Add unit test

Signed-off-by: Arthur Chan <arthur.chan@adalogics.com>

src/test/java/org/fusesource/jansi/AnsiRendererTest.java

@@ -24,6 +24,7 @@
 import static org.fusesource.jansi.AnsiRenderer.*;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 /**
@@ -32,7 +33,6 @@
  * @author <a href="mailto:jason@planet57.com">Jason Dillon</a>
  */
 public class AnsiRendererTest {
-
     @BeforeAll
     static void setUp() {
         Ansi.setEnabled(true);
@@ -95,7 +95,6 @@ public void testRender5() {
         assertEquals(ansi().a(INTENSITY_BOLD).a("Hello").reset().toString(), str);
     }
 
-
     @Test
     public void testRenderNothing() {
         assertEquals("foo", render("foo"));
@@ -107,9 +106,14 @@ public void testRenderInvalidMissingEnd() {
         assertEquals("@|bold foo", str);
     }
 
+    @Test
+    public void testRenderInvalidEndBeforeStart() {
+        assertThrows(IllegalArgumentException.class, () -> render("@|@"));
+    }
+
     @Test
     public void testRenderInvalidMissingText() {
         String str = render("@|bold|@");
         assertEquals("@|bold|@", str);
     }
-}
+}