diff --git a/htmlSanityCheck-core/src/main/java/org/aim42/htmlsanitycheck/report/HtmlReporter.java b/htmlSanityCheck-core/src/main/java/org/aim42/htmlsanitycheck/report/HtmlReporter.java
index 71bd3d3e..448eb507 100644
--- a/htmlSanityCheck-core/src/main/java/org/aim42/htmlsanitycheck/report/HtmlReporter.java
+++ b/htmlSanityCheck-core/src/main/java/org/aim42/htmlsanitycheck/report/HtmlReporter.java
@@ -22,10 +22,10 @@ public class HtmlReporter extends Reporter {
     private static final Logger log = LoggerFactory.getLogger(HtmlReporter.class);
 
     private static final String REPORT_FILENAME = "index.html";
-    private String resultsOutputDir;
+    private final String resultsOutputDir;
     private FileWriter writer;
 
-    public void write(String content) {
+    protected void write(String content) {
         try {
             writer.write(content);
         } catch (IOException e) {
@@ -41,7 +41,7 @@ public HtmlReporter(PerRunResults runResults, String outputDir) {
     @Override
     public void initReport() {
         // determine a path where we can write our output file...
-        File outputFile = createOutputFile(resultsOutputDir, REPORT_FILENAME);
+        File outputFile = createOutputFile(resultsOutputDir);
 
         // init the private writer object
         try {
@@ -79,13 +79,19 @@ private void copyResourceFromJarToDirectory(String resourceName, File outputDire
         // unfortunately we currently are not able to use try-with-ressources yet.
         InputStream stream = null;
         try {
-            stream = resource.openStream();
+            if (resource != null) {
+                stream = resource.openStream();
+            } else {
+                throw new IOException("Resource not found: " + resourceName);
+            }
             Files.copy(stream, new File(outputDirectory, resourceName).toPath(), StandardCopyOption.REPLACE_EXISTING);
         } catch (final IOException e) {
             throw new UncheckedIOException(e);
         } finally {
             try {
-                stream.close();
+                if (stream != null) {
+                    stream.close();
+                }
             } catch (IOException e) {
                 throw new UncheckedIOException(e);
             }
@@ -346,13 +352,10 @@ protected void reportSingleCheckSummary(SingleCheckResults singleCheckResults) {
 
     @Override
     protected void reportSingleCheckDetails(SingleCheckResults checkResults) {
-        if (checkResults.getFindings().size() > 0) {
+        if (!checkResults.getFindings().isEmpty()) {
 
             write("\n  <ul>\n");
-            checkResults.getFindings().forEach(finding -> {
-
-                write(String.format("      <li> %s </li>\n", finding.toString()));
-            });
+            checkResults.getFindings().forEach(finding -> write(String.format("      <li> %s </li>\n", finding.toString())));
             write("  </ul>\n");
         }
     }
@@ -361,11 +364,10 @@ protected void reportSingleCheckDetails(SingleCheckResults checkResults) {
      * tries to find a writable directory. First tries dirName,
      * if that does not work takes User.dir as second choice.
      *
-     * @param dirName  : e.g. /Users/aim42/projects/htmlsc/build/report/htmlchecks
-     * @param fileName : default "index.html"
+     * @param dirName : e.g. /Users/aim42/projects/htmlsc/build/report/htmlchecks
      * @return complete path to a writable file that does not currently exist.
      */
-    private File createOutputFile(String dirName, String fileName) {
+    private File createOutputFile(String dirName) {
         File outputFolder = new File(dirName);
 
         if (!outputFolder.isDirectory() || !outputFolder.canWrite()) {
@@ -374,9 +376,7 @@ private File createOutputFile(String dirName, String fileName) {
         }
 
         // make sure we really have an existing file!
-        File outputFile = new File(outputFolder, fileName);
-
-        return outputFile;
+        return new File(outputFolder, HtmlReporter.REPORT_FILENAME);
     }
 
 
diff --git a/htmlSanityCheck-core/src/test/groovy/org/aim42/htmlsanitycheck/report/HtmlReporterTest.groovy b/htmlSanityCheck-core/src/test/groovy/org/aim42/htmlsanitycheck/report/HtmlReporterTest.groovy
new file mode 100644
index 00000000..7fca33cb
--- /dev/null
+++ b/htmlSanityCheck-core/src/test/groovy/org/aim42/htmlsanitycheck/report/HtmlReporterTest.groovy
@@ -0,0 +1,68 @@
+package org.aim42.htmlsanitycheck.report
+
+import org.aim42.htmlsanitycheck.collect.PerRunResults
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+
+import java.nio.file.Files
+
+import static org.junit.Assert.assertTrue
+import static org.junit.Assert.fail
+
+class HtmlReporterTest {
+
+    private HtmlReporter htmlReporter
+    private PerRunResults runResults
+
+    @Rule
+    public TemporaryFolder tempDir = new TemporaryFolder()
+
+    @Before
+    void setUp() {
+        runResults = new PerRunResults()
+        htmlReporter = new HtmlReporter(runResults, tempDir.getRoot().getAbsolutePath())
+    }
+
+    @Test
+    void testInitReport() {
+        htmlReporter.initReport()
+        File reportFile = new File(tempDir.getRoot(), "index.html")
+        assertTrue("Report file should be created", reportFile.exists())
+    }
+
+    @Test
+    void testWrite() {
+        htmlReporter.initReport()
+        htmlReporter.write("Test content")
+        htmlReporter.closeReport()
+        File reportFile = new File(tempDir.getRoot(), "index.html")
+        try {
+            String content = new String(Files.readAllBytes(reportFile.toPath()))
+            assertTrue("Report file should contain written content", content.contains("Test content"))
+        } catch (IOException e) {
+            fail("Failed to read report file: ${e}")
+        }
+    }
+
+    // Add more test methods for other methods in HtmlReporter
+}
+
+/*======================================================================
+
+Copyright Gernot Starke and aim42 contributors
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an
+ "AS IS" BASIS,WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+ either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+ ======================================================================*/