Add junit tests for utils classes

src/test/java/stirling/software/SPDF/utils/FileToPdfTest.java

@@ -0,0 +1,36 @@
+package stirling.software.SPDF.utils;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.io.IOException;
+
+import org.junit.jupiter.api.Test;
+
+import stirling.software.SPDF.model.api.converters.HTMLToPdfRequest;
+
+public class FileToPdfTest {
+
+    @Test
+    public void testConvertHtmlToPdf() {
+        HTMLToPdfRequest request = new HTMLToPdfRequest();
+        byte[] fileBytes = new byte[10]; // Sample file bytes
+        String fileName = "test.html"; // Sample file name
+        boolean htmlFormatsInstalled = true; // Sample boolean value
+
+        // Check if the method throws IOException
+        assertThrows(IOException.class, () -> {
+            FileToPdf.convertHtmlToPdf(request, fileBytes, fileName, htmlFormatsInstalled);
+        });
+    }
+
+    @Test
+    public void testConvertBookTypeToPdf() {
+        byte[] bytes = new byte[10]; // Sample bytes
+        String originalFilename = "test.epub"; // Sample original filename
+
+        // Check if the method throws IOException
+        assertThrows(IOException.class, () -> {
+            FileToPdf.convertBookTypeToPdf(bytes, originalFilename);
+        });
+    }
+}