BAEL-6398: Java PrintStream to String (#13998)

core-java-modules/core-java-io-conversions-2/src/test/java/com/baeldung/printstreamtostring/PrintStreamToStringUtilUnitTest.java

@@ -0,0 +1,32 @@
+package com.baeldung.printstreamtostring;
+
+import static org.junit.Assert.assertNull;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.io.IOException;
+
+import org.junit.Test;
+
+public class PrintStreamToStringUtilUnitTest {
+
+    @Test
+    public void whenUsingByteArrayOutputStreamClass_thenConvert() throws IOException {
+        assertEquals("test", PrintStreamToStringUtil.usingByteArrayOutputStreamClass("test"));
+        assertEquals("", PrintStreamToStringUtil.usingByteArrayOutputStreamClass(""));
+        assertNull(PrintStreamToStringUtil.usingByteArrayOutputStreamClass(null));
+    }
+
+    @Test
+    public void whenCustomOutputStream_thenConvert() throws IOException {
+        assertEquals("world", PrintStreamToStringUtil.usingCustomOutputStream("world"));
+        assertEquals("", PrintStreamToStringUtil.usingCustomOutputStream(""));
+        assertNull(PrintStreamToStringUtil.usingCustomOutputStream(null));
+    }
+
+    @Test
+    public void whenUsingApacheCommonsIO_thenConvert() {
+        assertEquals("hello", PrintStreamToStringUtil.usingApacheCommonsIO("hello"));
+        assertEquals("", PrintStreamToStringUtil.usingApacheCommonsIO(""));
+        assertNull(PrintStreamToStringUtil.usingApacheCommonsIO(null));
+    }
+}