Fix #318 Small unit test checking that a single paragraph should crea…

…te a single page.

fixes #318

openpdf/src/test/java/org/librepdf/openpdf/independent/NumberOfPagesTest.java

@@ -0,0 +1,38 @@
+package org.librepdf.openpdf.independent;
+
+import com.lowagie.text.Document;
+import com.lowagie.text.Paragraph;
+import com.lowagie.text.pdf.PdfReader;
+import com.lowagie.text.pdf.PdfWriter;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+public class NumberOfPagesTest {
+
+    @Test
+    void whenWritingHelloWorld_thenOnlyOnePageShouldBeCreated() throws IOException {
+        // GIVEN
+        // buffer for reading the document afterwards
+        ByteArrayOutputStream outputBuffer = new ByteArrayOutputStream();
+        // step 1: create a writer that listens to the document and writes to outputBuffer
+        Document document = new Document();
+        PdfWriter writer = PdfWriter.getInstance(document, outputBuffer);
+        // step 2: open the document
+        document.open();
+        // step 3: add a paragraph to the document
+        document.add(new Paragraph("Hello World"));
+        // step 4: we close the document
+        int pagesWritten = writer.getCurrentPageNumber(); // get page "count" just before the closed
+        document.close();
+        // WHEN
+        // step 5 Read it back and count pages
+        PdfReader reader = new PdfReader(outputBuffer.toByteArray());
+        final int pagesRead = reader.getNumberOfPages();
+        // THEN
+        Assertions.assertThat(pagesWritten)
+                .isEqualTo(1)
+                .isEqualTo(pagesRead);
+    }
+}