biojava
diff --git a/Collapse file
‎biojava-core/src/main/java/org/biojava/nbio/core/util/XMLHelper.java‎
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+11Lines changed: 11 additions & 0 deletions b/Collapse file
‎biojava-core/src/main/java/org/biojava/nbio/core/util/XMLHelper.java‎
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diff --git a/Collapse file
‎biojava-core/src/test/java/org/biojava/nbio/core/util/XMLHelperTest.java‎
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+29Lines changed: 29 additions & 0 deletions b/Collapse file
‎biojava-core/src/test/java/org/biojava/nbio/core/util/XMLHelperTest.java‎
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+29Lines changed: 29 additions & 0 deletions
@@ -158,6 +158,17 @@ public static Element selectParentElement(Element element, String parentName) {
 		return selectParentElement(parentElement, parentName);
 	}
 
+	/**
+	 * If {@code}xpathExpression{@code} is a plain string with no '/' characterr, this is 
+	 * interpreted as a child element name to search for. 
+	 * <b/>
+	 * If {@code}xpathExpression{@code} is an XPath expression, this is evaluated and is assumed
+	 * to identify a single element.
+	 * @param element
+	 * @param xpathExpression
+	 * @return A single element or null if no match or the 1st match if matches more than 1
+	 * @throws XPathExpressionException
+	 */
 	public static Element selectSingleElement(Element element, String xpathExpression) throws XPathExpressionException {
 		if (xpathExpression.indexOf("/") == -1) {
 			NodeList nodeList = element.getChildNodes();
 
@@ -14,6 +14,7 @@
 
 import javax.xml.parsers.ParserConfigurationException;
 import javax.xml.transform.TransformerException;
+import javax.xml.xpath.XPathExpressionException;
 
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
@@ -81,14 +82,42 @@ void documentToOutputStream() throws SAXException, IOException, ParserConfigurat
     @Test
     void selectParentElement() throws SAXException, IOException, ParserConfigurationException{
         Document doc = readTestDoc();
+        // get a a grandchild element
         NodeList nodes = doc.getElementsByTagName("a");
+        // can get root node
         Element el = (Element)nodes.item(0);
         Element root = XMLHelper.selectParentElement(el, "root");
         assertNotNull(root);
+        // non-existing element or if is root node returns null
         assertNull(XMLHelper.selectParentElement(el, "notexisting"));
         assertNull(XMLHelper.selectParentElement(root, "notexisting"));
 
     }
+
+    @Test
+    void selectSingleElement() throws SAXException, IOException, ParserConfigurationException, XPathExpressionException{
+        Document doc = readTestDoc();
+        Element root = (Element)doc.getElementsByTagName("root").item(0);
+
+        // not direct child
+        assertNull(XMLHelper.selectSingleElement(root, "a"));
+
+        // direct child
+        assertNotNull(XMLHelper.selectSingleElement(root, "list"));
+
+        // xpath match
+        Element found = XMLHelper.selectSingleElement(root, "/root/list/a[@id = \"2\"]");
+        assertNotNull(found);
+        assertEquals("2", found.getAttribute("id"));
+
+        // xpath no match
+        Element Notfound = XMLHelper.selectSingleElement(root, "/root/list/a[@id = \"45\"]");
+        assertNull(Notfound);
+
+        // xpath returning multiple elements returns 1st element
+        Element mult = XMLHelper.selectSingleElement(root, "/root/list/a");
+        assertNotNull(mult);
+    }
     void assertParsedDocument (Document doc){
         assertNotNull(doc);
         assertEquals(2, doc.getElementsByTagName("a").getLength());