StringEscapeUtilsTest.testUnescapeCsvString(): Add test assertion from

apache/commons-lang#1723

Author: garydgregory

src/test/java/org/apache/commons/text/StringEscapeUtilsTest.java

@@ -431,9 +431,9 @@ void testUnescapeCsvString() {
         assertEquals("foo\uD84C\uDFB4bar", StringEscapeUtils.unescapeCsv("foo\uD84C\uDFB4bar"));
         assertEquals("", StringEscapeUtils.unescapeCsv(""));
         assertNull(StringEscapeUtils.unescapeCsv(null));
-
         assertEquals("foo.bar", StringEscapeUtils.unescapeCsv("\"foo.bar\""));
-    }
+        // a single quote is not an enclosing pair, so it passes through unchanged
+        assertEquals("\"", StringEscapeUtils.unescapeCsv("\""));    }
 
     @Test
     void testUnescapeCsvWriter() throws IOException {