diff --git a/src/akonadi/akonadicachingstorage.h b/src/akonadi/akonadicachingstorage.h
--- a/src/akonadi/akonadicachingstorage.h
+++ b/src/akonadi/akonadicachingstorage.h
@@ -51,10 +51,6 @@
 
     KJob *createTransaction() override;
 
-    KJob *createTag(Akonadi::Tag tag) override;
-    KJob *updateTag(Akonadi::Tag tag) override;
-    KJob *removeTag(Akonadi::Tag tag) override;
-
     CollectionFetchJobInterface *fetchCollections(Akonadi::Collection collection, FetchDepth depth) override;
     ItemFetchJobInterface *fetchItems(Akonadi::Collection collection) override;
     ItemFetchJobInterface *fetchItem(Akonadi::Item item) override;
diff --git a/src/akonadi/akonadicachingstorage.cpp b/src/akonadi/akonadicachingstorage.cpp
--- a/src/akonadi/akonadicachingstorage.cpp
+++ b/src/akonadi/akonadicachingstorage.cpp
@@ -499,21 +499,6 @@
     return m_storage->createTransaction();
 }
 
-KJob *CachingStorage::createTag(Tag tag)
-{
-    return m_storage->createTag(tag);
-}
-
-KJob *CachingStorage::updateTag(Tag tag)
-{
-    return m_storage->updateTag(tag);
-}
-
-KJob *CachingStorage::removeTag(Tag tag)
-{
-    return m_storage->removeTag(tag);
-}
-
 CollectionFetchJobInterface *CachingStorage::fetchCollections(Collection collection, StorageInterface::FetchDepth depth)
 {
     return new CachingCollectionFetchJob(m_storage, m_cache, collection, depth);
diff --git a/src/akonadi/akonadiserializer.cpp b/src/akonadi/akonadiserializer.cpp
--- a/src/akonadi/akonadiserializer.cpp
+++ b/src/akonadi/akonadiserializer.cpp
@@ -589,8 +589,10 @@
 
 void Serializer::addContextToTask(Domain::Context::Ptr context, Item item)
 {
-    if (!isTaskItem(item))
+    if (!isTaskItem(item)) {
+        qWarning() << "Cannot add context to a non-task" << item.id();
         return;
+    }
 
     auto todo = item.payload<KCalCore::Todo::Ptr>();
 
@@ -608,8 +610,10 @@
 
 void Serializer::removeContextFromTask(Domain::Context::Ptr context, Item item)
 {
-    if (!isTaskItem(item))
+    if (!isTaskItem(item)) {
+        qWarning() << "Cannot remove context from a non-task" << item.id();
         return;
+    }
 
     auto todo = item.payload<KCalCore::Todo::Ptr>();
 
diff --git a/src/akonadi/akonadistorage.h b/src/akonadi/akonadistorage.h
--- a/src/akonadi/akonadistorage.h
+++ b/src/akonadi/akonadistorage.h
@@ -52,10 +52,6 @@
 
     KJob *createTransaction() override;
 
-    KJob *createTag(Akonadi::Tag tag) override;
-    KJob *updateTag(Akonadi::Tag tag) override;
-    KJob *removeTag(Akonadi::Tag tag) override;
-
     CollectionFetchJobInterface *fetchCollections(Akonadi::Collection collection, FetchDepth depth) override;
     ItemFetchJobInterface *fetchItems(Akonadi::Collection collection) override;
     ItemFetchJobInterface *fetchItem(Akonadi::Item item) override;
diff --git a/src/akonadi/akonadistorage.cpp b/src/akonadi/akonadistorage.cpp
--- a/src/akonadi/akonadistorage.cpp
+++ b/src/akonadi/akonadistorage.cpp
@@ -39,11 +39,8 @@
 #include <AkonadiCore/ItemModifyJob>
 #include <AkonadiCore/ItemMoveJob>
 #include <AkonadiCore/TransactionSequence>
-#include <AkonadiCore/TagCreateJob>
-#include <AkonadiCore/TagDeleteJob>
 #include <AkonadiCore/TagFetchJob>
 #include <AkonadiCore/TagFetchScope>
-#include <AkonadiCore/TagModifyJob>
 #include <AkonadiCore/TagAttribute>
 #include "akonadi/akonadicollectionfetchjobinterface.h"
 #include "akonadi/akonadiitemfetchjobinterface.h"
@@ -208,21 +205,6 @@
     return new TransactionSequence();
 }
 
-KJob *Storage::createTag(Tag tag)
-{
-    return new TagCreateJob(tag);
-}
-
-KJob *Storage::updateTag(Tag tag)
-{
-    return new TagModifyJob(tag);
-}
-
-KJob *Storage::removeTag(Tag tag)
-{
-    return new Akonadi::TagDeleteJob(tag);
-}
-
 CollectionFetchJobInterface *Storage::fetchCollections(Collection collection, StorageInterface::FetchDepth depth)
 {
     auto job = new CollectionJob(collection, jobTypeFromDepth(depth));
diff --git a/src/akonadi/akonadistorageinterface.h b/src/akonadi/akonadistorageinterface.h
--- a/src/akonadi/akonadistorageinterface.h
+++ b/src/akonadi/akonadistorageinterface.h
@@ -69,10 +69,6 @@
 
     virtual KJob *createTransaction() = 0;
 
-    virtual KJob *createTag(Akonadi::Tag tag) = 0;
-    virtual KJob *updateTag(Akonadi::Tag tag) = 0;
-    virtual KJob *removeTag(Akonadi::Tag tag) = 0;
-
     virtual CollectionFetchJobInterface *fetchCollections(Akonadi::Collection collection, FetchDepth depth) = 0;
     virtual ItemFetchJobInterface *fetchItems(Akonadi::Collection collection) = 0;
     virtual ItemFetchJobInterface *fetchItem(Akonadi::Item item) = 0;
diff --git a/src/akonadi/akonaditagfetchjobinterface.h b/src/akonadi/akonaditagfetchjobinterface.h
deleted file mode 100644
--- a/src/akonadi/akonaditagfetchjobinterface.h
+++ /dev/null
@@ -1,48 +0,0 @@
-/* This file is part of Zanshin
-
-   Copyright 2014 Franck Arrecot <franck.arrecot@gmail.com>
-
-   This program 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 2 of
-   the License or (at your option) version 3 or any later version
-   accepted by the membership of KDE e.V. (or its successor approved
-   by the membership of KDE e.V.), which shall act as a proxy
-   defined in Section 14 of version 3 of the license.
-
-   This program 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 this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
-   USA.
-*/
-
-
-#ifndef AKONADI_TAGFETCHJOBINTERFACE_H
-#define AKONADI_TAGFETCHJOBINTERFACE_H
-
-#include <AkonadiCore/Tag>
-
-class KJob;
-
-namespace Akonadi {
-
-class TagFetchJobInterface
-{
-    public:
-        TagFetchJobInterface();
-        virtual ~TagFetchJobInterface();
-
-        KJob *kjob();
-
-        virtual Tag::List tags() const = 0;
-};
-
-} // Akonadi namespace
-
-
-#endif // AKONADI_TAGFETCHJOBINTERFACE_H
diff --git a/src/akonadi/akonaditagfetchjobinterface.cpp b/src/akonadi/akonaditagfetchjobinterface.cpp
deleted file mode 100644
--- a/src/akonadi/akonaditagfetchjobinterface.cpp
+++ /dev/null
@@ -1,44 +0,0 @@
-/* This file is part of Zanshin
-
-   Copyright 2014 Franck Arrecot <franck.arrecot@gmail.com>
-
-   This program 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 2 of
-   the License or (at your option) version 3 or any later version
-   accepted by the membership of KDE e.V. (or its successor approved
-   by the membership of KDE e.V.), which shall act as a proxy
-   defined in Section 14 of version 3 of the license.
-
-   This program 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 this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
-   USA.
-*/
-
-#include "akonaditagfetchjobinterface.h"
-#include <KJob>
-
-using namespace Akonadi ;
-
-TagFetchJobInterface::TagFetchJobInterface()
-{
-}
-
-TagFetchJobInterface::~TagFetchJobInterface()
-{
-}
-
-KJob *TagFetchJobInterface::kjob()
-{
-    KJob *job = dynamic_cast<KJob*>(this);
-    Q_ASSERT(job);
-    return job;
-}
-
-
diff --git a/tests/testlib/akonadifakedata.h b/tests/testlib/akonadifakedata.h
--- a/tests/testlib/akonadifakedata.h
+++ b/tests/testlib/akonadifakedata.h
@@ -28,7 +28,6 @@
 
 #include <AkonadiCore/Collection>
 #include <AkonadiCore/Item>
-#include <AkonadiCore/Tag>
 
 #include "testlib/akonadifakestoragebehavior.h"
 
@@ -57,15 +56,16 @@
     void modifyCollection(const Akonadi::Collection &collection);
     void removeCollection(const Akonadi::Collection &collection);
 
-    Akonadi::Tag::List tags() const;
-    Akonadi::Tag tag(Akonadi::Tag::Id id) const;
-    void createTag(const Akonadi::Tag &tag);
-    void modifyTag(const Akonadi::Tag &tag);
-    void removeTag(const Akonadi::Tag &tag);
+    QStringList contextsUids() const;
+    Akonadi::Item::List contexts() const;
+    Akonadi::Item contextItem(const QString &uid) const;
+    void createContext(const Akonadi::Item &item);
+    void modifyContext(const Akonadi::Item &item);
+    void removeContext(const Akonadi::Item &item);
 
     Akonadi::Item::List items() const;
     Akonadi::Item::List childItems(Akonadi::Collection::Id parentId) const;
-    Akonadi::Item::List tagItems(Akonadi::Tag::Id tagId) const;
+    Akonadi::Item::List contextItems(const QString& contextUid) const;
     Akonadi::Item item(Akonadi::Item::Id id) const;
     void createItem(const Akonadi::Item &item);
     void modifyItem(const Akonadi::Item &item);
@@ -76,7 +76,6 @@
 
     Akonadi::Collection::Id maxCollectionId() const;
     Akonadi::Item::Id maxItemId() const;
-    Akonadi::Tag::Id maxTagId() const;
 
     Akonadi::Collection reconstructAncestors(const Akonadi::Collection &collection,
                                              const Akonadi::Collection &root = Akonadi::Collection::root()) const;
@@ -90,11 +89,12 @@
     QHash<Akonadi::Collection::Id, Akonadi::Collection> m_collections;
     QHash<Akonadi::Collection::Id, QList<Akonadi::Collection::Id>> m_childCollections;
 
-    QHash<Akonadi::Tag::Id, Akonadi::Tag> m_tags;
+    using ContextUid = QString;
+    QHash<ContextUid, Akonadi::Item> m_contexts;
 
     QHash<Akonadi::Item::Id, Akonadi::Item> m_items;
     QHash<Akonadi::Collection::Id, QList<Akonadi::Item::Id>> m_childItems;
-    QHash<Akonadi::Tag::Id, QList<Akonadi::Item::Id>> m_tagItems;
+    QHash<ContextUid, QList<Akonadi::Item::Id>> m_contextItems;
 
     QScopedPointer<AkonadiFakeMonitor> m_monitor;
 
diff --git a/tests/testlib/akonadifakedata.cpp b/tests/testlib/akonadifakedata.cpp
--- a/tests/testlib/akonadifakedata.cpp
+++ b/tests/testlib/akonadifakedata.cpp
@@ -41,6 +41,51 @@
                             : Akonadi::Collection::root().id();
 }
 
+static const char s_contextListProperty[] = "ContextList";
+static const char s_appName[] = "Zanshin";
+
+// Should be in the serializer ideally ... but we don't link to that from here anyway.
+static QStringList extractContextUids(const Akonadi::Item &taskItem)
+{
+    if (!taskItem.hasPayload<KCalCore::Todo::Ptr>())
+        return {};
+    auto todo = taskItem.payload<KCalCore::Todo::Ptr>();
+    const QString contexts = todo->customProperty(s_appName, s_contextListProperty);
+    return contexts.split(',', QString::SkipEmptyParts);
+}
+
+// Duplicated from the serializer
+static QString contextUid(const Akonadi::Item &contextItem)
+{
+    auto contextTodo = contextItem.payload<KCalCore::Todo::Ptr>();
+    return contextTodo->uid();
+}
+
+// Somewhat duplicated from the serializer
+static void removeContextFromTask(const QString &contextUid, Akonadi::Item &item)
+{
+    auto todo = item.payload<KCalCore::Todo::Ptr>();
+    const QString contexts = todo->customProperty(s_appName, s_contextListProperty);
+    QStringList contextList = contexts.split(',', QString::SkipEmptyParts);
+    contextList.removeAll(contextUid);
+    if (contextList.isEmpty())
+        todo->removeCustomProperty(s_appName, s_contextListProperty);
+    else
+        todo->setCustomProperty(s_appName, s_contextListProperty, contextList.join(','));
+    item.setPayload<KCalCore::Todo::Ptr>(todo);
+    Q_ASSERT(contextList == extractContextUids(item));
+}
+
+// Duplicate from the serializer
+static bool isContext(const Akonadi::Item &item)
+{
+    if (!item.hasPayload<KCalCore::Todo::Ptr>())
+        return false;
+
+    auto todo = item.payload<KCalCore::Todo::Ptr>();
+    return !todo->customProperty(s_appName, "Context").isEmpty();
+}
+
 AkonadiFakeData::AkonadiFakeData()
     : m_monitor(new AkonadiFakeMonitor)
 {
@@ -170,53 +215,58 @@
     m_monitor->removeCollection(col);
 }
 
-Akonadi::Tag::List AkonadiFakeData::tags() const
+QStringList AkonadiFakeData::contextsUids() const
 {
-    return m_tags.values().toVector();
+    return m_contexts.keys();
 }
 
-Akonadi::Tag AkonadiFakeData::tag(Akonadi::Tag::Id id) const
+Akonadi::Item::List AkonadiFakeData::contexts() const
 {
-    if (!m_tags.contains(id))
-        return Akonadi::Tag();
+    return m_contexts.values().toVector();
+}
 
-    return m_tags.value(id);
+Akonadi::Item AkonadiFakeData::contextItem(const QString &uid) const
+{
+    return m_contexts.value(uid);
 }
 
-void AkonadiFakeData::createTag(const Akonadi::Tag &tag)
+void AkonadiFakeData::createContext(const Akonadi::Item &contextItem)
 {
-    Q_ASSERT(!m_tags.contains(tag.id()));
-    m_tags[tag.id()] = tag;
-    m_monitor->addTag(tag);
+    const QString uid = contextUid(contextItem);
+    Q_ASSERT(!m_contexts.contains(uid));
+    m_contexts[uid] = contextItem;
+    m_monitor->addItem(contextItem);
 }
 
-void AkonadiFakeData::modifyTag(const Akonadi::Tag &tag)
+void AkonadiFakeData::modifyContext(const Akonadi::Item &contextItem)
 {
-    Q_ASSERT(m_tags.contains(tag.id()));
-    const auto oldTag = m_tags.take(tag.id());
-    auto newTag = tag;
-    newTag.setGid(oldTag.gid());
-    newTag.setRemoteId(oldTag.remoteId());
-    m_tags[tag.id()] = newTag;
-    m_monitor->changeTag(newTag);
+    const QString uid = contextUid(contextItem);
+    Q_ASSERT(m_contexts.contains(uid));
+    const auto oldContextItem = m_contexts.take(uid);
+    auto newItem = contextItem;
+    newItem.setGid(oldContextItem.gid());
+    newItem.setRemoteId(oldContextItem.remoteId());
+    m_contexts[uid] = newItem;
+    m_monitor->changeItem(newItem);
 }
 
-void AkonadiFakeData::removeTag(const Akonadi::Tag &tag)
+void AkonadiFakeData::removeContext(const Akonadi::Item &contextItem)
 {
-    Q_ASSERT(m_tags.contains(tag.id()));
+    const QString uid = contextUid(contextItem);
+    Q_ASSERT(m_contexts.contains(uid));
 
-    const auto ids = m_tagItems[tag.id()];
+    const auto ids = m_contextItems[uid];
     foreach (const auto &id, ids) {
         Q_ASSERT(m_items.contains(id));
         auto item = m_items.value(id);
-        item.clearTag(tag);
+        removeContextFromTask(uid, item);
         m_items[id] = item;
         m_monitor->changeItem(item);
     }
-    m_tagItems.remove(tag.id());
+    m_contextItems.remove(uid);
 
-    m_tags.remove(tag.id());
-    m_monitor->removeTag(tag);
+    m_contexts.remove(uid);
+    m_monitor->removeItem(contextItem);
 }
 
 Akonadi::Item::List AkonadiFakeData::items() const
@@ -240,13 +290,11 @@
     return result;
 }
 
-Akonadi::Item::List AkonadiFakeData::tagItems(Akonadi::Tag::Id tagId) const
+Akonadi::Item::List AkonadiFakeData::contextItems(const QString &contextUid) const
 {
-    if (!m_tagItems.contains(tagId))
-        return {};
-
-    const auto ids = m_tagItems.value(tagId);
+    const auto ids = m_contextItems.value(contextUid);
     auto result = Akonadi::Item::List();
+    result.reserve(ids.size());
     std::transform(std::begin(ids), std::end(ids),
                    std::back_inserter(result),
                    [this] (Akonadi::Item::Id id) {
@@ -266,25 +314,33 @@
 
 void AkonadiFakeData::createItem(const Akonadi::Item &item)
 {
+    Q_ASSERT(item.isValid());
     Q_ASSERT(!m_items.contains(item.id()));
     m_items[item.id()] = item;
 
     const auto parentId = findParentId(item);
     m_childItems[parentId] << item.id();
 
-    foreach (const auto &tag, item.tags()) {
-        Q_ASSERT(m_tags.contains(tag.id()));
-        m_tagItems[tag.id()] << item.id();
+    const QStringList contextUids = extractContextUids(item);
+    foreach (const auto &contextUid, contextUids) {
+        Q_ASSERT(m_contexts.contains(contextUid));
+        m_contextItems[contextUid] << item.id();
     }
 
-    m_monitor->addItem(reconstructItemDependencies(item));
+    if (isContext(item)) {
+        createContext(item);
+    } else {
+        m_monitor->addItem(reconstructItemDependencies(item));
+    }
 }
 
 void AkonadiFakeData::modifyItem(const Akonadi::Item &item)
 {
     Q_ASSERT(m_items.contains(item.id()));
+    Q_ASSERT(item.isValid());
 
-    const auto oldTags = m_items[item.id()].tags();
+    const auto oldContexts = extractContextUids(m_items[item.id()]);
+    const auto newContexts = extractContextUids(item);
     const auto oldParentId = findParentId(m_items[item.id()]);
     const auto oldItem = m_items.take(item.id());
     auto newItem = item;
@@ -301,30 +357,39 @@
         m_monitor->moveItem(reconstructItemDependencies(newItem));
     }
 
-    foreach (const auto &tag, oldTags) {
-        m_tagItems[tag.id()].removeAll(newItem.id());
+    foreach (const auto &contextUid, oldContexts) {
+        m_contextItems[contextUid].removeAll(newItem.id());
     }
 
-    foreach (const auto &tag, newItem.tags()) {
-        Q_ASSERT(m_tags.contains(tag.id()));
-        m_tagItems[tag.id()] << newItem.id();
+    foreach (const auto &contextUid, newContexts) {
+        Q_ASSERT(m_contexts.contains(contextUid));
+        m_contextItems[contextUid] << newItem.id();
     }
 
-    m_monitor->changeItem(reconstructItemDependencies(newItem));
+    if (isContext(item)) {
+        modifyContext(item);
+    } else {
+        m_monitor->changeItem(reconstructItemDependencies(newItem));
+    }
 }
 
 void AkonadiFakeData::removeItem(const Akonadi::Item &item)
 {
+    Q_ASSERT(item.isValid());
     Q_ASSERT(m_items.contains(item.id()));
     const auto parentId = findParentId(m_items[item.id()]);
     const auto i = m_items.take(item.id());
     m_childItems[parentId].removeAll(item.id());
 
-    foreach (const Akonadi::Tag &tag, item.tags()) {
-        m_tagItems[tag.id()].removeAll(item.id());
+    foreach (const auto &contextUid, extractContextUids(item)) {
+        m_contextItems[contextUid].removeAll(item.id());
     }
 
-    m_monitor->removeItem(reconstructItemDependencies(i));
+    if (isContext(item)) {
+        removeContext(item);
+    } else {
+        m_monitor->removeItem(reconstructItemDependencies(i));
+    }
 }
 
 Akonadi::MonitorInterface *AkonadiFakeData::createMonitor()
@@ -338,12 +403,6 @@
                      monitor, &AkonadiFakeMonitor::changeCollectionSelection);
     QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::collectionRemoved,
                      monitor, &AkonadiFakeMonitor::removeCollection);
-    QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::tagAdded,
-                     monitor, &AkonadiFakeMonitor::addTag);
-    QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::tagChanged,
-                     monitor, &AkonadiFakeMonitor::changeTag);
-    QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::tagRemoved,
-                     monitor, &AkonadiFakeMonitor::removeTag);
     QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::itemAdded,
                      monitor, &AkonadiFakeMonitor::addItem);
     QObject::connect(m_monitor.data(), &AkonadiFakeMonitor::itemChanged,
@@ -386,16 +445,6 @@
     return it.key();
 }
 
-Akonadi::Tag::Id AkonadiFakeData::maxTagId() const
-{
-    if (m_tags.isEmpty())
-        return 0;
-
-    auto it = std::max_element(m_tags.constBegin(), m_tags.constEnd(),
-                               idLessThan<Akonadi::Tag>);
-    return it.key();
-}
-
 Akonadi::Collection AkonadiFakeData::reconstructAncestors(const Akonadi::Collection &collection,
                                                           const Akonadi::Collection &root) const
 {
@@ -417,15 +466,6 @@
 {
     auto result = item;
     result.setParentCollection(reconstructAncestors(item.parentCollection(), root));
-
-    auto tags = item.tags();
-    std::transform(tags.constBegin(), tags.constEnd(),
-                   tags.begin(),
-                   [=] (const Akonadi::Tag &t) {
-                       return tag(t.id());
-                   });
-    result.setTags(tags);
-
     return result;
 }
 
diff --git a/tests/testlib/akonadifakedataxmlloader.cpp b/tests/testlib/akonadifakedataxmlloader.cpp
--- a/tests/testlib/akonadifakedataxmlloader.cpp
+++ b/tests/testlib/akonadifakedataxmlloader.cpp
@@ -41,19 +41,9 @@
     Akonadi::XmlDocument doc(fileName);
     Q_ASSERT(doc.isValid());
 
-    Akonadi::Tag::Id tagId = m_data->maxTagId() + 1;
     Akonadi::Collection::Id collectionId = m_data->maxCollectionId() + 1;
     Akonadi::Item::Id itemId = m_data->maxItemId() + 1;
 
-    QHash<QString, Akonadi::Tag> tagByRid;
-
-    foreach (const Akonadi::Tag &tag, doc.tags()) {
-        auto t = tag;
-        t.setId(tagId++);
-        m_data->createTag(t);
-        tagByRid[t.remoteId()] = t;
-    }
-
     QHash<QString, Akonadi::Collection> collectionByRid;
 
     foreach (const Akonadi::Collection &c, doc.collections()) {
@@ -90,13 +80,6 @@
             i.setId(itemId++);
             i.setParentCollection(c);
             i.setModificationTime(QDateTime::currentDateTime());
-            auto tags = i.tags();
-            std::transform(tags.constBegin(), tags.constEnd(),
-                           tags.begin(),
-                           [&tagByRid] (const Akonadi::Tag &tag) {
-                               return tagByRid.value(tag.remoteId());
-                           });
-            i.setTags(tags);
             m_data->createItem(i);
         }
     }
diff --git a/tests/testlib/akonadifakestorage.h b/tests/testlib/akonadifakestorage.h
--- a/tests/testlib/akonadifakestorage.h
+++ b/tests/testlib/akonadifakestorage.h
@@ -50,18 +50,13 @@
 
     KJob *createTransaction() override;
 
-    KJob *createTag(Akonadi::Tag tag) override;
-    KJob *updateTag(Akonadi::Tag tag) override;
-    KJob *removeTag(Akonadi::Tag tag) override;
-
     Akonadi::CollectionFetchJobInterface *fetchCollections(Akonadi::Collection collection, FetchDepth depth) override;
     Akonadi::ItemFetchJobInterface *fetchItems(Akonadi::Collection collection) override;
     Akonadi::ItemFetchJobInterface *fetchItem(Akonadi::Item item) override;
     Akonadi::ItemFetchJobInterface *fetchTagItems(Akonadi::Tag tag) override;
     Akonadi::TagFetchJobInterface *fetchTags() override;
 
 private:
-    Akonadi::Tag::Id findId(const Akonadi::Tag &tag);
     Akonadi::Collection::Id findId(const Akonadi::Collection &collection);
     Akonadi::Item::Id findId(const Akonadi::Item &item);
     Akonadi::Collection::List collectChildren(const Akonadi::Collection &root);
diff --git a/tests/testlib/akonadifakestorage.cpp b/tests/testlib/akonadifakestorage.cpp
--- a/tests/testlib/akonadifakestorage.cpp
+++ b/tests/testlib/akonadifakestorage.cpp
@@ -286,51 +286,6 @@
     return job;
 }
 
-KJob *AkonadiFakeStorage::createTag(Akonadi::Tag tag)
-{
-    Q_ASSERT(!tag.isValid());
-
-    auto job = new FakeJob;
-    if (!m_data->tag(tag.id()).isValid()) {
-        Utils::JobHandler::install(job, [=] () mutable {
-            tag.setId(m_data->maxTagId() + 1);
-            m_data->createTag(tag);
-        });
-    } else {
-        job->setExpectedError(1, QStringLiteral("The tag already exists"));
-        Utils::JobHandler::install(job, noop);
-    }
-    return job;
-}
-
-KJob *AkonadiFakeStorage::updateTag(Akonadi::Tag tag)
-{
-    auto job = new FakeJob;
-    if (m_data->tag(tag.id()).isValid()) {
-        Utils::JobHandler::install(job, [=] {
-            m_data->modifyTag(tag);
-        });
-    } else {
-        job->setExpectedError(1, QStringLiteral("The tag doesn't exist"));
-        Utils::JobHandler::install(job, noop);
-    }
-    return job;
-}
-
-KJob *AkonadiFakeStorage::removeTag(Akonadi::Tag tag)
-{
-    auto job = new FakeJob;
-    if (m_data->tag(tag.id()).isValid()) {
-        Utils::JobHandler::install(job, [=] {
-            m_data->removeTag(tag);
-        });
-    } else {
-        job->setExpectedError(1, QStringLiteral("The tag doesn't exist"));
-        Utils::JobHandler::install(job, noop);
-    }
-    return job;
-}
-
 Akonadi::CollectionFetchJobInterface *AkonadiFakeStorage::fetchCollections(Akonadi::Collection collection,
                                                                            Akonadi::StorageInterface::FetchDepth depth)
 {
@@ -408,7 +363,7 @@
 
 Akonadi::ItemFetchJobInterface *AkonadiFakeStorage::fetchTagItems(Akonadi::Tag tag)
 {
-    auto items = m_data->tagItems(findId(tag));
+    Akonadi::Item::List items; // TODO PORT = m_data->contextItems(findId(tag));
     std::transform(items.begin(), items.end(),
                    items.begin(),
                    [this] (const Akonadi::Item &item) {
@@ -433,27 +388,13 @@
 {
     auto job = new AkonadiFakeTagFetchJob;
     const auto behavior = m_data->storageBehavior().fetchTagsBehavior();
-    if (behavior == AkonadiFakeStorageBehavior::NormalFetch)
-        job->setTags(m_data->tags());
+    //if (behavior == AkonadiFakeStorageBehavior::NormalFetch)
+    // TODO PORT    job->setTags(m_data->contexts());
     job->setExpectedError(m_data->storageBehavior().fetchTagsErrorCode());
     Utils::JobHandler::install(job, noop);
     return job;
 }
 
-Akonadi::Tag::Id AkonadiFakeStorage::findId(const Akonadi::Tag &tag)
-{
-    if (tag.isValid() || tag.gid().isEmpty())
-        return tag.id();
-
-    const auto gid = tag.gid();
-    auto tags = m_data->tags();
-    auto result = std::find_if(tags.constBegin(), tags.constEnd(),
-                               [gid] (const Akonadi::Tag &tag) {
-                                   return tag.gid() == gid;
-                               });
-    return (result != tags.constEnd()) ? result->id() : tag.id();
-}
-
 Akonadi::Collection::Id AkonadiFakeStorage::findId(const Akonadi::Collection &collection)
 {
     if (collection.isValid() || collection.remoteId().isEmpty())
diff --git a/tests/testlib/akonadistoragetestbase.h b/tests/testlib/akonadistoragetestbase.h
--- a/tests/testlib/akonadistoragetestbase.h
+++ b/tests/testlib/akonadistoragetestbase.h
@@ -57,11 +57,6 @@
     void shouldNotifyItemAdded();
     void shouldNotifyItemRemoved();
     void shouldNotifyItemChanged();
-    void shouldNotifyItemTagAdded();
-    void shouldNotifyItemTagRemoved();
-    void shouldNotifyTagAdded();
-    void shouldNotifyTagRemoved();
-    void shouldNotifyTagChanged();
     void shouldReadDefaultCollectionFromSettings();
 
     // This test must be run before shouldCreateItem because createItem
@@ -80,9 +75,6 @@
     void shouldMoveItems();
     void shouldDeleteItem();
     void shouldDeleteItems();
-    void shouldCreateTag();
-    void shouldRemoveTag();
-    void shouldUpdateTag();
     void shouldUpdateCollection();
     void shouldNotifyCollectionTimestampChanges();
     void shouldNotifyCollectionSelectionChanges();
diff --git a/tests/testlib/akonadistoragetestbase.cpp b/tests/testlib/akonadistoragetestbase.cpp
--- a/tests/testlib/akonadistoragetestbase.cpp
+++ b/tests/testlib/akonadistoragetestbase.cpp
@@ -464,186 +464,6 @@
     }
 }
 
-void AkonadiStorageTestBase::shouldNotifyItemTagAdded()
-{
-    // GIVEN
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // An existing item (if we trust the test data)...
-    Akonadi::Item item = fetchItemByRID(QStringLiteral("{1d33862f-f274-4c67-ab6c-362d56521ff5}"), calendar2());
-    QVERIFY(item.isValid());
-    item.setMimeType(QStringLiteral("application/x-vnd.akonadi.calendar.todo"));
-
-    // An existing tag (if we trust the test data)
-    Akonadi::Tag tag(5);
-
-    // WHEN
-    item.setTag(tag);
-    auto storage = createStorage();
-    auto job = storage->updateItem(item);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedItem = spy.takeFirst().at(0).value<Akonadi::Item>();
-    QCOMPARE(notifiedItem.id(), item.id());
-    QVERIFY(notifiedItem.hasPayload<KCalCore::Todo::Ptr>());
-
-    Akonadi::Tag::List notifiedTags = notifiedItem.tags();
-
-    QVERIFY(notifiedTags.contains(tag));
-    foreach (const auto &tag, notifiedTags) {
-        QVERIFY(tag.isValid());
-        QVERIFY(!tag.name().isEmpty());
-        QVERIFY(!tag.type().isEmpty());
-    }
-
-    auto parent = notifiedItem.parentCollection();
-    while (parent != Akonadi::Collection::root()) {
-        QVERIFY(parent.isValid());
-        parent = parent.parentCollection();
-    }
-}
-
-void AkonadiStorageTestBase::shouldNotifyItemTagRemoved() // aka dissociate
-{
-    // GIVEN
-    auto storage = createStorage();
-    Akonadi::Tag tag = fetchTagByGID(QStringLiteral("philosophy-tag"));
-    const QString expectedRemoteIds = {QStringLiteral("{7824df00-2fd6-47a4-8319-52659dc82006}")};
-    auto job = storage->fetchTagItems(tag);
-    AKVERIFYEXEC(job->kjob());
-
-    auto item = job->items().at(0);
-    QCOMPARE(item.remoteId(), expectedRemoteIds);
-
-    QVERIFY(item.loadedPayloadParts().contains(Akonadi::Item::FullPayload));
-    QVERIFY(!item.attributes().isEmpty());
-    QVERIFY(item.modificationTime().isValid());
-    QVERIFY(!item.flags().isEmpty());
-    QVERIFY(!item.tags().isEmpty());
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // WHEN
-    item.clearTag(tag);
-    auto jobUpdate = storage->updateItem(item);
-    AKVERIFYEXEC(jobUpdate);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedItem = spy.takeFirst().at(0).value<Akonadi::Item>();
-    QCOMPARE(notifiedItem.id(), item.id());
-    QVERIFY(!notifiedItem.tags().contains(tag));
-}
-
-void AkonadiStorageTestBase::shouldNotifyTagAdded()
-{
-    // GIVEN
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagAdded);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // A tag
-    Akonadi::Tag tag;
-    tag.setGid("gid");
-    tag.setName(QStringLiteral("name"));
-    tag.setType("type");
-
-    // WHEN
-    auto storage = createStorage();
-    auto job = storage->createTag(tag);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.gid(), tag.gid());
-    QCOMPARE(notifiedTag.name(), tag.name());
-    QCOMPARE(notifiedTag.type(), tag.type());
-}
-
-void AkonadiStorageTestBase::shouldNotifyTagRemoved()
-{
-    // GIVEN
-
-    // An existing tag (if we trust the test data) connected to an existing item tagged to it
-    auto storage = createStorage();
-    Akonadi::Tag tag = fetchTagByGID(QStringLiteral("delete-me"));
-    // NOTE : this item was linked to the delete-me tag during test time
-    const QString expectedRemoteIds = {QStringLiteral("{1d33862f-f274-4c67-ab6c-362d56521ff5}")};
-    auto job = storage->fetchTagItems(tag);
-    AKVERIFYEXEC(job->kjob());
-
-    QCOMPARE(job->items().size(), 1);
-    auto itemTagged = job->items().at(0);
-    QCOMPARE(itemTagged.remoteId(), expectedRemoteIds);
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagRemoved);
-    QSignalSpy spyItemChanged(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // WHEN
-    auto jobDelete = storage->removeTag(tag);
-    AKVERIFYEXEC(jobDelete);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-    QTRY_VERIFY(!spyItemChanged.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.id(), tag.id());
-
-    QCOMPARE(spyItemChanged.size(), 1);
-    auto notifiedItem = spyItemChanged.takeFirst().at(0).value<Akonadi::Item>();
-    QCOMPARE(notifiedItem.id(), itemTagged.id());
-}
-
-void AkonadiStorageTestBase::shouldNotifyTagChanged()
-{
-    // GIVEN
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagChanged);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // An existing tag (if we trust the test data)
-    Akonadi::Tag tag(6);
-    tag.setName(QStringLiteral("Oh it changed!"));
-
-    // WHEN
-    auto storage = createStorage();
-    auto job = storage->updateTag(tag);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.id(), tag.id());
-    QCOMPARE(notifiedTag.name(), tag.name());
-}
-
 void AkonadiStorageTestBase::shouldReadDefaultCollectionFromSettings()
 {
     // GIVEN
@@ -917,92 +737,6 @@
     QCOMPARE(notifiedItem.id(), item2.id());
 }
 
-void AkonadiStorageTestBase::shouldCreateTag()
-{
-    // GIVEN
-
-    // A storage implementation
-    auto storage = createStorage();
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagAdded);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // A tag
-    Akonadi::Tag tag;
-    QString name = QStringLiteral("Tag42");
-    const QByteArray type = QByteArray("Zanshin-Context");
-    const QByteArray gid = QByteArray(name.toLatin1());
-    tag.setName(name);
-    tag.setType(QByteArray("Zanshin-Context"));
-    tag.setGid(gid);
-
-    // WHEN
-    auto job = storage->createTag(tag);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.name(), name);
-    QCOMPARE(notifiedTag.type(), type);
-    QCOMPARE(notifiedTag.gid(), gid);
-}
-
-void AkonadiStorageTestBase::shouldRemoveTag()
-{
-
-    // GIVEN
-    auto storage = createStorage();
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagRemoved);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // An existing tag
-    Akonadi::Tag tag = fetchTagByGID(QStringLiteral("errands-context"));
-
-    // WHEN
-    auto job = storage->removeTag(tag);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.id(), tag.id());
-}
-
-void AkonadiStorageTestBase::shouldUpdateTag()
-{
-    // GIVEN
-    auto storage = createStorage();
-
-    // A spied monitor
-    auto monitor = createMonitor();
-    QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagChanged);
-    MonitorSpy monitorSpy(monitor.data());
-
-    // An existing tag
-    Akonadi::Tag tag = fetchTagByGID(QStringLiteral("change-me"));
-
-    // WHEN
-    auto job = storage->updateTag(tag);
-    AKVERIFYEXEC(job);
-    monitorSpy.waitForStableState();
-    QTRY_VERIFY(!spy.isEmpty());
-
-    // THEN
-    QCOMPARE(spy.size(), 1);
-    auto notifiedTag = spy.takeFirst().at(0).value<Akonadi::Tag>();
-    QCOMPARE(notifiedTag.id(), tag.id());
-}
-
 void AkonadiStorageTestBase::shouldUpdateCollection()
 {
     // GIVEN
diff --git a/tests/units/akonadi/akonadilivequeryintegratortest.cpp b/tests/units/akonadi/akonadilivequeryintegratortest.cpp
--- a/tests/units/akonadi/akonadilivequeryintegratortest.cpp
+++ b/tests/units/akonadi/akonadilivequeryintegratortest.cpp
@@ -176,7 +176,7 @@
 
         // Reacts to remove
         // WHEN
-        data.removeTag(Akonadi::Tag(45));
+        data.removeItem(Akonadi::Item(45));
 
         // THEN
         QCOMPARE(result->data().size(), 2);
@@ -877,26 +877,6 @@
         QCOMPARE(removedId, qint64(42));
     }
 
-    void shouldCallTagRemoveHandlers()
-    {
-        // GIVEN
-        AkonadiFakeData data;
-
-        // One tag
-        data.createItem(GenTodo().withId(42).withUid("ctx-42").withTitle(QStringLiteral("42")));
-
-        auto integrator = createIntegrator(data);
-        qint64 removedId = -1;
-        integrator->addRemoveHandler([&removedId] (const Akonadi::Tag &tag) {
-            removedId = tag.id();
-        });
-
-        // WHEN
-        data.removeTag(Akonadi::Tag(42));
-
-        // THEN
-        QCOMPARE(removedId, qint64(42));
-    }
 };
 
 ZANSHIN_TEST_MAIN(AkonadiLiveQueryIntegratorTest)
diff --git a/tests/units/testlib/akonadifakedatatest.cpp b/tests/units/testlib/akonadifakedatatest.cpp
--- a/tests/units/testlib/akonadifakedatatest.cpp
+++ b/tests/units/testlib/akonadifakedatatest.cpp
@@ -23,9 +23,12 @@
 
 #include "testlib/akonadifakedata.h"
 #include "akonadi/akonadimonitorinterface.h"
+#include "akonadi/akonadiserializer.h"
 
 #include <testlib/qtest_zanshin.h>
 
+#include <akonadiserializer.h>
+
 namespace QTest {
 
 template<typename T>
@@ -50,16 +53,6 @@
                           left, right, actual, expected, file, line);
 }
 
-// More aggressive compare to make sure we just don't get tags with ids out
-template <>
-inline bool qCompare(const Akonadi::Tag &left, const Akonadi::Tag &right,
-                     const char *actual, const char *expected,
-                     const char *file, int line)
-{
-    return zCompareHelper((left == right) && (left.name() == right.name()),
-                          left, right, actual, expected, file, line);
-}
-
 // More aggressive compare to make sure we just don't get items with ids out
 template <>
 inline bool qCompare(const Akonadi::Item &left, const Akonadi::Item &right,
@@ -80,7 +73,6 @@
         : QObject(parent)
     {
         qRegisterMetaType<Akonadi::Collection>();
-        qRegisterMetaType<Akonadi::Tag>();
         qRegisterMetaType<Akonadi::Item>();
     }
 
@@ -92,7 +84,7 @@
 
         // THEN
         QVERIFY(data.collections().isEmpty());
-        QVERIFY(data.tags().isEmpty());
+        QVERIFY(data.contexts().isEmpty());
         QVERIFY(data.items().isEmpty());
     }
 
@@ -148,7 +140,7 @@
         QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Collection>(), c2);
     }
 
-    void shouldNotLooseParentCollectionOnModifyCollection()
+    void shouldNotLoseParentCollectionOnModifyCollection()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
@@ -227,6 +219,7 @@
         auto data = Testlib::AkonadiFakeData();
         QScopedPointer<Akonadi::MonitorInterface> monitor(data.createMonitor());
         QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::collectionRemoved);
+        Akonadi::Serializer serializer;
 
         auto c1 = Akonadi::Collection(42);
         c1.setName(QStringLiteral("42"));
@@ -242,13 +235,15 @@
         c3.setParentCollection(Akonadi::Collection(43));
         data.createCollection(c3);
 
-        auto i1 = Akonadi::Item(42);
-        i1.setPayloadFromData("42");
+        auto task1 = Domain::Task::Ptr::create();
+        auto i1 = serializer.createItemFromTask(task1);
+        i1.setId(42);
         i1.setParentCollection(Akonadi::Collection(43));
         data.createItem(i1);
 
-        auto i2 = Akonadi::Item(43);
-        i2.setPayloadFromData("43");
+        auto task2 = Domain::Task::Ptr::create();
+        auto i2 = serializer.createItemFromTask(task2);
+        i2.setId(43);
         i2.setParentCollection(Akonadi::Collection(44));
         data.createItem(i2);
 
@@ -279,117 +274,139 @@
         QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Collection>(), c2);
     }
 
-    void shouldCreateTags()
+    void shouldCreateContexts()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
         QScopedPointer<Akonadi::MonitorInterface> monitor(data.createMonitor());
-        QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagAdded);
+        QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::itemAdded);
+        Akonadi::Serializer serializer;
+
+        auto context1 = Domain::Context::Ptr::create();
+        context1->setName(QStringLiteral("42"));
+        context1->setProperty("todoUid", "ctx-42");
+        auto t1 = serializer.createItemFromContext(context1);
 
-        auto t1 = Akonadi::Tag(42);
-        t1.setName(QStringLiteral("42"));
-        auto t2 = Akonadi::Tag(43);
-        t2.setName(QStringLiteral("43"));
+        auto context2 = Domain::Context::Ptr::create();
+        context2->setName(QStringLiteral("43"));
+        context2->setProperty("todoUid", "ctx-43");
+        auto t2 = serializer.createItemFromContext(context2);
 
         // WHEN
-        data.createTag(t1);
-        data.createTag(t2);
+        data.createContext(t1);
+        data.createContext(t2);
 
         // THEN
-        QCOMPARE(data.tags().size(), 2);
-        QVERIFY(data.tags().contains(t1));
-        QVERIFY(data.tags().contains(t2));
-        QCOMPARE(data.tag(t1.id()), t1);
-        QCOMPARE(data.tag(t2.id()), t2);
+        QCOMPARE(data.contexts().size(), 2);
+        QVERIFY(data.contexts().contains(t1));
+        QVERIFY(data.contexts().contains(t2));
+        QCOMPARE(data.contextItem("ctx-42"), t1);
+        QCOMPARE(data.contextItem("ctx-43"), t2);
 
         QCOMPARE(spy.size(), 2);
-        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Tag>(), t1);
-        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Tag>(), t2);
+        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Item>(), t1);
+        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Item>(), t2);
     }
 
-    void shouldModifyTags()
+    void shouldModifyContexts()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
         QScopedPointer<Akonadi::MonitorInterface> monitor(data.createMonitor());
-        QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::tagChanged);
+        QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
+        Akonadi::Serializer serializer;
 
-        auto t1 = Akonadi::Tag(42);
-        t1.setName(QStringLiteral("42"));
-        data.createTag(t1);
+        auto context1 = Domain::Context::Ptr::create();
+        context1->setName(QStringLiteral("42"));
+        context1->setProperty("todoUid", "ctx-42");
+        auto t1 = serializer.createItemFromContext(context1);
+        data.createContext(t1);
 
-        auto t2 = Akonadi::Tag(t1.id());
-        t2.setName(QStringLiteral("42-bis"));
+        auto context2 = Domain::Context::Ptr::create();
+        context2->setName(QStringLiteral("42-bis"));
+        context2->setProperty("todoUid", "ctx-42");
+        auto t2 = serializer.createItemFromContext(context2);
 
         // WHEN
-        data.modifyTag(t2);
+        data.modifyContext(t2);
 
         // THEN
-        QCOMPARE(data.tags().size(), 1);
-        QCOMPARE(data.tag(t1.id()), t2);
+        QCOMPARE(data.contexts().size(), 1);
+        QCOMPARE(data.contextItem("ctx-42"), t2);
 
         QCOMPARE(spy.size(), 1);
-        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Tag>(), t2);
+        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Item>(), t2);
     }
 
-    void shouldRemoveTags()
+    void shouldRemoveContexts()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
         QScopedPointer<Akonadi::MonitorInterface> monitor(data.createMonitor());
-        QSignalSpy tagSpy(monitor.data(), &Akonadi::MonitorInterface::tagRemoved);
+        QSignalSpy contextSpy(monitor.data(), &Akonadi::MonitorInterface::itemRemoved);
         QSignalSpy itemSpy(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
+        Akonadi::Serializer serializer;
 
         auto c1 = Akonadi::Collection(42);
         data.createCollection(c1);
 
-        auto t1 = Akonadi::Tag(42);
-        t1.setName(QStringLiteral("42"));
-        data.createTag(t1);
+        auto context1 = Domain::Context::Ptr::create();
+        context1->setName(QStringLiteral("1"));
+        context1->setProperty("todoUid", "ctx-1");
+        auto t1 = serializer.createItemFromContext(context1);
+        data.createContext(t1);
 
-        auto t2 = Akonadi::Tag(43);
-        t2.setName(QStringLiteral("43"));
-        data.createTag(t2);
+        auto context2 = Domain::Context::Ptr::create();
+        context2->setName(QStringLiteral("2"));
+        context2->setProperty("todoUid", "ctx-2");
+        auto t2 = serializer.createItemFromContext(context2);
+        data.createContext(t2);
 
-        auto i1 = Akonadi::Item(42);
-        i1.setPayloadFromData("42");
+        auto task1 = Domain::Task::Ptr::create();
+        auto i1 = serializer.createItemFromTask(task1);
         i1.setParentCollection(c1);
-        i1.setTag(Akonadi::Tag(t1.id()));
+        i1.setId(42);
+        serializer.addContextToTask(context1, i1);
         data.createItem(i1);
+        QVERIFY(serializer.isContextChild(context1, i1));
 
-        auto i2 = Akonadi::Item(43);
-        i2.setPayloadFromData("43");
+        auto task2 = Domain::Task::Ptr::create();
+        auto i2 = serializer.createItemFromTask(task2);
         i2.setParentCollection(c1);
-        i2.setTag(Akonadi::Tag(t2.id()));
+        i2.setId(43);
+        serializer.addContextToTask(context2, i2);
         data.createItem(i2);
+        QVERIFY(serializer.isContextChild(context2, i2));
 
         const auto itemSet = QSet<Akonadi::Item>() << i1 << i2;
 
         // WHEN
-        data.removeTag(t2);
+        data.removeContext(t2);
 
         // THEN
-        QCOMPARE(data.tags().size(), 1);
-        QCOMPARE(data.tags().at(0), t1);
+        QCOMPARE(data.contexts().size(), 1);
+        QCOMPARE(data.contexts().at(0), t1);
 
-        QVERIFY(!data.tag(t2.id()).isValid());
+        QVERIFY(!data.contextItem("ctx-2").isValid());
 
-        QCOMPARE(data.tagItems(t1.id()).size(), 1);
-        QCOMPARE(data.tagItems(t1.id()).at(0), i1);
-        QVERIFY(data.tagItems(t2.id()).isEmpty());
+        QCOMPARE(data.contextItems("ctx-1").size(), 1);
+        QCOMPARE(data.contextItems("ctx-1").at(0), i1);
+        QVERIFY(data.contextItems("ctx-2").isEmpty());
 
         QCOMPARE(data.items().toList().toSet(), itemSet);
 
         QVERIFY(data.item(i1.id()).isValid());
-        QVERIFY(data.item(i2.id()).isValid());
-        QVERIFY(!data.item(i2.id()).tags().contains(t2));
+        const auto item2 = data.item(i2.id());
+        QVERIFY(item2.isValid());
+        QVERIFY(!serializer.isContextChild(context2, item2));
 
-        QCOMPARE(tagSpy.size(), 1);
-        QCOMPARE(tagSpy.takeFirst().at(0).value<Akonadi::Tag>(), t2);
+        QCOMPARE(contextSpy.size(), 1);
+        QCOMPARE(contextSpy.takeFirst().at(0).value<Akonadi::Item>(), t2);
 
         QCOMPARE(itemSpy.size(), 1);
-        QCOMPARE(itemSpy.first().at(0).value<Akonadi::Item>(), i2);
-        QVERIFY(!itemSpy.first().at(0).value<Akonadi::Item>().tags().contains(t2));
+        const auto emittedItem2 = itemSpy.first().at(0).value<Akonadi::Item>();
+        QCOMPARE(emittedItem2, i2);
+        QVERIFY(!serializer.isContextChild(context2, emittedItem2));
     }
 
     void shouldCreateItems()
@@ -453,7 +470,7 @@
         QCOMPARE(moveSpy.size(), 0);
     }
 
-    void shouldNotLooseParentCollectionOnModifyItem()
+    void shouldNotLoseParentCollectionOnModifyItem()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
@@ -537,55 +554,66 @@
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
-        auto t1 = Akonadi::Tag(42);
-        t1.setName(QStringLiteral("42"));
-        data.createTag(t1);
+        Akonadi::Serializer serializer;
 
-        auto i1 = Akonadi::Item(42);
-        i1.setPayloadFromData("42");
-        i1.setTag(Akonadi::Tag(42));
+        auto context1 = Domain::Context::Ptr::create();
+        context1->setName(QStringLiteral("42"));
+        context1->setProperty("todoUid", "ctx-42");
+        auto t1 = serializer.createItemFromContext(context1);
+        data.createContext(t1);
+
+        auto task1 = Domain::Task::Ptr::create();
+        auto i1 = serializer.createItemFromTask(task1);
+        i1.setId(1);
+        serializer.addContextToTask(context1, i1);
 
         // WHEN
         data.createItem(i1);
 
         // THEN
-        QCOMPARE(data.tagItems(t1.id()).size(), 1);
-        QCOMPARE(data.tagItems(t1.id()).at(0), i1);
+        QCOMPARE(data.contextItems("ctx-42").size(), 1);
+        QCOMPARE(data.contextItems("ctx-42").at(0), i1);
     }
 
     void shouldRetagItemsOnModify()
     {
         // GIVEN
         auto data = Testlib::AkonadiFakeData();
         QScopedPointer<Akonadi::MonitorInterface> monitor(data.createMonitor());
         QSignalSpy spy(monitor.data(), &Akonadi::MonitorInterface::itemChanged);
-
-        auto t1 = Akonadi::Tag(42);
-        t1.setName(QStringLiteral("42"));
-        data.createTag(t1);
-
-        auto t2 = Akonadi::Tag(43);
-        t2.setName(QStringLiteral("43"));
-        data.createTag(t2);
-
-        auto i1 = Akonadi::Item(42);
-        i1.setPayloadFromData("42");
-        i1.setTag(Akonadi::Tag(42));
+        Akonadi::Serializer serializer;
+
+        auto context1 = Domain::Context::Ptr::create();
+        context1->setName(QStringLiteral("42"));
+        context1->setProperty("todoUid", "ctx-42");
+        auto t1 = serializer.createItemFromContext(context1);
+        data.createContext(t1);
+
+        auto context2 = Domain::Context::Ptr::create();
+        context2->setName(QStringLiteral("43"));
+        context2->setProperty("todoUid", "ctx-43");
+        auto t2 = serializer.createItemFromContext(context2);
+        data.createContext(t2);
+
+        auto task1 = Domain::Task::Ptr::create();
+        auto i1 = serializer.createItemFromTask(task1);
+        i1.setId(1);
+        serializer.addContextToTask(context1, i1);
         data.createItem(i1);
 
         // WHEN
-        i1.setPayloadFromData("42-bis");
-        i1.clearTag(Akonadi::Tag(42));
-        i1.setTag(Akonadi::Tag(43));
-        data.modifyItem(i1);
+        auto i2 = serializer.createItemFromTask(task1);
+        i2.setId(1);
+        serializer.addContextToTask(context2, i2);
+        data.modifyItem(i2);
 
         // THEN
-        QVERIFY(data.tagItems(t1.id()).isEmpty());
-        QCOMPARE(data.tagItems(t2.id()).size(), 1);
-        QCOMPARE(data.tagItems(t2.id()).at(0), i1);
+        QVERIFY(data.contextItems("ctx-42").isEmpty());
+        QCOMPARE(data.contextItems("ctx-43").size(), 1);
+        QCOMPARE(data.contextItems("ctx-43").at(0), i2);
 
         QCOMPARE(spy.size(), 1);
-        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Item>(), i1);
+        QCOMPARE(spy.takeFirst().at(0).value<Akonadi::Item>(), i2);
     }
 
     void shouldRemoveItems()
diff --git a/tests/units/testlib/akonadifakedataxmlloadertest.cpp b/tests/units/testlib/akonadifakedataxmlloadertest.cpp
--- a/tests/units/testlib/akonadifakedataxmlloadertest.cpp
+++ b/tests/units/testlib/akonadifakedataxmlloadertest.cpp
@@ -49,7 +49,7 @@
         // THEN
         QVERIFY(data.collections().size() > 1);
         QVERIFY(data.items().size() > 1);
-        QVERIFY(data.tags().size() > 1);
+        QVERIFY(data.contexts().size() > 1);
 
         // Do a bit of sanity checking, no need to do much more than that as
         // the xml loading will be extensively used in the AkonadiFakeStorageTest