diff --git a/src/main/java/com/tagtraum/perf/gcviewer/GCViewer.java b/src/main/java/com/tagtraum/perf/gcviewer/GCViewer.java
index 50307a92..308c8106 100755
--- a/src/main/java/com/tagtraum/perf/gcviewer/GCViewer.java
+++ b/src/main/java/com/tagtraum/perf/gcviewer/GCViewer.java
@@ -26,6 +26,7 @@ public class GCViewer {
     private static final int EXIT_OK = 0;
     private static final int EXIT_EXPORT_FAILED = -1;
     private static final int EXIT_ARGS_PARSE_FAILED = -2;
+    private static final int EXIT_TOO_MANY_ARGS = -3;
     private GCViewerGuiController gcViewerGuiController;
     private GCViewerArgsParser gcViewerArgsParser;
 
@@ -39,10 +40,13 @@ public GCViewer(GCViewerGuiController gcViewerGuiController, GCViewerArgsParser
     }
 
     public static void main(final String[] args) throws InvocationTargetException, InterruptedException {
-        new GCViewer().doMain(args);
+        int exitValue = new GCViewer().doMain(args);
+        if (exitValue != 0) {
+            System.exit(exitValue);
+        }
     }
 
-    public void doMain(String[] args) throws InvocationTargetException, InterruptedException {
+    public int doMain(String[] args) throws InvocationTargetException, InterruptedException {
         GCViewerArgsParser argsParser = gcViewerArgsParser;
         try {
             argsParser.parseArguments(args);
@@ -50,11 +54,12 @@ public void doMain(String[] args) throws InvocationTargetException, InterruptedE
         catch (GCViewerArgsParserException e) {
             usage();
             LOGGER.log(Level.SEVERE, e.getMessage(), e);
-            System.exit(EXIT_ARGS_PARSE_FAILED);
+            return EXIT_ARGS_PARSE_FAILED;
         }
 
         if (argsParser.getArgumentCount() > 3) {
             usage();
+            return EXIT_TOO_MANY_ARGS;
         }
         else if (argsParser.getArgumentCount() >= 2) {
             LOGGER.info("GCViewer command line mode");
@@ -67,15 +72,16 @@ else if (argsParser.getArgumentCount() >= 2) {
             try {
                 export(gcResource, summaryFilePath, chartFilePath, type);
                 LOGGER.info("export completed successfully");
-                System.exit(EXIT_OK);
+                return EXIT_OK;
             }
             catch(Exception e) {
                 LOGGER.log(Level.SEVERE, "Error during report generation", e);
-                System.exit(EXIT_EXPORT_FAILED);
+                return EXIT_EXPORT_FAILED;
             }
         }
         else {
             gcViewerGuiController.startGui(argsParser.getArgumentCount() == 1 ? argsParser.getGcResource() : null);
+            return EXIT_OK;
         }
     }
 
diff --git a/src/test/java/com/tagtraum/perf/gcviewer/GCViewerTest.java b/src/test/java/com/tagtraum/perf/gcviewer/GCViewerTest.java
index 3209d8ea..89bf6f02 100644
--- a/src/test/java/com/tagtraum/perf/gcviewer/GCViewerTest.java
+++ b/src/test/java/com/tagtraum/perf/gcviewer/GCViewerTest.java
@@ -1,57 +1,34 @@
 package com.tagtraum.perf.gcviewer;
 
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.is;
+import static org.mockito.Matchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.verify;
+
+import java.util.Arrays;
+
 import com.tagtraum.perf.gcviewer.ctrl.impl.GCViewerGuiController;
 import com.tagtraum.perf.gcviewer.model.GCResource;
 import com.tagtraum.perf.gcviewer.model.GcResourceFile;
 import com.tagtraum.perf.gcviewer.model.GcResourceSeries;
-import org.junit.After;
-import org.junit.Before;
 import org.junit.Test;
 
-import java.io.ByteArrayOutputStream;
-import java.io.PrintStream;
-import java.util.Arrays;
-
-import static org.hamcrest.MatcherAssert.assertThat;
-import static org.hamcrest.Matchers.containsString;
-import static org.hamcrest.Matchers.isEmptyString;
-import static org.mockito.Matchers.any;
-import static org.mockito.Mockito.*;
-
 /**
  * @author martin.geldmacher
  */
 public class GCViewerTest {
 
-    private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
-    private final ByteArrayOutputStream errContent = new ByteArrayOutputStream();
-    private PrintStream oldOut;
-    private PrintStream oldErr;
-
-    @Before
-    public void replaceStreams() {
-        oldOut = System.out;
-        oldErr = System.err;
-        System.setOut(new PrintStream(outContent));
-        System.setErr(new PrintStream(errContent));
-    }
-
-    @After
-    public void revertToOriginalStreams() {
-        System.setOut(oldOut);
-        System.setErr(oldErr);
-    }
-
     @Test
     public void singleArgumentOpensGui() throws Exception {
         GCViewerGuiController controller = mock(GCViewerGuiController.class);
         GCViewer gcViewer = new GCViewer(controller, new GCViewerArgsParser());
 
         String[] args = {"some_gc.log"};
-        gcViewer.doMain(args);
+        int exitValue = gcViewer.doMain(args);
         verify(controller).startGui(new GcResourceFile("some_gc.log"));
-        assertThat(outContent.toString(), isEmptyString());
-        assertThat(errContent.toString(), isEmptyString());
+        assertThat("exitValue of doMain", exitValue, is(0));
     }
 
     @Test
@@ -60,10 +37,9 @@ public void singleArgumentWithSeriesOpensGui() throws Exception {
         GCViewer gcViewer = new GCViewer(controller, new GCViewerArgsParser());
 
         String[] args = {"some_gc.log.0;some_gc.log.1;some_gc.log.2"};
-        gcViewer.doMain(args);
+        int exitValue = gcViewer.doMain(args);
         verify(controller).startGui(new GcResourceSeries(Arrays.asList(new GcResourceFile("some_gc.log.0"), new GcResourceFile("some_gc.log.1"), new GcResourceFile("some_gc.log.2"))));
-        assertThat(outContent.toString(), isEmptyString());
-        assertThat(errContent.toString(), isEmptyString());
+        assertThat("result of doMain", exitValue, is(0));
     }
 
     @Test
@@ -72,9 +48,39 @@ public void moreThan3ArgumentsPrintsUsage() throws Exception {
         GCViewer gcViewer = new GCViewer(controller, new GCViewerArgsParser());
 
         String[] args = {"argument1", "argument2", "argument3", "argument4"};
-        gcViewer.doMain(args);
+        int exitValue = gcViewer.doMain(args);
+        verify(controller, never()).startGui(any(GCResource.class));
+        assertThat("result of doMain", exitValue, is(-3));
+    }
+
+    @Test
+    public void export() throws Exception {
+        GCViewerGuiController controller = mock(GCViewerGuiController.class);
+        GCViewer gcViewer = new GCViewer(controller, new GCViewerArgsParser());
+
+        String[] args = {"target/test-classes/openjdk/SampleSun1_7_0-01_G1_young.txt", "target/export.csv", "target/export.png", "-t", "PLAIN"};
+        int exitValue = gcViewer.doMain(args);
+        verify(controller, never()).startGui(any(GCResource.class));
+        assertThat("result of doMain", exitValue, is(0));
+    }
+
+    @Test
+    public void exportFileNotFound() throws Exception {
+        GCViewerGuiController controller = mock(GCViewerGuiController.class);
+        GCViewer gcViewer = new GCViewer(controller, new GCViewerArgsParser());
+
+        String[] args = {"doesNotExist.log", "export.csv", "-t", "PLAIN"};
+        int exitValue = gcViewer.doMain(args);
         verify(controller, never()).startGui(any(GCResource.class));
-        assertThat(outContent.toString(), containsString("Welcome to GCViewer with cmdline"));
-        assertThat(errContent.toString(), isEmptyString());
+        assertThat("result of doMain", exitValue, is(-1));
+    }
+
+    @Test
+    public void illegalExportFormat() throws Exception {
+        GCViewer gcViewer = new GCViewer();
+
+        String[] args = {"-t", "INVALID"};
+        int exitValue = gcViewer.doMain(args);
+        assertThat("result of doMain", exitValue, is(-2));
     }
 }