diff --git a/CHANGES b/CHANGES
index 09d0aac22..270aa3191 100644
--- a/CHANGES
+++ b/CHANGES
@@ -34,9 +34,15 @@ This release contains contributions from (alphabetically by first name):
 
 ## Modules ##
  - *packages* now reports more details in the installation progress-bar.
- - *netinstall* module supports and `expanded` key, which will pre-expand
+ - *netinstall* module supports an `expanded` key, which will pre-expand
    a group (as if the user had pressed the arrow-button in the tree-view).
-   This only affects the UI.
+   This only affects the UI, and only the **outermost** level of groups.
+ - *netinstall* module now supports a special value for *groupsUrl*.
+   Setting this to *local* will read the groups directly from the
+   configuration file.
+ - *netinstall* groups now support a new key `immutable` which prevents
+   their check-state from being changed (they are shown, or hidden,
+   as usual and can be expanded).
  - Modules that use QML need a new import line. The QML file for the
    module is configured through new keys *qmlSearch* and *qmlFilename*
    (previously those were without the `qml` prefix, which invites name
diff --git a/CMakeModules/CalamaresAddTest.cmake b/CMakeModules/CalamaresAddTest.cmake
index 36be0f03e..65f9389e8 100644
--- a/CMakeModules/CalamaresAddTest.cmake
+++ b/CMakeModules/CalamaresAddTest.cmake
@@ -50,7 +50,7 @@ function( calamares_add_test )
                 Qt5::Test
             )
         calamares_automoc( ${TEST_NAME} )
-        target_compile_definitions( ${TEST_NAME} PRIVATE -DBUILD_AS_TEST ${TEST_DEFINITIONS} )
+        target_compile_definitions( ${TEST_NAME} PRIVATE -DBUILD_AS_TEST="${CMAKE_CURRENT_SOURCE_DIR}"  ${TEST_DEFINITIONS} )
         if( TEST_GUI )
             target_link_libraries( ${TEST_NAME} calamaresui Qt5::Gui )
         endif()
diff --git a/src/modules/netinstall/CMakeLists.txt b/src/modules/netinstall/CMakeLists.txt
index c5eddd32b..3e6ac3cb5 100644
--- a/src/modules/netinstall/CMakeLists.txt
+++ b/src/modules/netinstall/CMakeLists.txt
@@ -2,6 +2,7 @@ calamares_add_plugin( netinstall
     TYPE viewmodule
     EXPORT_MACRO PLUGINDLLEXPORT_PRO
     SOURCES
+        Config.cpp
         NetInstallViewStep.cpp
         NetInstallPage.cpp
         PackageTreeItem.cpp
@@ -16,3 +17,14 @@ calamares_add_plugin( netinstall
         yamlcpp
     SHARED_LIB
 )
+
+calamares_add_test(
+    netinstalltest
+    SOURCES
+        Tests.cpp
+        PackageTreeItem.cpp
+        PackageModel.cpp
+    LIBRARIES
+        Qt5::Gui
+)
+
diff --git a/src/modules/netinstall/Config.cpp b/src/modules/netinstall/Config.cpp
new file mode 100644
index 000000000..78718add1
--- /dev/null
+++ b/src/modules/netinstall/Config.cpp
@@ -0,0 +1,156 @@
+/*
+ *   Copyright 2016, Luca Giambonini <almack@chakraos.org>
+ *   Copyright 2016, Lisa Vitolo     <shainer@chakraos.org>
+ *   Copyright 2017, Kyle Robbertze  <krobbertze@gmail.com>
+ *   Copyright 2017-2018, 2020, Adriaan de Groot <groot@kde.org>
+ *   Copyright 2017, Gabriel Craciunescu <crazy@frugalware.org>
+ *
+ *   Calamares is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "Config.h"
+
+#include "network/Manager.h"
+#include "utils/Logger.h"
+#include "utils/Yaml.h"
+
+#include <QNetworkReply>
+
+Config::Config( QObject* parent )
+    : QObject( parent )
+    , m_model( new PackageModel( this ) )
+{
+}
+
+Config::~Config() {}
+
+QString
+Config::status() const
+{
+    switch ( m_status )
+    {
+    case Status::Ok:
+        return QString();
+    case Status::FailedBadConfiguration:
+        return tr( "Network Installation. (Disabled: Incorrect configuration)" );
+    case Status::FailedBadData:
+        return tr( "Network Installation. (Disabled: Received invalid groups data)" );
+    case Status::FailedInternalError:
+        return tr( "Network Installation. (Disabled: internal error)" );
+    case Status::FailedNetworkError:
+        return tr( "Network Installation. (Disabled: Unable to fetch package lists, check your network connection)" );
+    }
+    NOTREACHED return QString();
+}
+
+
+void
+Config::setStatus( Status s )
+{
+    m_status = s;
+    emit statusChanged( status() );
+}
+
+void
+Config::loadGroupList( const QVariantList& groupData )
+{
+    m_model->setupModelData( groupData );
+    emit statusReady();
+}
+
+void
+Config::loadGroupList( const QUrl& url )
+{
+    if ( !url.isValid() )
+    {
+        setStatus( Status::FailedBadConfiguration );
+    }
+
+    using namespace CalamaresUtils::Network;
+
+    cDebug() << "NetInstall loading groups from" << url;
+    QNetworkReply* reply = Manager::instance().asynchronousGet(
+        url,
+        RequestOptions( RequestOptions::FakeUserAgent | RequestOptions::FollowRedirect, std::chrono::seconds( 30 ) ) );
+
+    if ( !reply )
+    {
+        cDebug() << Logger::Continuation << "request failed immediately.";
+        setStatus( Status::FailedBadConfiguration );
+    }
+    else
+    {
+        m_reply = reply;
+        connect( reply, &QNetworkReply::finished, this, &Config::receivedGroupData );
+    }
+}
+
+/// @brief Convenience to zero out and deleteLater on the reply, used in dataIsHere
+struct ReplyDeleter
+{
+    QNetworkReply*& p;
+
+    ~ReplyDeleter()
+    {
+        if ( p )
+        {
+            p->deleteLater();
+        }
+        p = nullptr;
+    }
+};
+
+void
+Config::receivedGroupData()
+{
+    if ( !m_reply || !m_reply->isFinished() )
+    {
+        cWarning() << "NetInstall data called too early.";
+        setStatus( Status::FailedInternalError );
+        return;
+    }
+
+    cDebug() << "NetInstall group data received" << m_reply->size() << "bytes from" << m_reply->url();
+
+    ReplyDeleter d { m_reply };
+
+    // If m_required is *false* then we still say we're ready
+    // even if the reply is corrupt or missing.
+    if ( m_reply->error() != QNetworkReply::NoError )
+    {
+        cWarning() << "unable to fetch netinstall package lists.";
+        cDebug() << Logger::SubEntry << "Netinstall reply error: " << m_reply->error();
+        cDebug() << Logger::SubEntry << "Request for url: " << m_reply->url().toString()
+                 << " failed with: " << m_reply->errorString();
+        setStatus( Status::FailedNetworkError );
+        return;
+    }
+
+    QByteArray yamlData = m_reply->readAll();
+    try
+    {
+        YAML::Node groups = YAML::Load( yamlData.constData() );
+
+        if ( !groups.IsSequence() )
+        {
+            cWarning() << "NetInstall groups data does not form a sequence.";
+        }
+        loadGroupList( CalamaresUtils::yamlSequenceToVariant( groups ) );
+    }
+    catch ( YAML::Exception& e )
+    {
+        CalamaresUtils::explainYamlException( e, yamlData, "netinstall groups data" );
+        setStatus( Status::FailedBadData );
+    }
+}
diff --git a/src/modules/netinstall/Config.h b/src/modules/netinstall/Config.h
new file mode 100644
index 000000000..781c9be5d
--- /dev/null
+++ b/src/modules/netinstall/Config.h
@@ -0,0 +1,87 @@
+/*
+ *   Copyright 2016, Luca Giambonini <almack@chakraos.org>
+ *   Copyright 2016, Lisa Vitolo     <shainer@chakraos.org>
+ *   Copyright 2017, Kyle Robbertze  <krobbertze@gmail.com>
+ *   Copyright 2017-2018, 2020, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef NETINSTALL_CONFIG_H
+#define NETINSTALL_CONFIG_H
+
+#include "PackageModel.h"
+
+#include <QObject>
+#include <QUrl>
+
+class QNetworkReply;
+
+class Config : public QObject
+{
+    Q_OBJECT
+
+    Q_PROPERTY( PackageModel* packageModel MEMBER m_model FINAL )
+    Q_PROPERTY( QString status READ status NOTIFY statusChanged FINAL )
+
+public:
+    Config( QObject* parent = nullptr );
+    virtual ~Config();
+
+    enum class Status
+    {
+        Ok,
+        FailedBadConfiguration,
+        FailedInternalError,
+        FailedNetworkError,
+        FailedBadData
+    };
+
+    QString status() const;
+    void setStatus( Status s );
+
+    bool required() const { return m_required; }
+    void setRequired( bool r ) { m_required = r; }
+
+    /** @brief Retrieves the groups, with name, description and packages
+     *
+     * Loads data from the given URL. Once done, the data is parsed
+     * and passed on to the other loadGroupList() method.
+     */
+    void loadGroupList( const QUrl& url );
+
+    /** @brief Fill model from parsed data.
+     *
+     * Fills the model with a list of groups -- which can contain
+     * subgroups and packages -- from @p groupData.
+     */
+    void loadGroupList( const QVariantList& groupData );
+
+    PackageModel* model() const { return m_model; }
+
+signals:
+    void statusChanged( QString status );  ///< Something changed
+    void statusReady();  ///< Loading groups is complete
+
+private slots:
+    void receivedGroupData();  ///< From async-loading group data
+
+private:
+    PackageModel* m_model = nullptr;
+    QNetworkReply* m_reply = nullptr;  // For fetching data
+    Status m_status = Status::Ok;
+    bool m_required = false;
+};
+
+#endif
diff --git a/src/modules/netinstall/NetInstallPage.cpp b/src/modules/netinstall/NetInstallPage.cpp
index e21814caa..688e99b09 100644
--- a/src/modules/netinstall/NetInstallPage.cpp
+++ b/src/modules/netinstall/NetInstallPage.cpp
@@ -34,22 +34,21 @@
 #include <QHeaderView>
 #include <QNetworkReply>
 
-NetInstallPage::NetInstallPage( QWidget* parent )
+NetInstallPage::NetInstallPage( Config* c, QWidget* parent )
     : QWidget( parent )
+    , m_config( c )
     , ui( new Ui::Page_NetInst )
-    , m_reply( nullptr )
-    , m_groups( nullptr )
 {
     ui->setupUi( this );
+    ui->groupswidget->setModel( c->model() );
+    connect( c, &Config::statusChanged, this, &NetInstallPage::setStatus );
+    connect( c, &Config::statusReady, this, &NetInstallPage::expandGroups );
+
     setPageTitle( nullptr );
     CALAMARES_RETRANSLATE_SLOT( &NetInstallPage::retranslate );
 }
 
-NetInstallPage::~NetInstallPage()
-{
-    delete m_groups;
-    delete m_reply;
-}
+NetInstallPage::~NetInstallPage() {}
 
 void
 NetInstallPage::setPageTitle( CalamaresUtils::Locale::TranslatedString* t )
@@ -69,147 +68,34 @@ NetInstallPage::setPageTitle( CalamaresUtils::Locale::TranslatedString* t )
 void
 NetInstallPage::retranslate()
 {
-    if ( ui && m_title )
+    if ( m_title )
     {
         ui->label->setText( m_title->get() );  // That's get() on the TranslatedString
     }
+    ui->netinst_status->setText( m_config->status() );
 }
 
-bool
-NetInstallPage::readGroups( const QByteArray& yamlData )
-{
-    try
-    {
-        YAML::Node groups = YAML::Load( yamlData.constData() );
-
-        if ( !groups.IsSequence() )
-        {
-            cWarning() << "netinstall groups data does not form a sequence.";
-        }
-        Q_ASSERT( groups.IsSequence() );
-        m_groups = new PackageModel( groups );
-        return true;
-    }
-    catch ( YAML::Exception& e )
-    {
-        CalamaresUtils::explainYamlException( e, yamlData, "netinstall groups data" );
-        return false;
-    }
-}
-
-/// @brief Convenience to zero out and deleteLater on the reply, used in dataIsHere
-struct ReplyDeleter
-{
-    QNetworkReply*& p;
-
-    ~ReplyDeleter()
-    {
-        if ( p )
-        {
-            p->deleteLater();
-        }
-        p = nullptr;
-    }
-};
-
 void
-NetInstallPage::dataIsHere()
+NetInstallPage::expandGroups()
 {
-    if ( !m_reply || !m_reply->isFinished() )
-    {
-        cWarning() << "NetInstall data called too early.";
-        return;
-    }
-
-    cDebug() << "NetInstall group data received" << m_reply->url();
-
-    ReplyDeleter d { m_reply };
-
-    // If m_required is *false* then we still say we're ready
-    // even if the reply is corrupt or missing.
-    if ( m_reply->error() != QNetworkReply::NoError )
-    {
-        cWarning() << "unable to fetch netinstall package lists.";
-        cDebug() << Logger::SubEntry << "Netinstall reply error: " << m_reply->error();
-        cDebug() << Logger::SubEntry << "Request for url: " << m_reply->url().toString()
-                 << " failed with: " << m_reply->errorString();
-        ui->netinst_status->setText(
-            tr( "Network Installation. (Disabled: Unable to fetch package lists, check your network connection)" ) );
-        emit checkReady( !m_required );
-        return;
-    }
-
-    if ( !readGroups( m_reply->readAll() ) )
-    {
-        cWarning() << "netinstall groups data was received, but invalid.";
-        cDebug() << Logger::SubEntry << "Url:     " << m_reply->url().toString();
-        cDebug() << Logger::SubEntry << "Headers: " << m_reply->rawHeaderList();
-        ui->netinst_status->setText( tr( "Network Installation. (Disabled: Received invalid groups data)" ) );
-        emit checkReady( !m_required );
-        return;
-    }
-
-    retranslate();  // For changed model
-    ui->groupswidget->setModel( m_groups );
-    ui->groupswidget->header()->setSectionResizeMode( 0, QHeaderView::ResizeToContents );
-    ui->groupswidget->header()->setSectionResizeMode( 1, QHeaderView::Stretch );
-
+    auto* model = m_config->model();
     // Go backwards because expanding a group may cause rows to appear below it
-    for ( int i = m_groups->rowCount() - 1; i >= 0; --i )
+    for ( int i = model->rowCount() - 1; i >= 0; --i )
     {
-        auto index = m_groups->index(i,0);
-        if ( m_groups->data(index, PackageModel::MetaExpandRole).toBool() )
+        auto index = model->index( i, 0 );
+        if ( model->data( index, PackageModel::MetaExpandRole ).toBool() )
         {
-            ui->groupswidget->setExpanded(index, true);
+            ui->groupswidget->setExpanded( index, true );
         }
     }
-
-    emit checkReady( true );
-}
-
-PackageModel::PackageItemDataList
-NetInstallPage::selectedPackages() const
-{
-    if ( m_groups )
-    {
-        return m_groups->getPackages();
-    }
-    else
-    {
-        cWarning() << "no netinstall groups are available.";
-        return PackageModel::PackageItemDataList();
-    }
 }
 
 void
-NetInstallPage::loadGroupList( const QString& confUrl )
+NetInstallPage::setStatus( QString s )
 {
-    using namespace CalamaresUtils::Network;
-
-    cDebug() << "NetInstall loading groups from" << confUrl;
-    QNetworkReply* reply = Manager::instance().asynchronousGet(
-        QUrl( confUrl ),
-        RequestOptions( RequestOptions::FakeUserAgent | RequestOptions::FollowRedirect, std::chrono::seconds( 30 ) ) );
-
-    if ( !reply )
-    {
-        cDebug() << Logger::Continuation << "request failed immediately.";
-        ui->netinst_status->setText( tr( "Network Installation. (Disabled: Incorrect configuration)" ) );
-    }
-    else
-    {
-        m_reply = reply;
-        connect( reply, &QNetworkReply::finished, this, &NetInstallPage::dataIsHere );
-    }
+    ui->netinst_status->setText( s );
 }
 
-void
-NetInstallPage::setRequired( bool b )
-{
-    m_required = b;
-}
-
-
 void
 NetInstallPage::onActivate()
 {
diff --git a/src/modules/netinstall/NetInstallPage.h b/src/modules/netinstall/NetInstallPage.h
index 12633c6b9..13a106eaf 100644
--- a/src/modules/netinstall/NetInstallPage.h
+++ b/src/modules/netinstall/NetInstallPage.h
@@ -21,6 +21,7 @@
 #ifndef NETINSTALLPAGE_H
 #define NETINSTALLPAGE_H
 
+#include "Config.h"
 #include "PackageModel.h"
 #include "PackageTreeItem.h"
 
@@ -42,7 +43,7 @@ class NetInstallPage : public QWidget
 {
     Q_OBJECT
 public:
-    NetInstallPage( QWidget* parent = nullptr );
+    NetInstallPage( Config* config, QWidget* parent = nullptr );
     virtual ~NetInstallPage();
 
     /** @brief Sets the page title
@@ -58,45 +59,22 @@ public:
 
     void onActivate();
 
-    /** @brief Retrieves the groups, with name, description and packages
-     *
-     * Loads data from the given URL. This should be called before
-     * displaying the page.
-     */
-    void loadGroupList( const QString& url );
-
-    // Sets the "required" state of netinstall data. Influences whether
-    // corrupt or unavailable data causes checkReady() to be emitted
-    // true (not-required) or false.
-    void setRequired( bool );
-    bool getRequired() const { return m_required; }
-
-    // Returns the list of packages belonging to groups that are
-    // selected in the view in this given moment. No data is cached here, so
-    // this function does not have constant time.
-    PackageModel::PackageItemDataList selectedPackages() const;
-
 public slots:
-    void dataIsHere();
-
     void retranslate();
+    void setStatus( QString s );
 
-signals:
-    void checkReady( bool );
+    /** @brief Expand entries that should be pre-expanded.
+     *
+     * Follows the *expanded* key / the startExpanded field in the
+     * group entries of the model. Call this after filling up the model.
+     */
+    void expandGroups();
 
 private:
-    // Takes the YAML data representing the groups and reads them into the
-    // m_groups and m_groupOrder internal structures. See the README.md
-    // of this module to know the format expected of the YAML files.
-    bool readGroups( const QByteArray& yamlData );
-
+    Config* m_config;
     Ui::Page_NetInst* ui;
 
     std::unique_ptr< CalamaresUtils::Locale::TranslatedString > m_title;  // Above the treeview
-
-    QNetworkReply* m_reply;
-    PackageModel* m_groups;
-    bool m_required;
 };
 
 #endif  // NETINSTALLPAGE_H
diff --git a/src/modules/netinstall/NetInstallViewStep.cpp b/src/modules/netinstall/NetInstallViewStep.cpp
index cb79982f9..3eba788db 100644
--- a/src/modules/netinstall/NetInstallViewStep.cpp
+++ b/src/modules/netinstall/NetInstallViewStep.cpp
@@ -32,12 +32,11 @@ CALAMARES_PLUGIN_FACTORY_DEFINITION( NetInstallViewStepFactory, registerPlugin<
 
 NetInstallViewStep::NetInstallViewStep( QObject* parent )
     : Calamares::ViewStep( parent )
-    , m_widget( new NetInstallPage() )
-    , m_nextEnabled( false )
+    , m_widget( new NetInstallPage( &m_config ) )
     , m_sidebarLabel( nullptr )
+    , m_nextEnabled( false )
 {
-    emit nextStatusChanged( true );
-    connect( m_widget, &NetInstallPage::checkReady, this, &NetInstallViewStep::nextIsReady );
+    connect( &m_config, &Config::statusReady, this, &NetInstallViewStep::nextIsReady );
 }
 
 
@@ -56,7 +55,7 @@ NetInstallViewStep::prettyName() const
 {
     return m_sidebarLabel ? m_sidebarLabel->get() : tr( "Package selection" );
 
-#if defined(TABLE_OF_TRANSLATIONS)
+#if defined( TABLE_OF_TRANSLATIONS )
     NOTREACHED
     // This is a table of "standard" labels for this module. If you use them
     // in the label: sidebar: section of the config file, the existing
@@ -86,7 +85,7 @@ NetInstallViewStep::widget()
 bool
 NetInstallViewStep::isNextEnabled() const
 {
-    return m_nextEnabled;
+    return !m_config.required() || m_nextEnabled;
 }
 
 
@@ -111,10 +110,10 @@ NetInstallViewStep::isAtEnd() const
 }
 
 
-QList< Calamares::job_ptr >
+Calamares::JobList
 NetInstallViewStep::jobs() const
 {
-    return m_jobs;
+    return Calamares::JobList();
 }
 
 
@@ -127,7 +126,7 @@ NetInstallViewStep::onActivate()
 void
 NetInstallViewStep::onLeave()
 {
-    PackageModel::PackageItemDataList packages = m_widget->selectedPackages();
+    auto packages = m_config.model()->getPackages();
     cDebug() << "Netinstall: Processing" << packages.length() << "packages.";
 
     static const char PACKAGEOP[] = "packageOperations";
@@ -158,13 +157,13 @@ NetInstallViewStep::onLeave()
 
     for ( const auto& package : packages )
     {
-        if ( package.isCritical )
+        if ( package->isCritical() )
         {
-            installPackages.append( package.toOperation() );
+            installPackages.append( package->toOperation() );
         }
         else
         {
-            tryInstallPackages.append( package.toOperation() );
+            tryInstallPackages.append( package->toOperation() );
         }
     }
 
@@ -192,16 +191,16 @@ NetInstallViewStep::onLeave()
 }
 
 void
-NetInstallViewStep::nextIsReady( bool b )
+NetInstallViewStep::nextIsReady()
 {
-    m_nextEnabled = b;
-    emit nextStatusChanged( b );
+    m_nextEnabled = true;
+    emit nextStatusChanged( true );
 }
 
 void
 NetInstallViewStep::setConfigurationMap( const QVariantMap& configurationMap )
 {
-    m_widget->setRequired( CalamaresUtils::getBool( configurationMap, "required", false ) );
+    m_config.setRequired( CalamaresUtils::getBool( configurationMap, "required", false ) );
 
     QString groupsUrl = CalamaresUtils::getString( configurationMap, "groupsUrl" );
     if ( !groupsUrl.isEmpty() )
@@ -209,7 +208,15 @@ NetInstallViewStep::setConfigurationMap( const QVariantMap& configurationMap )
         // Keep putting groupsUrl into the global storage,
         // even though it's no longer used for in-module data-passing.
         Calamares::JobQueue::instance()->globalStorage()->insert( "groupsUrl", groupsUrl );
-        m_widget->loadGroupList( groupsUrl );
+        if ( groupsUrl == QStringLiteral( "local" ) )
+        {
+            QVariantList l = configurationMap.value( "groups" ).toList();
+            m_config.loadGroupList( l );
+        }
+        else
+        {
+            m_config.loadGroupList( groupsUrl );
+        }
     }
 
     bool bogus = false;
diff --git a/src/modules/netinstall/NetInstallViewStep.h b/src/modules/netinstall/NetInstallViewStep.h
index ad796b8b2..d2114a346 100644
--- a/src/modules/netinstall/NetInstallViewStep.h
+++ b/src/modules/netinstall/NetInstallViewStep.h
@@ -20,6 +20,8 @@
 #ifndef NETINSTALLVIEWSTEP_H
 #define NETINSTALLVIEWSTEP_H
 
+#include "Config.h"
+
 #include "DllMacro.h"
 #include "locale/TranslatableConfiguration.h"
 #include "utils/PluginFactory.h"
@@ -47,7 +49,7 @@ public:
     bool isAtBeginning() const override;
     bool isAtEnd() const override;
 
-    QList< Calamares::job_ptr > jobs() const override;
+    Calamares::JobList jobs() const override;
 
     void onActivate() override;
 
@@ -57,13 +59,14 @@ public:
     void setConfigurationMap( const QVariantMap& configurationMap ) override;
 
 public slots:
-    void nextIsReady( bool );
+    void nextIsReady();
 
 private:
+    Config m_config;
+
     NetInstallPage* m_widget;
-    bool m_nextEnabled;
     CalamaresUtils::Locale::TranslatedString* m_sidebarLabel;  // As it appears in the sidebar
-    QList< Calamares::job_ptr > m_jobs;
+    bool m_nextEnabled = false;
 };
 
 CALAMARES_PLUGIN_FACTORY_DECLARATION( NetInstallViewStepFactory )
diff --git a/src/modules/netinstall/PackageModel.cpp b/src/modules/netinstall/PackageModel.cpp
index 215ac2912..dad2207b2 100644
--- a/src/modules/netinstall/PackageModel.cpp
+++ b/src/modules/netinstall/PackageModel.cpp
@@ -1,7 +1,7 @@
 /* === This file is part of Calamares - <https://github.com/calamares> ===
  *
  *   Copyright (c) 2017, Kyle Robbertze <kyle@aims.ac.za>
- *   Copyright 2017-2018, Adriaan de Groot <groot@kde.org>
+ *   Copyright 2017-2018, 2020, Adriaan de Groot <groot@kde.org>
  *
  *   Calamares is free software: you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -19,13 +19,12 @@
 
 #include "PackageModel.h"
 
+#include "utils/Variant.h"
 #include "utils/Yaml.h"
 
-PackageModel::PackageModel( const YAML::Node& data, QObject* parent )
+PackageModel::PackageModel( QObject* parent )
     : QAbstractItemModel( parent )
 {
-    m_rootItem = new PackageTreeItem();
-    setupModelData( data, m_rootItem );
 }
 
 PackageModel::~PackageModel()
@@ -36,7 +35,7 @@ PackageModel::~PackageModel()
 QModelIndex
 PackageModel::index( int row, int column, const QModelIndex& parent ) const
 {
-    if ( !hasIndex( row, column, parent ) )
+    if ( !m_rootItem || !hasIndex( row, column, parent ) )
     {
         return QModelIndex();
     }
@@ -66,7 +65,7 @@ PackageModel::index( int row, int column, const QModelIndex& parent ) const
 QModelIndex
 PackageModel::parent( const QModelIndex& index ) const
 {
-    if ( !index.isValid() )
+    if ( !m_rootItem || !index.isValid() )
     {
         return QModelIndex();
     }
@@ -84,7 +83,7 @@ PackageModel::parent( const QModelIndex& index ) const
 int
 PackageModel::rowCount( const QModelIndex& parent ) const
 {
-    if ( parent.column() > 0 )
+    if ( !m_rootItem || ( parent.column() > 0 ) )
     {
         return 0;
     }
@@ -111,7 +110,7 @@ PackageModel::columnCount( const QModelIndex& ) const
 QVariant
 PackageModel::data( const QModelIndex& index, int role ) const
 {
-    if ( !index.isValid() )
+    if ( !m_rootItem || !index.isValid() )
     {
         return QVariant();
     }
@@ -120,7 +119,7 @@ PackageModel::data( const QModelIndex& index, int role ) const
     switch ( role )
     {
     case Qt::CheckStateRole:
-        return index.column() == NameColumn ? item->isSelected() : QVariant();
+        return index.column() == NameColumn ? ( item->isImmutable() ? QVariant() : item->isSelected() ) : QVariant();
     case Qt::DisplayRole:
         return item->isHidden() ? QVariant() : item->data( index.column() );
     case MetaExpandRole:
@@ -133,6 +132,11 @@ PackageModel::data( const QModelIndex& index, int role ) const
 bool
 PackageModel::setData( const QModelIndex& index, const QVariant& value, int role )
 {
+    if ( !m_rootItem )
+    {
+        return false;
+    }
+
     if ( role == Qt::CheckStateRole && index.isValid() )
     {
         PackageTreeItem* item = static_cast< PackageTreeItem* >( index.internalPointer() );
@@ -148,12 +152,17 @@ PackageModel::setData( const QModelIndex& index, const QVariant& value, int role
 Qt::ItemFlags
 PackageModel::flags( const QModelIndex& index ) const
 {
-    if ( !index.isValid() )
+    if ( !m_rootItem || !index.isValid() )
     {
         return Qt::ItemFlags();
     }
     if ( index.column() == NameColumn )
     {
+        PackageTreeItem* item = static_cast< PackageTreeItem* >( index.internalPointer() );
+        if ( item->isImmutable() )
+        {
+            return QAbstractItemModel::flags( index );  //Qt::NoItemFlags;
+        }
         return Qt::ItemIsUserCheckable | QAbstractItemModel::flags( index );
     }
     return QAbstractItemModel::flags( index );
@@ -169,109 +178,84 @@ PackageModel::headerData( int section, Qt::Orientation orientation, int role ) c
     return QVariant();
 }
 
-QList< PackageTreeItem::ItemData >
+PackageTreeItem::List
 PackageModel::getPackages() const
 {
-    QList< PackageTreeItem* > items = getItemPackages( m_rootItem );
+    if ( !m_rootItem )
+    {
+        return PackageTreeItem::List();
+    }
+
+    auto items = getItemPackages( m_rootItem );
     for ( auto package : m_hiddenItems )
+    {
         if ( package->hiddenSelected() )
         {
             items.append( getItemPackages( package ) );
         }
-    QList< PackageTreeItem::ItemData > packages;
-    for ( auto item : items )
-    {
-        PackageTreeItem::ItemData itemData;
-        itemData.preScript = item->parentItem()->preScript();  // Only groups have hooks
-        itemData.packageName = item->packageName();  // this seg faults
-        itemData.postScript = item->parentItem()->postScript();  // Only groups have hooks
-        itemData.isCritical = item->parentItem()->isCritical();  // Only groups are critical
-        packages.append( itemData );
     }
-    return packages;
+    return items;
 }
 
-QList< PackageTreeItem* >
+PackageTreeItem::List
 PackageModel::getItemPackages( PackageTreeItem* item ) const
 {
-    QList< PackageTreeItem* > selectedPackages;
+    PackageTreeItem::List selectedPackages;
     for ( int i = 0; i < item->childCount(); i++ )
     {
-        if ( item->child( i )->isSelected() == Qt::Unchecked )
+        auto* child = item->child( i );
+        if ( child->isSelected() == Qt::Unchecked )
         {
             continue;
         }
 
-        if ( !item->child( i )->childCount() )  // package
+        if ( child->isPackage() )  // package
         {
-            selectedPackages.append( item->child( i ) );
+            selectedPackages.append( child );
         }
         else
         {
-            selectedPackages.append( getItemPackages( item->child( i ) ) );
+            selectedPackages.append( getItemPackages( child ) );
         }
     }
     return selectedPackages;
 }
 
-static QString
-getString( const YAML::Node& itemDefinition, const char* key )
-{
-    return itemDefinition[ key ] ? CalamaresUtils::yamlToVariant( itemDefinition[ key ] ).toString() : QString();
-}
-
-static bool
-getBool( const YAML::Node& itemDefinition, const char* key )
-{
-    return itemDefinition[ key ] ? CalamaresUtils::yamlToVariant( itemDefinition[ key ] ).toBool() : false;
-}
-
 void
-PackageModel::setupModelData( const YAML::Node& data, PackageTreeItem* parent )
+PackageModel::setupModelData( const QVariantList& groupList, PackageTreeItem* parent )
 {
-    for ( YAML::const_iterator it = data.begin(); it != data.end(); ++it )
+    for ( const auto& group : groupList )
     {
-        const YAML::Node itemDefinition = *it;
-
-        QString name( tr( CalamaresUtils::yamlToVariant( itemDefinition[ "name" ] ).toByteArray() ) );
-        QString description( tr( CalamaresUtils::yamlToVariant( itemDefinition[ "description" ] ).toByteArray() ) );
-
-        PackageTreeItem::ItemData itemData;
-        itemData.name = name;
-        itemData.description = description;
-
-        itemData.preScript = getString( itemDefinition, "pre-install" );
-        itemData.postScript = getString( itemDefinition, "post-install" );
-        itemData.isCritical = getBool( itemDefinition, "critical" );
-        itemData.isHidden = getBool( itemDefinition, "hidden" );
-        itemData.startExpanded = getBool( itemDefinition, "expanded" );
-
-        PackageTreeItem* item = new PackageTreeItem( itemData, parent );
-
-        if ( itemDefinition[ "selected" ] )
+        QVariantMap groupMap = group.toMap();
+        if ( groupMap.isEmpty() )
         {
-            item->setSelected( getBool( itemDefinition, "selected" ) ? Qt::Checked : Qt::Unchecked );
-        }
-        else
-        {
-            item->setSelected( parent->isSelected() );  // Inherit from it's parent
+            continue;
         }
 
-        if ( itemDefinition[ "packages" ] )
+        PackageTreeItem* item = new PackageTreeItem( groupMap, parent );
+        if ( groupMap.contains( "selected" ) )
         {
-            for ( YAML::const_iterator packageIt = itemDefinition[ "packages" ].begin();
-                  packageIt != itemDefinition[ "packages" ].end();
-                  ++packageIt )
+            item->setSelected( CalamaresUtils::getBool( groupMap, "selected", false ) ? Qt::Checked : Qt::Unchecked );
+        }
+        if ( groupMap.contains( "packages" ) )
+        {
+            for ( const auto& packageName : groupMap.value( "packages" ).toStringList() )
             {
-                item->appendChild(
-                    new PackageTreeItem( CalamaresUtils::yamlToVariant( *packageIt ).toString(), item ) );
+                item->appendChild( new PackageTreeItem( packageName, item ) );
             }
         }
-        if ( itemDefinition[ "subgroups" ] )
+        if ( groupMap.contains( "subgroups" ) )
         {
-            setupModelData( itemDefinition[ "subgroups" ], item );
+            QVariantList subgroups = groupMap.value( "subgroups" ).toList();
+            if ( !subgroups.isEmpty() )
+            {
+                setupModelData( subgroups, item );
+                // The children might be checked while the parent isn't (yet).
+                // Children are added to their parent (below) without affecting
+                // the checked-state -- do it manually.
+                item->updateSelected();
+            }
         }
-
         if ( item->isHidden() )
         {
             m_hiddenItems.append( item );
@@ -283,3 +267,13 @@ PackageModel::setupModelData( const YAML::Node& data, PackageTreeItem* parent )
         }
     }
 }
+
+void
+PackageModel::setupModelData( const QVariantList& l )
+{
+    emit beginResetModel();
+    delete m_rootItem;
+    m_rootItem = new PackageTreeItem();
+    setupModelData( l, m_rootItem );
+    emit endResetModel();
+}
diff --git a/src/modules/netinstall/PackageModel.h b/src/modules/netinstall/PackageModel.h
index b76a58a42..b4e8fc102 100644
--- a/src/modules/netinstall/PackageModel.h
+++ b/src/modules/netinstall/PackageModel.h
@@ -37,8 +37,6 @@ class PackageModel : public QAbstractItemModel
     Q_OBJECT
 
 public:
-    using PackageItemDataList = QList< PackageTreeItem::ItemData >;
-
     // Names for columns (unused in the code)
     static constexpr const int NameColumn = 0;
     static constexpr const int DescriptionColumn = 1;
@@ -49,9 +47,11 @@ public:
      */
     static constexpr const int MetaExpandRole = Qt::UserRole + 1;
 
-    explicit PackageModel( const YAML::Node& data, QObject* parent = nullptr );
+    explicit PackageModel( QObject* parent = nullptr );
     ~PackageModel() override;
 
+    void setupModelData( const QVariantList& l );
+
     QVariant data( const QModelIndex& index, int role ) const override;
     bool setData( const QModelIndex& index, const QVariant& value, int role = Qt::EditRole ) override;
     Qt::ItemFlags flags( const QModelIndex& index ) const override;
@@ -63,14 +63,16 @@ public:
     int rowCount( const QModelIndex& parent = QModelIndex() ) const override;
     int columnCount( const QModelIndex& parent = QModelIndex() ) const override;
 
-    PackageItemDataList getPackages() const;
-    QList< PackageTreeItem* > getItemPackages( PackageTreeItem* item ) const;
+    PackageTreeItem::List getPackages() const;
+    PackageTreeItem::List getItemPackages( PackageTreeItem* item ) const;
 
 private:
-    void setupModelData( const YAML::Node& data, PackageTreeItem* parent );
+    friend class ItemTests;
 
-    PackageTreeItem* m_rootItem;
-    QList< PackageTreeItem* > m_hiddenItems;
+    void setupModelData( const QVariantList& l, PackageTreeItem* parent );
+
+    PackageTreeItem* m_rootItem = nullptr;
+    PackageTreeItem::List m_hiddenItems;
 };
 
 #endif  // PACKAGEMODEL_H
diff --git a/src/modules/netinstall/PackageTreeItem.cpp b/src/modules/netinstall/PackageTreeItem.cpp
index 7e20d63e1..edc89c536 100644
--- a/src/modules/netinstall/PackageTreeItem.cpp
+++ b/src/modules/netinstall/PackageTreeItem.cpp
@@ -20,56 +20,68 @@
 #include "PackageTreeItem.h"
 
 #include "utils/Logger.h"
+#include "utils/Variant.h"
 
-QVariant
-PackageTreeItem::ItemData::toOperation() const
+/** @brief Should a package be selected, given its parent's state? */
+static Qt::CheckState
+parentCheckState( PackageTreeItem* parent )
 {
-    // If it's a package with a pre- or post-script, replace
-    // with the more complicated datastructure.
-    if ( !preScript.isEmpty() || !postScript.isEmpty() )
+    if ( parent )
     {
-        QMap< QString, QVariant > sdetails;
-        sdetails.insert( "pre-script", preScript );
-        sdetails.insert( "package", packageName );
-        sdetails.insert( "post-script", postScript );
-        return sdetails;
+        // Avoid partially-checked .. a package can't be partial
+        return parent->isSelected() == Qt::Unchecked ? Qt::Unchecked : Qt::Checked;
     }
     else
     {
-        return packageName;
+        return Qt::Unchecked;
     }
 }
 
-PackageTreeItem::PackageTreeItem( const ItemData& data, PackageTreeItem* parent )
+/** @brief Should a subgroup be marked critical?
+ *
+ * If set explicitly, then use that, otherwise use the parent's critical-ness.
+ */
+static bool
+parentCriticality( const QVariantMap& groupData, PackageTreeItem* parent )
+{
+    if ( groupData.contains( "critical" ) )
+    {
+        return CalamaresUtils::getBool( groupData, "critical", false );
+    }
+    return parent ? parent->isCritical() : false;
+}
+
+PackageTreeItem::PackageTreeItem( const QString& packageName, PackageTreeItem* parent )
     : m_parentItem( parent )
-    , m_data( data )
+    , m_packageName( packageName )
+    , m_selected( parentCheckState( parent ) )
+    , m_isGroup( false )
+    , m_isCritical( parent ? parent->isCritical() : false )
+    , m_showReadOnly( parent ? parent->isImmutable() : false )
 {
 }
 
-PackageTreeItem::PackageTreeItem( const QString packageName, PackageTreeItem* parent )
-    : m_parentItem( parent )
-{
-    m_data.packageName = packageName;
-    if ( parent != nullptr )
-    {
-        m_data.selected = parent->isSelected();
-    }
-    else
-    {
-        m_data.selected = Qt::Unchecked;
-    }
-}
-
-PackageTreeItem::PackageTreeItem( PackageTreeItem* parent )
+PackageTreeItem::PackageTreeItem( const QVariantMap& groupData, PackageTreeItem* parent )
     : m_parentItem( parent )
+    , m_name( CalamaresUtils::getString( groupData, "name" ) )
+    , m_selected( parentCheckState( parent ) )
+    , m_description( CalamaresUtils::getString( groupData, "description" ) )
+    , m_preScript( CalamaresUtils::getString( groupData, "pre-install" ) )
+    , m_postScript( CalamaresUtils::getString( groupData, "post-install" ) )
+    , m_isGroup( true )
+    , m_isCritical( parentCriticality( groupData, parent ) )
+    , m_isHidden( CalamaresUtils::getBool( groupData, "hidden", false ) )
+    , m_showReadOnly( CalamaresUtils::getBool( groupData, "immutable", false ) )
+    , m_startExpanded( CalamaresUtils::getBool( groupData, "expanded", false ) )
 {
 }
 
 PackageTreeItem::PackageTreeItem::PackageTreeItem()
-    : PackageTreeItem( QString(), nullptr )
+    : m_parentItem( nullptr )
+    , m_name( QStringLiteral( "<root>" ) )
+    , m_selected( Qt::Checked )
+    , m_isGroup( true )
 {
-    m_data.selected = Qt::Checked;
-    m_data.name = QLatin1String( "<root>" );
 }
 
 PackageTreeItem::~PackageTreeItem()
@@ -108,7 +120,7 @@ PackageTreeItem::row() const
 QVariant
 PackageTreeItem::data( int column ) const
 {
-    if ( !packageName().isEmpty() )  // packages have a packagename, groups don't
+    if ( isPackage() )  // packages have a packagename, groups don't
     {
         switch ( column )
         {
@@ -123,7 +135,7 @@ PackageTreeItem::data( int column ) const
         switch ( column )  // group
         {
         case 0:
-            return QVariant( prettyName() );
+            return QVariant( name() );
         case 1:
             return QVariant( description() );
         default:
@@ -145,47 +157,15 @@ PackageTreeItem::parentItem() const
 }
 
 
-QString
-PackageTreeItem::prettyName() const
-{
-    return m_data.name;
-}
-
-QString
-PackageTreeItem::description() const
-{
-    return m_data.description;
-}
-
-QString
-PackageTreeItem::preScript() const
-{
-    return m_data.preScript;
-}
-
-QString
-PackageTreeItem::packageName() const
-{
-    return m_data.packageName;
-}
-
-QString
-PackageTreeItem::postScript() const
-{
-    return m_data.postScript;
-}
-
-bool
-PackageTreeItem::isHidden() const
-{
-    return m_data.isHidden;
-}
-
 bool
 PackageTreeItem::hiddenSelected() const
 {
-    Q_ASSERT( m_data.isHidden );
-    if ( !m_data.selected )
+    if ( !m_isHidden )
+    {
+        return m_selected != Qt::Unchecked;
+    }
+
+    if ( m_selected == Qt::Unchecked )
     {
         return false;
     }
@@ -200,33 +180,21 @@ PackageTreeItem::hiddenSelected() const
         currentItem = currentItem->parentItem();
     }
 
-    /* Has no non-hiddent parents */
-    return m_data.selected;
+    /* Has no non-hidden parents */
+    return m_selected != Qt::Unchecked;
 }
 
 
-bool
-PackageTreeItem::isCritical() const
-{
-    return m_data.isCritical;
-}
-
-Qt::CheckState
-PackageTreeItem::isSelected() const
-{
-    return m_data.selected;
-}
-
 void
 PackageTreeItem::setSelected( Qt::CheckState isSelected )
 {
     if ( parentItem() == nullptr )
-    // This is the root, it is always checked so don't change state
     {
+        // This is the root, it is always checked so don't change state
         return;
     }
 
-    m_data.selected = isSelected;
+    m_selected = isSelected;
     setChildrenSelected( isSelected );
 
     // Look for suitable parent item which may change checked-state
@@ -237,39 +205,46 @@ PackageTreeItem::setSelected( Qt::CheckState isSelected )
         currentItem = currentItem->parentItem();
     }
     if ( currentItem == nullptr )
-    // Reached the root .. don't bother
     {
+        // Reached the root .. don't bother
         return;
     }
 
+    currentItem->updateSelected();
+}
+
+void
+PackageTreeItem::updateSelected()
+{
     // Figure out checked-state based on the children
     int childrenSelected = 0;
     int childrenPartiallySelected = 0;
-    for ( int i = 0; i < currentItem->childCount(); i++ )
+    for ( int i = 0; i < childCount(); i++ )
     {
-        if ( currentItem->child( i )->isSelected() == Qt::Checked )
+        if ( child( i )->isSelected() == Qt::Checked )
         {
             childrenSelected++;
         }
-        if ( currentItem->child( i )->isSelected() == Qt::PartiallyChecked )
+        if ( child( i )->isSelected() == Qt::PartiallyChecked )
         {
             childrenPartiallySelected++;
         }
     }
     if ( !childrenSelected && !childrenPartiallySelected )
     {
-        currentItem->setSelected( Qt::Unchecked );
+        setSelected( Qt::Unchecked );
     }
-    else if ( childrenSelected == currentItem->childCount() )
+    else if ( childrenSelected == childCount() )
     {
-        currentItem->setSelected( Qt::Checked );
+        setSelected( Qt::Checked );
     }
     else
     {
-        currentItem->setSelected( Qt::PartiallyChecked );
+        setSelected( Qt::PartiallyChecked );
     }
 }
 
+
 void
 PackageTreeItem::setChildrenSelected( Qt::CheckState isSelected )
 {
@@ -277,7 +252,7 @@ PackageTreeItem::setChildrenSelected( Qt::CheckState isSelected )
         // Children are never root; don't need to use setSelected on them.
         for ( auto child : m_childItems )
         {
-            child->m_data.selected = isSelected;
+            child->m_selected = isSelected;
             child->setChildrenSelected( isSelected );
         }
 }
@@ -287,3 +262,43 @@ PackageTreeItem::type() const
 {
     return QStandardItem::UserType;
 }
+
+QVariant
+PackageTreeItem::toOperation() const
+{
+    // If it's a package with a pre- or post-script, replace
+    // with the more complicated datastructure.
+    if ( !m_preScript.isEmpty() || !m_postScript.isEmpty() )
+    {
+        QMap< QString, QVariant > sdetails;
+        sdetails.insert( "pre-script", m_preScript );
+        sdetails.insert( "package", m_packageName );
+        sdetails.insert( "post-script", m_postScript );
+        return sdetails;
+    }
+    else
+    {
+        return m_packageName;
+    }
+}
+
+bool
+PackageTreeItem::operator==( const PackageTreeItem& rhs ) const
+{
+    if ( isGroup() != rhs.isGroup() )
+    {
+        // Different kinds
+        return false;
+    }
+
+    if ( isGroup() )
+    {
+        return name() == rhs.name() && description() == rhs.description() && preScript() == rhs.preScript()
+            && postScript() == rhs.postScript() && isCritical() == rhs.isCritical() && isHidden() == rhs.isHidden()
+            && m_showReadOnly == rhs.m_showReadOnly && expandOnStart() == rhs.expandOnStart();
+    }
+    else
+    {
+        return packageName() == rhs.packageName();
+    }
+}
diff --git a/src/modules/netinstall/PackageTreeItem.h b/src/modules/netinstall/PackageTreeItem.h
index d9c1f9ec2..d443bcdc6 100644
--- a/src/modules/netinstall/PackageTreeItem.h
+++ b/src/modules/netinstall/PackageTreeItem.h
@@ -27,29 +27,14 @@
 class PackageTreeItem : public QStandardItem
 {
 public:
-    struct ItemData
-    {
-        QString name;
-        QString description;
-        QString preScript;
-        QString packageName;
-        QString postScript;
-        bool isCritical = false;
-        bool isHidden = false;
-        bool startExpanded = false;  // Only for groups
-        Qt::CheckState selected = Qt::Unchecked;
+    using List = QList< PackageTreeItem* >;
 
-        /** @brief Turns this item into a variant for PackageOperations use
-         *
-         * For "plain" items, this is just the package name; items with
-         * scripts return a map. See the package module for how it's interpreted.
-         */
-        QVariant toOperation() const;
-    };
-    explicit PackageTreeItem( const ItemData& data, PackageTreeItem* parent = nullptr );
-    explicit PackageTreeItem( const QString packageName, PackageTreeItem* parent = nullptr );
-    explicit PackageTreeItem( PackageTreeItem* parent );
-    explicit PackageTreeItem();  // The root of the tree; always selected, named <root>
+    ///@brief A package (individual package)
+    explicit PackageTreeItem( const QString& packageName, PackageTreeItem* parent = nullptr );
+    ///@brief A group (sub-items and sub-groups are ignored)
+    explicit PackageTreeItem( const QVariantMap& groupData, PackageTreeItem* parent = nullptr );
+    ///@brief A root item, always selected, named "<root>"
+    explicit PackageTreeItem();
     ~PackageTreeItem() override;
 
     void appendChild( PackageTreeItem* child );
@@ -61,18 +46,33 @@ public:
     PackageTreeItem* parentItem();
     const PackageTreeItem* parentItem() const;
 
-    QString prettyName() const;
-    QString description() const;
-    QString preScript() const;
-    QString packageName() const;
-    QString postScript() const;
+    QString name() const { return m_name; }
+    QString packageName() const { return m_packageName; }
+
+    QString description() const { return m_description; }
+    QString preScript() const { return m_preScript; }
+    QString postScript() const { return m_postScript; }
+
+    /** @brief Is this item a group-item?
+     *
+     * Groups have a (possibly empty) list of packages, and a
+     * (possibly empty) list of sub-groups, and can be marked
+     * critical, hidden, etc. Packages, on the other hand, only
+     * have a meaningful packageName() and selection status.
+     *
+     * Root is a group.
+     */
+    bool isGroup() const { return m_isGroup; }
+
+    /// @brief Is this item a single package?
+    bool isPackage() const { return !isGroup(); }
 
     /** @brief Is this item hidden?
      *
      * Hidden items (generally only groups) are maintained separately,
      * not shown to the user, but do enter into the package-installation process.
      */
-    bool isHidden() const;
+    bool isHidden() const { return m_isHidden; }
 
     /** @brief Is this hidden item, considered "selected"?
      *
@@ -87,7 +87,7 @@ public:
      * A critical group must be successfully installed, for the Calamares
      * installation to continue.
      */
-    bool isCritical() const;
+    bool isCritical() const { return m_isCritical; }
 
     /** @brief Is this group expanded on start?
      *
@@ -95,17 +95,69 @@ public:
      * that expands on start is shown expanded (not collapsed)
      * in the treeview when the page is loaded.
      */
-    bool expandOnStart() const { return m_data.startExpanded; }
+    bool expandOnStart() const { return m_startExpanded; }
+
+    /** @brief Is this an immutable item?
+     *
+     * Groups can be immutable: then you can't toggle the selected
+     * state of any of its items.
+     */
+    bool isImmutable() const { return m_showReadOnly; }
+
+    /** @brief is this item selected?
+     *
+     * Groups may be partially selected; packages are only on or off.
+     */
+    Qt::CheckState isSelected() const { return m_selected; }
+
+    /** @brief Turns this item into a variant for PackageOperations use
+     *
+     * For "plain" items, this is just the package name; items with
+     * scripts return a map. See the package module for how it's interpreted.
+     */
+    QVariant toOperation() const;
 
-    Qt::CheckState isSelected() const;
     void setSelected( Qt::CheckState isSelected );
     void setChildrenSelected( Qt::CheckState isSelected );
+
+    /** @brief Update selectedness based on the children's states
+     *
+     * This only makes sense for groups, which might have packages
+     * or subgroups; it checks only direct children.
+     */
+    void updateSelected();
+
+    // QStandardItem methods
     int type() const override;
 
+    /** @brief Are two items equal
+     *
+     * This **disregards** parent-item and the child-items, and compares
+     * only the fields for the items-proper (name, .. expanded). Note
+     * also that *isSelected()* is a run-time state, and is **not**
+     * compared either.
+     */
+    bool operator==( const PackageTreeItem& rhs ) const;
+    bool operator!=( const PackageTreeItem& rhs ) const { return !( *this == rhs ); }
+
 private:
     PackageTreeItem* m_parentItem;
-    QList< PackageTreeItem* > m_childItems;
-    ItemData m_data;
+    List m_childItems;
+
+    // An entry can be a package, or a group.
+    QString m_name;
+    QString m_packageName;
+    Qt::CheckState m_selected = Qt::Unchecked;
+
+    // These are only useful for groups
+    QString m_description;
+    QString m_preScript;
+    QString m_postScript;
+    bool m_isGroup = false;
+    bool m_isCritical = false;
+    bool m_isHidden = false;
+    bool m_showReadOnly = false;
+    bool m_startExpanded = false;
 };
 
 #endif  // PACKAGETREEITEM_H
diff --git a/src/modules/netinstall/README.md b/src/modules/netinstall/README.md
index a8803edd5..cda4b6c88 100644
--- a/src/modules/netinstall/README.md
+++ b/src/modules/netinstall/README.md
@@ -48,8 +48,12 @@ More keys (per group) are supported:
  - *critical*: if true, make the installation process fail if installing
    any of the packages in the group fails. Otherwise, just log a warning.
    Defaults to false.
+ - *immutable*: if true, the state of the group (and all its subgroups)
+   cannot be changed; it really only makes sense in combination
+   with *selected* set to true. This only affects the user-interface.
  - *expanded*: if true, the group is shown in an expanded form (that is,
-   not-collapsed) in the treeview on start.
+   not-collapsed) in the treeview on start. This only affects the user-
+   interface.
  - *subgroups*: if present this follows the same structure as the top level
    of the YAML file, allowing there to be sub-groups of packages to an
    arbitary depth
diff --git a/src/modules/netinstall/Tests.cpp b/src/modules/netinstall/Tests.cpp
new file mode 100644
index 000000000..cfaf20efa
--- /dev/null
+++ b/src/modules/netinstall/Tests.cpp
@@ -0,0 +1,310 @@
+/* === This file is part of Calamares - <https://github.com/calamares> ===
+ *
+ *   Copyright 2020, Adriaan de Groot <groot@kde.org>
+ *
+ *   Calamares is free software: you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation, either version 3 of the License, or
+ *   (at your option) any later version.
+ *
+ *   Calamares is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with Calamares. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "PackageModel.h"
+#include "PackageTreeItem.h"
+
+#include "utils/Logger.h"
+#include "utils/Variant.h"
+#include "utils/Yaml.h"
+
+#include <QtTest/QtTest>
+
+class ItemTests : public QObject
+{
+    Q_OBJECT
+public:
+    ItemTests();
+    virtual ~ItemTests() {}
+
+private:
+    void checkAllSelected( PackageTreeItem* p );
+    void recursiveCompare( PackageTreeItem*, PackageTreeItem* );
+    void recursiveCompare( PackageModel&, PackageModel& );
+
+private Q_SLOTS:
+    void initTestCase();
+
+    void testRoot();
+    void testPackage();
+    void testGroup();
+    void testCompare();
+    void testModel();
+    void testExampleFiles();
+};
+
+ItemTests::ItemTests() {}
+
+void
+ItemTests::initTestCase()
+{
+    Logger::setupLogLevel( Logger::LOGDEBUG );
+}
+
+void
+ItemTests::testRoot()
+{
+    PackageTreeItem r;
+
+    QCOMPARE( r.isSelected(), Qt::Checked );
+    QCOMPARE( r.name(), QStringLiteral( "<root>" ) );
+    QCOMPARE( r.parentItem(), nullptr );
+    QVERIFY( r.isGroup() );
+
+    QVERIFY( r == r );
+}
+
+void
+ItemTests::testPackage()
+{
+    PackageTreeItem p( "bash", nullptr );
+
+    QCOMPARE( p.isSelected(), Qt::Unchecked );
+    QCOMPARE( p.packageName(), QStringLiteral( "bash" ) );
+    QVERIFY( p.name().isEmpty() );  // not a group
+    QCOMPARE( p.parentItem(), nullptr );
+    QCOMPARE( p.childCount(), 0 );
+    QVERIFY( !p.isHidden() );
+    QVERIFY( !p.isCritical() );
+    QVERIFY( !p.isGroup() );
+    QVERIFY( p.isPackage() );
+    QVERIFY( p == p );
+
+    // This doesn't happen in normal constructions,
+    // because a package can't have children.
+    PackageTreeItem c( "zsh", &p );
+    QCOMPARE( c.isSelected(), Qt::Unchecked );
+    QCOMPARE( c.packageName(), QStringLiteral( "zsh" ) );
+    QVERIFY( c.name().isEmpty() );  // not a group
+    QCOMPARE( c.parentItem(), &p );
+    QVERIFY( !c.isGroup() );
+    QVERIFY( c.isPackage() );
+    QVERIFY( c == c );
+    QVERIFY( c != p );
+
+    QCOMPARE( p.childCount(), 0 );  // not noticed it has a child
+}
+
+// *INDENT-OFF*
+// clang-format off
+static const char doc[] =
+"- name: \"CCR\"\n"
+"  description: \"Tools for the Chakra Community Repository\"\n"
+"  packages:\n"
+"    - ccr\n"
+"    - base-devel\n"
+"    - bash\n";
+
+static const char doc_no_packages[] =
+"- name: \"CCR\"\n"
+"  description: \"Tools for the Chakra Community Repository\"\n"
+"  packages: []\n";
+
+static const char doc_with_expanded[] =
+"- name: \"CCR\"\n"
+"  description: \"Tools for the Chakra Community Repository\"\n"
+"  expanded: true\n"
+"  packages:\n"
+"    - ccr\n"
+"    - base-devel\n"
+"    - bash\n";
+// *INDENT-ON*
+// clang-format on
+
+void
+ItemTests::testGroup()
+{
+    YAML::Node yamldoc = YAML::Load( doc );
+    QVariantList yamlContents = CalamaresUtils::yamlSequenceToVariant( yamldoc );
+
+    QCOMPARE( yamlContents.length(), 1 );
+
+    PackageTreeItem p( yamlContents[ 0 ].toMap(), nullptr );
+    QCOMPARE( p.name(), QStringLiteral( "CCR" ) );
+    QVERIFY( p.packageName().isEmpty() );
+    QVERIFY( p.description().startsWith( QStringLiteral( "Tools " ) ) );
+    QCOMPARE( p.parentItem(), nullptr );
+    QVERIFY( !p.isHidden() );
+    QVERIFY( !p.isCritical() );
+    // The item-constructor doesn't consider the packages: list
+    QCOMPARE( p.childCount(), 0 );
+    QVERIFY( p.isGroup() );
+    QVERIFY( !p.isPackage() );
+    QVERIFY( p == p );
+
+    PackageTreeItem c( "zsh", nullptr );
+    QVERIFY( p != c );
+}
+
+void
+ItemTests::testCompare()
+{
+    PackageTreeItem p0( "bash", nullptr );
+    PackageTreeItem p1( "bash", &p0 );
+    PackageTreeItem p2( "bash", nullptr );
+
+    QVERIFY( p0 == p1 );  // Parent doesn't matter
+    QVERIFY( p0 == p2 );
+
+    p2.setSelected( Qt::Checked );
+    p1.setSelected( Qt::Unchecked );
+    QVERIFY( p0 == p1 );  // Neither does selected state
+    QVERIFY( p0 == p2 );
+
+    PackageTreeItem r0( nullptr );
+    QVERIFY( p0 != r0 );
+    QVERIFY( p1 != r0 );
+    QVERIFY( r0 == r0 );
+    PackageTreeItem r1( nullptr );
+    QVERIFY( r0 == r1 );  // Different roots are still equal
+
+    PackageTreeItem r2( "<root>", nullptr );  // Fake root
+    QVERIFY( r0 != r2 );
+    QVERIFY( r1 != r2 );
+    QVERIFY( p0 != r2 );
+    PackageTreeItem r3( "<root>", nullptr );
+    QVERIFY( r3 == r2 );
+
+    YAML::Node yamldoc = YAML::Load( doc );  // See testGroup()
+    QVariantList yamlContents = CalamaresUtils::yamlSequenceToVariant( yamldoc );
+    QCOMPARE( yamlContents.length(), 1 );
+
+    PackageTreeItem p3( yamlContents[ 0 ].toMap(), nullptr );
+    QVERIFY( p3 == p3 );
+    QVERIFY( p3 != p1 );
+    QVERIFY( p1 != p3 );
+    QCOMPARE( p3.childCount(), 0 );  // Doesn't load the packages: list
+
+    PackageTreeItem p4( CalamaresUtils::yamlSequenceToVariant( YAML::Load( doc ) )[ 0 ].toMap(), nullptr );
+    QVERIFY( p3 == p4 );
+    PackageTreeItem p5( CalamaresUtils::yamlSequenceToVariant( YAML::Load( doc_no_packages ) )[ 0 ].toMap(), nullptr );
+    QVERIFY( p3 == p5 );
+}
+
+void
+ItemTests::checkAllSelected( PackageTreeItem* p )
+{
+    QVERIFY( p->isSelected() );
+    for ( int i = 0; i < p->childCount(); ++i )
+    {
+        checkAllSelected( p->child( i ) );
+    }
+}
+
+void
+ItemTests::recursiveCompare( PackageTreeItem* l, PackageTreeItem* r )
+{
+    QVERIFY( l && r );
+    QVERIFY( *l == *r );
+    QCOMPARE( l->childCount(), r->childCount() );
+
+    for ( int i = 0; i < l->childCount(); ++i )
+    {
+        QCOMPARE( l->childCount(), r->childCount() );
+        recursiveCompare( l->child( i ), r->child( i ) );
+    }
+}
+
+void
+ItemTests::recursiveCompare( PackageModel& l, PackageModel& r )
+{
+    return recursiveCompare( l.m_rootItem, r.m_rootItem );
+}
+
+
+void
+ItemTests::testModel()
+{
+    YAML::Node yamldoc = YAML::Load( doc );  // See testGroup()
+    QVariantList yamlContents = CalamaresUtils::yamlSequenceToVariant( yamldoc );
+    QCOMPARE( yamlContents.length(), 1 );
+
+    PackageModel m0( nullptr );
+    m0.setupModelData( yamlContents );
+
+    QCOMPARE( m0.m_hiddenItems.count(), 0 );  // Nothing hidden
+    QCOMPARE( m0.rowCount(), 1 );  // Group, the packages are invisible
+    QCOMPARE( m0.rowCount( m0.index( 0, 0 ) ), 3 );  // The packages
+
+    checkAllSelected( m0.m_rootItem );
+
+    PackageModel m2( nullptr );
+    m2.setupModelData( CalamaresUtils::yamlSequenceToVariant( YAML::Load( doc_with_expanded ) ) );
+    QCOMPARE( m2.m_hiddenItems.count(), 0 );
+    QCOMPARE( m2.rowCount(), 1 );  // Group, now the packages expanded but not counted
+    QCOMPARE( m2.rowCount( m2.index( 0, 0 ) ), 3 );  // The packages
+    checkAllSelected( m2.m_rootItem );
+
+    PackageTreeItem r;
+    QVERIFY( r == *m0.m_rootItem );
+
+    QCOMPARE( m0.m_rootItem->childCount(), 1 );
+
+    PackageTreeItem* group = m0.m_rootItem->child( 0 );
+    QVERIFY( group->isGroup() );
+    QCOMPARE( group->name(), QStringLiteral( "CCR" ) );
+    QCOMPARE( group->childCount(), 3 );
+
+    PackageTreeItem bash( "bash", nullptr );
+    // Check that the sub-packages loaded correctly
+    bool found_one_bash = false;
+    for ( int i = 0; i < group->childCount(); ++i )
+    {
+        QVERIFY( group->child( i )->isPackage() );
+        if ( bash == *( group->child( i ) ) )
+        {
+            found_one_bash = true;
+        }
+    }
+    QVERIFY( found_one_bash );
+
+    // But m2 has "expanded" set which the others do no
+    QVERIFY( *( m2.m_rootItem->child( 0 ) ) != *group );
+}
+
+void
+ItemTests::testExampleFiles()
+{
+    QVERIFY( QStringLiteral( BUILD_AS_TEST ).endsWith( "/netinstall" ) );
+
+    QDir d( BUILD_AS_TEST );
+
+    for ( const QString& filename : QStringList { "netinstall.yaml" } )
+    {
+        QFile f( d.filePath( filename ) );
+        QVERIFY( f.exists() );
+        QVERIFY( f.open( QIODevice::ReadOnly ) );
+        QByteArray contents = f.readAll();
+        QVERIFY( !contents.isEmpty() );
+
+        YAML::Node yamldoc = YAML::Load( contents.constData() );
+        QVariantList yamlContents = CalamaresUtils::yamlSequenceToVariant( yamldoc );
+
+        PackageModel m1( nullptr );
+        m1.setupModelData( yamlContents );
+
+        // TODO: should test *something* about this file :/
+    }
+}
+
+
+QTEST_GUILESS_MAIN( ItemTests )
+
+#include "utils/moc-warnings.h"
+
+#include "Tests.moc"
diff --git a/src/modules/netinstall/netinstall.conf b/src/modules/netinstall/netinstall.conf
index 5f90fec76..82e12d558 100644
--- a/src/modules/netinstall/netinstall.conf
+++ b/src/modules/netinstall/netinstall.conf
@@ -11,7 +11,11 @@
 #
 # The format of the groups file is documented in `README.md`.
 #
-# groupsUrl: file:///usr/share/calamares/netinstall.yaml
+# As a special case, setting *groupsUrl* to the literal string
+# `local` means that the data is obtained from **this** config
+# file, under the key *groups*.
+#
+groupsUrl: local
 
 # If the installation can proceed without netinstall (e.g. the Live CD
 # can create a working installed system, but netinstall is preferred
@@ -46,3 +50,46 @@ label:
     # sidebar[nl]: "Pakketkeuze"
     # title: "Office Package"
     # title[nl]: "Kantoorsoftware"
+
+# If, and only if, *groupsUrl* is set to the literal string `local`,
+# groups data is read from this file. The value of *groups* must be
+# a list, with the same format as the regular `netinstall.yaml` file.
+#
+# This is recommended only for small static package lists.
+groups:
+    - name: "Default"
+      description: "Default group"
+      hidden: true
+      selected: true
+      critical: false
+      packages:
+        - base
+        - chakra-live-skel
+    - name: "Shells"
+      description: "Shells"
+      hidden: false
+      selected: false
+      critical: true
+      subgroups:
+        - name: "Bash"
+          description: "Bourne Again Shell"
+          selected: true
+          packages:
+            - bash
+            - bash-completion
+        - name: "Zsh"
+          description: "Zee shell, boss"
+          packages:
+            - zsh
+            - zsh-completion
+            - zsh-extensions
+    - name: "Kernel"
+      description: "Kernel bits"
+      hidden: false
+      selected: true
+      critical: true
+      immutable: true
+      packages:
+        - kernel
+        - kernel-debugsym
+        - kernel-nvidia