diff --git a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialog.java b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialog.java
index 40dc19e..2971cc1 100644
--- a/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialog.java
+++ b/src/main/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialog.java
@@ -18,15 +18,17 @@ public class ClubhelperErrorDialog {
 		VerticalLayout layout = new VerticalLayout();
 		layout.addComponent(new Label(errormessage));
 		layout.addComponent(new Label(exception.getMessage()));
-		StringWriter out = new StringWriter();
-		PrintWriter writer = new PrintWriter(out);
-		exception.printStackTrace(writer);
-		layout.addComponent(toComponent(out));
+		layout.addComponent(toStacktraceComponent(exception));
 		layout.addComponent(new Button("Schließen", event -> errorDlg.close()));
 		errorDlg.setContent(layout);
 	}
 
-	public Label toComponent(StringWriter out) {
+	Label toStacktraceComponent(Exception exception) {
+
+		StringWriter out = new StringWriter();
+		PrintWriter writer = new PrintWriter(out);
+		exception.printStackTrace(writer);
+		writer.close();
 		Label label = new Label(out.toString());
 		label.setContentMode(ContentMode.PREFORMATTED);
 		return label;
diff --git a/src/test/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialogTest.java b/src/test/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialogTest.java
new file mode 100644
index 0000000..6c27b3b
--- /dev/null
+++ b/src/test/java/de/kreth/vaadin/clubhelper/vaadinclubhelper/ui/ClubhelperErrorDialogTest.java
@@ -0,0 +1,69 @@
+package de.kreth.vaadin.clubhelper.vaadinclubhelper.ui;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.verify;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import com.vaadin.ui.Component;
+import com.vaadin.ui.HasComponents;
+import com.vaadin.ui.Label;
+import com.vaadin.ui.UI;
+import com.vaadin.ui.Window;
+
+class ClubhelperErrorDialogTest {
+
+	@Mock
+	private UI ui;
+
+	@BeforeEach
+	void setUp() throws Exception {
+		MockitoAnnotations.initMocks(this);
+	}
+
+	@Test
+	void testErrorDialogContent() {
+		Exception e = new Exception("Exception message");
+		ClubhelperErrorDialog dlg = new ClubhelperErrorDialog("errormessage", e);
+		dlg.show(ui);
+		ArgumentCaptor<Window> windowCaptor = ArgumentCaptor.forClass(Window.class);
+		verify(ui).addWindow(windowCaptor.capture());
+		Window window = windowCaptor.getValue();
+		Component content = window.getContent();
+		assertTrue(content instanceof HasComponents);
+		boolean errorMessageFound = false;
+		boolean exceptionMessageFound = false;
+		boolean stacktraceFound = false;
+		StringWriter out = new StringWriter();
+		PrintWriter writer = new PrintWriter(out);
+		e.printStackTrace(writer);
+		writer.close();
+		String stacktraceLine = out.toString().split("\n")[0].trim();
+		for (Component c : (HasComponents) content) {
+			if (c instanceof Label) {
+				Label label = (Label) c;
+				String text = label.getValue();
+				if ("errormessage".equals(text)) {
+					errorMessageFound = true;
+				}
+				else if ("Exception message".equals(text)) {
+					exceptionMessageFound = true;
+				}
+				else if (text.contains(stacktraceLine)) {
+					stacktraceFound = true;
+				}
+			}
+		}
+		assertTrue(errorMessageFound, "Errormessage (caption) not found!");
+		assertTrue(exceptionMessageFound, "Exception message not found!");
+		assertTrue(stacktraceFound, "Stacktrace not found!");
+	}
+
+}