csproj

@@ -40,18 +40,26 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
-    <Compile Include="Contracts\ITextResource.cs" />
+    <Compile Include="Configuration\Settings.cs" />
-    <Compile Include="Contracts\ITaskbar.cs" />
+    <Compile Include="Logging\LogFileWriter.cs" />
-    <Compile Include="I18n\Key.cs" />
+    <Compile Include="Logging\LogMessage.cs" />
-    <Compile Include="I18n\NullTextResource.cs" />
     <Compile Include="I18n\Text.cs" />
     <Compile Include="I18n\XmlTextResource.cs" />
+    <Compile Include="Logging\Logger.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
   <ItemGroup>
     <Content Include="I18n\Text.xml">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+      <SubType>Designer</SubType>
     </Content>
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\SafeExamBrowser.Contracts\SafeExamBrowser.Contracts.csproj">
+      <Project>{47DA5933-BEF8-4729-94E6-ABDE2DB12262}</Project>
+      <Name>SafeExamBrowser.Contracts</Name>
+    </ProjectReference>
+  </ItemGroup>
+  <ItemGroup />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
 </Project>

SafeExamBrowser.UserInterface/SafeExamBrowser.UserInterface.csproj

@@ -79,9 +79,9 @@
     </Page>
   </ItemGroup>
   <ItemGroup>
-    <ProjectReference Include="..\SafeExamBrowser.Core\SafeExamBrowser.Core.csproj">
+    <ProjectReference Include="..\SafeExamBrowser.Contracts\SafeExamBrowser.Contracts.csproj">
-      <Project>{3d6fdbb6-a4af-4626-bb2b-bf329d44f9cc}</Project>
+      <Project>{47DA5933-BEF8-4729-94E6-ABDE2DB12262}</Project>
-      <Name>SafeExamBrowser.Core</Name>
+      <Name>SafeExamBrowser.Contracts</Name>
     </ProjectReference>
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />

SafeExamBrowser.UserInterface/Taskbar.xaml.cs

@@ -7,7 +7,7 @@
  */
 
 using System.Windows;
-using SafeExamBrowser.Core.Contracts;
+using SafeExamBrowser.Contracts.UserInterface;
 
 namespace SafeExamBrowser.UserInterface
 {

SafeExamBrowser.sln

@@ -17,6 +17,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SafeExamBrowser.UserInterfa
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SafeExamBrowser.Core.UnitTests", "SafeExamBrowser.Core.UnitTests\SafeExamBrowser.Core.UnitTests.csproj", "{48B9F2A1-B87D-40F0-BEC9-399E8909860F}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SafeExamBrowser.Contracts", "SafeExamBrowser.Contracts\SafeExamBrowser.Contracts.csproj", "{47DA5933-BEF8-4729-94E6-ABDE2DB12262}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -39,6 +41,10 @@ Global
 		{48B9F2A1-B87D-40F0-BEC9-399E8909860F}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{48B9F2A1-B87D-40F0-BEC9-399E8909860F}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{48B9F2A1-B87D-40F0-BEC9-399E8909860F}.Release|Any CPU.Build.0 = Release|Any CPU
+		{47DA5933-BEF8-4729-94E6-ABDE2DB12262}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{47DA5933-BEF8-4729-94E6-ABDE2DB12262}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{47DA5933-BEF8-4729-94E6-ABDE2DB12262}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{47DA5933-BEF8-4729-94E6-ABDE2DB12262}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

SafeExamBrowser/App.cs

@@ -9,7 +9,7 @@
 using System;
 using System.Threading;
 using System.Windows;
-using SafeExamBrowser.Core.I18n;
+using SafeExamBrowser.Contracts.I18n;
 
 namespace SafeExamBrowser
 {
@@ -27,23 +27,28 @@ namespace SafeExamBrowser
 				compositionRoot.InitializeGlobalModules();
 				compositionRoot.BuildObjectGraph();
 
-				StartApplication(compositionRoot.Taskbar);
+				StartApplication(compositionRoot);
 			}
 			catch (Exception e)
 			{
-				MessageBox.Show(e.Message + "\n\n" + e.StackTrace, Text.Instance.Get(Key.MessageBox_FatalErrorTitle));
+				MessageBox.Show(e.Message + "\n\n" + e.StackTrace, "Fatal Error");
 			}
 		}
 
-		private static void StartApplication(Window taskbar)
+		private static void StartApplication(CompositionRoot compositionRoot)
 		{
+			compositionRoot.Logger.Info("Testing the log...");
+
 			if (NoInstanceRunning())
 			{
-				new App().Run(taskbar);
+				new App().Run(compositionRoot.Taskbar);
 			}
 			else
 			{
-				MessageBox.Show(Text.Instance.Get(Key.MessageBox_SingleInstance), Text.Instance.Get(Key.MessageBox_SingleInstanceTitle));
+				var message = compositionRoot.Text.Get(Key.MessageBox_SingleInstance);
+				var title = compositionRoot.Text.Get(Key.MessageBox_SingleInstanceTitle);
+
+				MessageBox.Show(message, title);
 			}
 		}
 

SafeExamBrowser/CompositionRoot.cs

@@ -7,18 +7,29 @@
  */
 
 using System.Windows;
+using SafeExamBrowser.Contracts.Configuration;
+using SafeExamBrowser.Contracts.I18n;
+using SafeExamBrowser.Contracts.Logging;
+using SafeExamBrowser.Core.Configuration;
 using SafeExamBrowser.Core.I18n;
+using SafeExamBrowser.Core.Logging;
 using SafeExamBrowser.UserInterface;
 
 namespace SafeExamBrowser
 {
 	class CompositionRoot
 	{
+		public ILogger Logger { get; private set; }
+		public ISettings Settings { get; private set; }
+		public IText Text { get; private set; }
 		public Window Taskbar { get; private set; }
 
 		public void InitializeGlobalModules()
 		{
-			Text.Instance = new Text(new XmlTextResource());
+			Settings = new Settings();
+			Logger = new Logger();
+			Logger.Subscribe(new LogFileWriter(Settings));
+			Text = new Text(new XmlTextResource());
 		}
 
 		public void BuildObjectGraph()

SafeExamBrowser/SafeExamBrowser.csproj

@@ -13,6 +13,21 @@
     <ProjectTypeGuids>{60dc8134-eba5-43b8-bcc9-bb4bc16c2548};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}</ProjectTypeGuids>
     <WarningLevel>4</WarningLevel>
     <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <PublishUrl>publish\</PublishUrl>
+    <Install>true</Install>
+    <InstallFrom>Disk</InstallFrom>
+    <UpdateEnabled>false</UpdateEnabled>
+    <UpdateMode>Foreground</UpdateMode>
+    <UpdateInterval>7</UpdateInterval>
+    <UpdateIntervalUnits>Days</UpdateIntervalUnits>
+    <UpdatePeriodically>false</UpdatePeriodically>
+    <UpdateRequired>false</UpdateRequired>
+    <MapFileExtensions>true</MapFileExtensions>
+    <ApplicationRevision>0</ApplicationRevision>
+    <ApplicationVersion>3.0.0.%2a</ApplicationVersion>
+    <IsWebBootstrapper>false</IsWebBootstrapper>
+    <UseApplicationTrust>false</UseApplicationTrust>
+    <BootstrapperEnabled>true</BootstrapperEnabled>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -78,6 +93,10 @@
     <None Include="App.config" />
   </ItemGroup>
   <ItemGroup>
+    <ProjectReference Include="..\SafeExamBrowser.Contracts\SafeExamBrowser.Contracts.csproj">
+      <Project>{47DA5933-BEF8-4729-94E6-ABDE2DB12262}</Project>
+      <Name>SafeExamBrowser.Contracts</Name>
+    </ProjectReference>
     <ProjectReference Include="..\SafeExamBrowser.Core\SafeExamBrowser.Core.csproj">
       <Project>{3d6fdbb6-a4af-4626-bb2b-bf329d44f9cc}</Project>
       <Name>SafeExamBrowser.Core</Name>
@@ -87,5 +106,17 @@
       <Name>SafeExamBrowser.UserInterface</Name>
     </ProjectReference>
   </ItemGroup>
+  <ItemGroup>
+    <BootstrapperPackage Include=".NETFramework,Version=v4.5.2">
+      <Visible>False</Visible>
+      <ProductName>Microsoft .NET Framework 4.5.2 %28x86 and x64%29</ProductName>
+      <Install>true</Install>
+    </BootstrapperPackage>
+    <BootstrapperPackage Include="Microsoft.Net.Framework.3.5.SP1">
+      <Visible>False</Visible>
+      <ProductName>.NET Framework 3.5 SP1</ProductName>
+      <Install>false</Install>
+    </BootstrapperPackage>
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
 </Project>