diff --git a/src/demoreader.cpp b/src/demoreader.cpp
--- a/src/demoreader.cpp
+++ b/src/demoreader.cpp
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2017 Hasan Yavuz Özderya
+  Copyright © 2018 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -25,12 +25,11 @@
 #define M_PI 3.14159265358979323846
 #endif
 
-DemoReader::DemoReader(QIODevice* device, ChannelManager* channelMan,
-                       DataRecorder* recorder, QObject* parent) :
-    AbstractReader(device, channelMan, recorder, parent)
+DemoReader::DemoReader(QIODevice* device, QObject* parent) :
+    AbstractReader(device, parent)
 {
     paused = false;
-    _numOfChannels = 1;
+    _numChannels = 1;
     count = 0;
     timer.setInterval(100);
     QObject::connect(&timer, &QTimer::timeout,
@@ -51,17 +50,19 @@ void DemoReader::enable(bool enabled)
     else
     {
         timer.stop();
+        disconnectSinks();
     }
 }
 
-unsigned DemoReader::numOfChannels()
+unsigned DemoReader::numChannels() const
 {
-    return _numOfChannels;
+    return _numChannels;
 }
 
 void DemoReader::setNumOfChannels(unsigned value)
 {
-    _numOfChannels = value;
+    _numChannels = value;
+    updateNumChannels();
 }
 
 void DemoReader::pause(bool enabled)
@@ -77,13 +78,12 @@ void DemoReader::demoTimerTimeout()
 
     if (!paused)
     {
-        double* samples = new double[_numOfChannels];
-        for (unsigned ci = 0; ci < _numOfChannels; ci++)
+        SamplePack samples(1, _numChannels);
+        for (unsigned ci = 0; ci < _numChannels; ci++)
         {
             // we are calculating the fourier components of square wave
-            samples[ci] = 4*sin(2*M_PI*double((ci+1)*count)/period)/((2*(ci+1))*M_PI);
+            samples.data(ci)[0] = 4*sin(2*M_PI*double((ci+1)*count)/period)/((2*(ci+1))*M_PI);
         }
-        addData(samples, _numOfChannels);
-        delete[] samples;
+        feedOut(samples);
     }
 }
diff --git a/src/demoreader.h b/src/demoreader.h
--- a/src/demoreader.h
+++ b/src/demoreader.h
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2017 Hasan Yavuz Özderya
+  Copyright © 2018 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -38,13 +38,12 @@ class DemoReader : public AbstractReader
     Q_OBJECT
 
 public:
-    explicit DemoReader(QIODevice* device, ChannelManager* channelMan,
-                        DataRecorder* recorder, QObject* parent = 0);
+    explicit DemoReader(QIODevice* device, QObject* parent = 0);
 
     /// Demo reader is an exception so this function returns NULL
     QWidget* settingsWidget();
 
-    unsigned numOfChannels();
+    unsigned numChannels() const;
 
     void enable(bool enabled = true);
 
@@ -56,7 +55,7 @@ public slots:
 
 private:
     bool paused;
-    unsigned _numOfChannels;
+    unsigned _numChannels;
     QTimer timer;
     int count;
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -61,6 +61,7 @@ add_executable(TestReaders EXCLUDE_FROM_
   ../src/asciireadersettings.cpp
   ../src/framedreader.cpp
   ../src/framedreadersettings.cpp
+  ../src/demoreader.cpp
   ../src/commandedit.cpp
   ../src/endiannessbox.cpp
   ../src/numberformatbox.cpp
diff --git a/tests/test_readers.cpp b/tests/test_readers.cpp
--- a/tests/test_readers.cpp
+++ b/tests/test_readers.cpp
@@ -26,6 +26,7 @@
 #include "binarystreamreader.h"
 #include "asciireader.h"
 #include "framedreader.h"
+#include "demoreader.h"
 
 #include "test_helpers.h"
 
@@ -165,6 +166,52 @@ TEST_CASE("FramedReader shouldn't read w
     REQUIRE(sink.totalFed == 0);
 }
 
+TEST_CASE("DemoReader doesn't have a settings widget", "[reader, demo]")
+{
+    QBuffer bufferDev;          // not actually used
+    DemoReader reader(&bufferDev);
+
+    REQUIRE(reader.settingsWidget() == NULL);
+}
+
+TEST_CASE("Generating data with DemoReader", "[reader, demo]")
+{
+    QBuffer bufferDev;          // not actually used
+    DemoReader demoReader(&bufferDev);
+    demoReader.enable(true);
+
+    TestSink sink;
+    demoReader.connectSink(&sink);
+    REQUIRE(sink._numChannels == 1);
+
+    demoReader.setNumOfChannels(3);
+    REQUIRE(sink._numChannels == 3);
+
+    // we need to wait somehow, we are not actually looking for signals
+    QSignalSpy spy(&bufferDev, SIGNAL(readyRead()));
+    REQUIRE_FALSE(spy.wait(1000)); // we need some time for demoreader to produce data
+    REQUIRE(sink.totalFed >= 9);
+}
+
+TEST_CASE("DemoReader shouldn't generate data when paused", "[reader, demo]")
+{
+    QBuffer bufferDev;          // not actually used
+    DemoReader demoReader(&bufferDev); // paused by default
+
+    TestSink sink;
+    demoReader.connectSink(&sink);
+    REQUIRE(sink._numChannels == 1);
+
+    demoReader.setNumOfChannels(3);
+    REQUIRE(sink._numChannels == 3);
+
+    // we need to wait somehow, we are not actually looking for signals
+    QSignalSpy spy(&bufferDev, SIGNAL(readyRead()));
+    REQUIRE_FALSE(spy.wait(1000)); // we need some time for demoreader to produce data
+    REQUIRE(sink.totalFed == 0);
+}
+
+
 // Note: this is added because `QApplication` must be created for widgets
 #include <QApplication>
 int main(int argc, char* argv[])