diff --git a/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp b/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
index 6a3eb27aa..8ed317fa4 100644
--- a/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
+++ b/src/librssguard/gui/dialogs/formmessagefiltersmanager.cpp
@@ -1,3 +1,6 @@
+#include <QDateTime>
+#include <QJSEngine>
+
 // For license of this file, see <project-root-folder>/LICENSE.md.
 
 #include "gui/dialogs/formmessagefiltersmanager.h"
@@ -12,7 +15,7 @@
 
 FormMessageFiltersManager::FormMessageFiltersManager(FeedReader* reader, const QList<ServiceRoot*>& accounts, QWidget* parent)
   : QDialog(parent), m_feedsModel(new AccountCheckModel(this)), m_rootItem(new RootItem()),
-  m_accounts(accounts), m_reader(reader) {
+  m_accounts(accounts), m_reader(reader), m_loadingFilter(false) {
   m_ui.setupUi(this);
 
   GuiUtilities::applyDialogProperties(*this, qApp->icons()->fromTheme(QSL("view-list-details")));
@@ -30,6 +33,11 @@ FormMessageFiltersManager::FormMessageFiltersManager(FeedReader* reader, const Q
           this, &FormMessageFiltersManager::loadFilter);
   connect(m_ui.m_btnAddNew, &QPushButton::clicked,
           this, &FormMessageFiltersManager::addNewFilter);
+  connect(m_ui.m_txtTitle, &QLineEdit::textChanged, this, &FormMessageFiltersManager::saveSelectedFilter);
+  connect(m_ui.m_txtScript, &QPlainTextEdit::textChanged, this, &FormMessageFiltersManager::saveSelectedFilter);
+  connect(m_ui.m_btnTest, &QPushButton::clicked, this, &FormMessageFiltersManager::testFilter);
+
+  initializeTestingMessage();
 }
 
 FormMessageFiltersManager::~FormMessageFiltersManager() {
@@ -37,11 +45,11 @@ FormMessageFiltersManager::~FormMessageFiltersManager() {
 }
 
 MessageFilter* FormMessageFiltersManager::selectedFilter() const {
-  if (m_ui.m_listFilters->selectedItems().isEmpty()) {
+  if (m_ui.m_listFilters->currentItem() == nullptr) {
     return nullptr;
   }
   else {
-    return m_ui.m_listFilters->selectedItems().at(0)->data(Qt::ItemDataRole::UserRole).value<MessageFilter*>();
+    return m_ui.m_listFilters->currentItem()->data(Qt::ItemDataRole::UserRole).value<MessageFilter*>();
   }
 }
 
@@ -60,6 +68,24 @@ void FormMessageFiltersManager::addNewFilter() {
   m_ui.m_listFilters->setCurrentRow(m_ui.m_listFilters->count() - 1);
 }
 
+void FormMessageFiltersManager::saveSelectedFilter() {
+  if (m_loadingFilter) {
+    return;
+  }
+
+  auto* fltr = selectedFilter();
+
+  if (fltr == nullptr || m_ui.m_txtTitle->text().isEmpty() || m_ui.m_txtScript->toPlainText().isEmpty()) {
+    return;
+  }
+
+  fltr->setName(m_ui.m_txtTitle->text());
+  fltr->setScript(m_ui.m_txtScript->toPlainText());
+  m_ui.m_listFilters->currentItem()->setText(fltr->name());
+
+  m_reader->updateMessageFilter(fltr);
+}
+
 void FormMessageFiltersManager::loadFilter() {
   auto* filter = selectedFilter();
   auto* acc = selectedAccount();
@@ -68,7 +94,32 @@ void FormMessageFiltersManager::loadFilter() {
   updateFeedAssignments(filter, acc);
 }
 
+void FormMessageFiltersManager::testFilter() {
+  // Perform per-message filtering.
+  QJSEngine filter_engine;
+  QSqlDatabase database = qApp->database()->connection(metaObject()->className());
+
+  // Create JavaScript communication wrapper for the message.
+  MessageObject msg_obj(&database, QString::number(NO_PARENT_CATEGORY), NO_PARENT_CATEGORY);
+
+  // Register the wrapper.
+  auto js_object = filter_engine.newQObject(&msg_obj);
+
+  filter_engine.installExtensions(QJSEngine::Extension::ConsoleExtension);
+  filter_engine.globalObject().setProperty("msg", js_object);
+
+  Message msg = testingMessage();
+
+  msg_obj.setMessage(&msg);
+
+  auto* fltr = selectedFilter();
+  FilteringAction decision = fltr->filterMessage(&filter_engine);
+  int aa = 5;
+}
+
 void FormMessageFiltersManager::showFilter(MessageFilter* filter) {
+  m_loadingFilter = true;
+
   if (filter == nullptr) {
     m_ui.m_txtTitle->clear();
     m_ui.m_txtScript->clear();
@@ -79,6 +130,33 @@ void FormMessageFiltersManager::showFilter(MessageFilter* filter) {
     m_ui.m_txtScript->setPlainText(filter->script());
     m_ui.m_gbDetails->setEnabled(true);
   }
+
+  m_loadingFilter = false;
 }
 
 void FormMessageFiltersManager::updateFeedAssignments(MessageFilter* filter, ServiceRoot* account) {}
+
+void FormMessageFiltersManager::initializeTestingMessage() {
+  m_ui.m_cbSampleImportant->setChecked(true);
+  m_ui.m_txtSampleUrl->setText(QSL("https://mynews.com/news/5"));
+  m_ui.m_txtSampleTitle->setText(QSL("Year of Linux Desktop"));
+  m_ui.m_txtSampleAuthor->setText(QSL("Napoleon Bonaparte"));
+  m_ui.m_txtSampleContents->setPlainText(QSL("<p>Browsers usually insert quotation marks around the q element.</p>"
+                                             "<p>WWF's goal is to: <q>Build a future where people live in harmony "
+                                             "with nature.</q></p>"));
+  m_ui.m_txtSampleCreatedOn->setText(QString::number(QDateTime::currentDateTimeUtc().toMSecsSinceEpoch()));
+}
+
+Message FormMessageFiltersManager::testingMessage() const {
+  Message msg;
+
+  msg.m_url = m_ui.m_txtSampleUrl->text();
+  msg.m_title = m_ui.m_txtSampleTitle->text();
+  msg.m_author = m_ui.m_txtSampleAuthor->text();
+  msg.m_isRead = m_ui.m_cbSampleRead->isChecked();
+  msg.m_isImportant = m_ui.m_cbSampleImportant->isChecked();
+  msg.m_created = QDateTime::fromMSecsSinceEpoch(m_ui.m_txtSampleCreatedOn->text().toLongLong());
+  msg.m_contents = m_ui.m_txtSampleContents->toPlainText();
+
+  return msg;
+}
diff --git a/src/librssguard/gui/dialogs/formmessagefiltersmanager.h b/src/librssguard/gui/dialogs/formmessagefiltersmanager.h
index d8c4663ef..d80cd810a 100644
--- a/src/librssguard/gui/dialogs/formmessagefiltersmanager.h
+++ b/src/librssguard/gui/dialogs/formmessagefiltersmanager.h
@@ -25,7 +25,9 @@ class FormMessageFiltersManager : public QDialog {
 
   private slots:
     void addNewFilter();
+    void saveSelectedFilter();
     void loadFilter();
+    void testFilter();
 
     // Display filter title/contents.
     void showFilter(MessageFilter* filter);
@@ -33,12 +35,17 @@ class FormMessageFiltersManager : public QDialog {
     // Load feeds/categories of the account, place checkmarks where filter is used.
     void updateFeedAssignments(MessageFilter* filter, ServiceRoot* account);
 
+  private:
+    void initializeTestingMessage();
+    Message testingMessage() const;
+
   private:
     Ui::FormMessageFiltersManager m_ui;
     AccountCheckModel* m_feedsModel;
     RootItem* m_rootItem;
     QList<ServiceRoot*> m_accounts;
     FeedReader* m_reader;
+    bool m_loadingFilter;
 };
 
 #endif // FORMMESSAGEFILTERSMANAGER_H
diff --git a/src/librssguard/gui/dialogs/formmessagefiltersmanager.ui b/src/librssguard/gui/dialogs/formmessagefiltersmanager.ui
index 2f4ec1d78..f185faf8b 100644
--- a/src/librssguard/gui/dialogs/formmessagefiltersmanager.ui
+++ b/src/librssguard/gui/dialogs/formmessagefiltersmanager.ui
@@ -7,7 +7,7 @@
     <x>0</x>
     <y>0</y>
     <width>900</width>
-    <height>625</height>
+    <height>644</height>
    </rect>
   </property>
   <property name="windowTitle">
@@ -117,6 +117,12 @@
           <property name="orientation">
            <enum>Qt::Horizontal</enum>
           </property>
+          <property name="sizeHint" stdset="0">
+           <size>
+            <width>0</width>
+            <height>0</height>
+           </size>
+          </property>
          </spacer>
         </item>
        </layout>
@@ -135,12 +141,6 @@
        <layout class="QHBoxLayout" name="horizontalLayout_3">
         <item>
          <widget class="QPlainTextEdit" name="m_txtScript">
-          <property name="sizePolicy">
-           <sizepolicy hsizetype="Expanding" vsizetype="Expanding">
-            <horstretch>0</horstretch>
-            <verstretch>1</verstretch>
-           </sizepolicy>
-          </property>
           <property name="placeholderText">
            <string>Your JavaScript-based message filtering logic</string>
           </property>
@@ -155,14 +155,14 @@
            <item row="0" column="0" colspan="2">
             <layout class="QHBoxLayout" name="horizontalLayout_4">
              <item>
-              <widget class="QCheckBox" name="checkBox">
+              <widget class="QCheckBox" name="m_cbSampleRead">
                <property name="text">
                 <string>Read</string>
                </property>
               </widget>
              </item>
              <item>
-              <widget class="QCheckBox" name="checkBox_2">
+              <widget class="QCheckBox" name="m_cbSampleImportant">
                <property name="text">
                 <string>Important</string>
                </property>
@@ -189,12 +189,12 @@
               <string>Title</string>
              </property>
              <property name="buddy">
-              <cstring>lineEdit</cstring>
+              <cstring>m_txtSampleTitle</cstring>
              </property>
             </widget>
            </item>
            <item row="1" column="1">
-            <widget class="QLineEdit" name="lineEdit"/>
+            <widget class="QLineEdit" name="m_txtSampleTitle"/>
            </item>
            <item row="2" column="0">
             <widget class="QLabel" name="label_6">
@@ -202,12 +202,12 @@
               <string>URL</string>
              </property>
              <property name="buddy">
-              <cstring>lineEdit_2</cstring>
+              <cstring>m_txtSampleUrl</cstring>
              </property>
             </widget>
            </item>
            <item row="2" column="1">
-            <widget class="QLineEdit" name="lineEdit_2"/>
+            <widget class="QLineEdit" name="m_txtSampleUrl"/>
            </item>
            <item row="3" column="0">
             <widget class="QLabel" name="label_7">
@@ -215,12 +215,12 @@
               <string>Author</string>
              </property>
              <property name="buddy">
-              <cstring>lineEdit_3</cstring>
+              <cstring>m_txtSampleAuthor</cstring>
              </property>
             </widget>
            </item>
            <item row="3" column="1">
-            <widget class="QLineEdit" name="lineEdit_3"/>
+            <widget class="QLineEdit" name="m_txtSampleAuthor"/>
            </item>
            <item row="4" column="0">
             <widget class="QLabel" name="label_8">
@@ -228,12 +228,12 @@
               <string>Created on</string>
              </property>
              <property name="buddy">
-              <cstring>lineEdit_4</cstring>
+              <cstring>m_txtSampleCreatedOn</cstring>
              </property>
             </widget>
            </item>
            <item row="4" column="1">
-            <widget class="QLineEdit" name="lineEdit_4"/>
+            <widget class="QLineEdit" name="m_txtSampleCreatedOn"/>
            </item>
            <item row="5" column="0">
             <widget class="QLabel" name="label_5">
@@ -241,12 +241,12 @@
               <string>Contents</string>
              </property>
              <property name="buddy">
-              <cstring>plainTextEdit</cstring>
+              <cstring>m_txtSampleContents</cstring>
              </property>
             </widget>
            </item>
            <item row="5" column="1">
-            <widget class="QPlainTextEdit" name="plainTextEdit"/>
+            <widget class="QPlainTextEdit" name="m_txtSampleContents"/>
            </item>
           </layout>
          </widget>
@@ -258,7 +258,7 @@
         <item>
          <widget class="QPushButton" name="m_btnTest">
           <property name="text">
-           <string>&amp;Test</string>
+           <string>&amp;Test the script</string>
           </property>
          </widget>
         </item>
@@ -338,13 +338,13 @@
   <tabstop>m_txtScript</tabstop>
   <tabstop>m_btnTest</tabstop>
   <tabstop>m_btnDetailedHelp</tabstop>
-  <tabstop>checkBox</tabstop>
-  <tabstop>checkBox_2</tabstop>
-  <tabstop>lineEdit</tabstop>
-  <tabstop>lineEdit_2</tabstop>
-  <tabstop>lineEdit_3</tabstop>
-  <tabstop>lineEdit_4</tabstop>
-  <tabstop>plainTextEdit</tabstop>
+  <tabstop>m_cbSampleRead</tabstop>
+  <tabstop>m_cbSampleImportant</tabstop>
+  <tabstop>m_txtSampleTitle</tabstop>
+  <tabstop>m_txtSampleUrl</tabstop>
+  <tabstop>m_txtSampleAuthor</tabstop>
+  <tabstop>m_txtSampleCreatedOn</tabstop>
+  <tabstop>m_txtSampleContents</tabstop>
   <tabstop>m_txtErrors</tabstop>
  </tabstops>
  <resources/>
diff --git a/src/librssguard/miscellaneous/feedreader.cpp b/src/librssguard/miscellaneous/feedreader.cpp
index 4da905c7f..aff7fcd70 100644
--- a/src/librssguard/miscellaneous/feedreader.cpp
+++ b/src/librssguard/miscellaneous/feedreader.cpp
@@ -159,9 +159,14 @@ MessageFilter* FeedReader::addMessageFilter(const QString& title, const QString&
 
   // TODO: Save into database, then return.
 
+  m_messageFilters.append(fltr);
   return fltr;
 }
 
+void FeedReader::updateMessageFilter(MessageFilter* filter) {
+  // TODO: Filter's name or script is changed, save to database.
+}
+
 void FeedReader::updateAllFeeds() {
   updateFeeds(m_feedsModel->rootItem()->getSubTreeFeeds());
 }
diff --git a/src/librssguard/miscellaneous/feedreader.h b/src/librssguard/miscellaneous/feedreader.h
index 2005efd08..4bc375a90 100644
--- a/src/librssguard/miscellaneous/feedreader.h
+++ b/src/librssguard/miscellaneous/feedreader.h
@@ -55,6 +55,7 @@ class RSSGUARD_DLLSPEC FeedReader : public QObject {
     void loadSavedMessageFilters();
     QList<MessageFilter*> messageFilters() const;
     MessageFilter* addMessageFilter(const QString& title, const QString& script);
+    void updateMessageFilter(MessageFilter* filter);
 
   public slots:
     void updateAllFeeds();