Merge pull request #33768 from kunaljani1100

* pr/33768:
  Polish "Add test coverage for DomUtils"
  Add test coverage for DomUtils

Closes gh-33768

Author: snicoll

Diff for: spring-core/src/test/java/org/springframework/util/xml/DomUtilsTests.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.util.xml;
+
+import java.io.ByteArrayInputStream;
+import java.util.List;
+
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+
+import org.junit.jupiter.api.Test;
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link DomUtils}.
+ *
+ * @author Stephane Nicoll
+ * @author Kunal Jani
+ */
+class DomUtilsTests {
+
+	private static final Element SCHOOL_ELEMENT = getDocumentElement("""
+			<?xml version="1.0"?>
+			<school>TestSchool
+				<class teacher="Happy Teacher">Test Teacher One</class>
+				<class teacher="Sad Teacher">Test Teacher Two</class>
+				<principal>Test Principal</principal>
+				<guard>Fox Test</guard>
+			</school>""");
+
+
+	@Test
+	void getChildElementsByTagNameWithSeveralMatchingTags() {
+		List<Element> childElements = DomUtils.getChildElementsByTagName(SCHOOL_ELEMENT, "class", "principal");
+		assertThat(childElements).map(Element::getNodeName).containsExactly("class", "class", "principal");
+	}
+
+	@Test
+	void getChildElementsByTagNameWhenTagDoesNotExist() {
+		assertThat(DomUtils.getChildElementsByTagName(SCHOOL_ELEMENT, "teacher")).isEmpty();
+	}
+
+	@Test
+	void getChildElementByTagNameWithMatchingTag() {
+		Element principalElement = DomUtils.getChildElementByTagName(SCHOOL_ELEMENT, "principal");
+		assertThat(principalElement).isNotNull();
+		assertThat(principalElement.getTextContent()).isEqualTo("Test Principal");
+	}
+
+	@Test
+	void getChildElementByTagNameWithNonMatchingTag() {
+		assertThat(DomUtils.getChildElementByTagName(SCHOOL_ELEMENT, "teacher")).isNull();
+	}
+
+	@Test
+	void getChildElementValueByTagName() {
+		assertThat(DomUtils.getChildElementValueByTagName(SCHOOL_ELEMENT, "guard")).isEqualTo("Fox Test");
+	}
+
+	@Test
+	void getChildElementValueByTagNameWithNonMatchingTag() {
+		assertThat(DomUtils.getChildElementValueByTagName(SCHOOL_ELEMENT, "math tutor")).isNull();
+	}
+
+	@Test
+	void getChildElements() {
+		List<Element> childElements = DomUtils.getChildElements(SCHOOL_ELEMENT);
+		assertThat(childElements).map(Element::getNodeName).containsExactly("class", "class", "principal", "guard");
+	}
+
+	@Test
+	void getTextValueWithCharacterDataNode() {
+		assertThat(DomUtils.getTextValue(SCHOOL_ELEMENT)).isEqualToIgnoringWhitespace("TestSchool");
+	}
+
+	@Test
+	void getTextValueWithCommentInXml() {
+		Element elementWithComment = getDocumentElement("""
+				<?xml version="1.0"?>
+				<state>
+					<!-- This is a comment -->
+					<person>Alice</person>
+				</state>""");
+		assertThat(DomUtils.getTextValue(elementWithComment)).isBlank();
+	}
+
+	@Test
+	void getTextValueWithEntityReference() {
+		Element elementWithEntityReference = getDocumentElement("""
+				<?xml version="1.0"?>
+				<state>
+					&amp;
+					<person>Alice</person>
+				</state>""");
+		assertThat(DomUtils.getTextValue(elementWithEntityReference)).contains("&");
+	}
+
+	@Test
+	void getTextValueWithEmptyElement() {
+		Element emptyElement = getDocumentElement("""
+				<?xml version="1.0"?>
+				<person></person>""");
+		assertThat(DomUtils.getTextValue(emptyElement)).isBlank();
+	}
+
+	@Test
+	void nodeNameEqualsWhenTrue() {
+		assertThat(DomUtils.nodeNameEquals(SCHOOL_ELEMENT, "school")).isTrue();
+	}
+
+	@Test
+	void nodeNameEqualsWhenFalse() {
+		assertThat(DomUtils.nodeNameEquals(SCHOOL_ELEMENT, "college")).isFalse();
+	}
+
+
+	private static Element getDocumentElement(String xmlContent) {
+		try {
+			DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+			DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
+			Document document = documentBuilder.parse(new ByteArrayInputStream(xmlContent.getBytes()));
+			return document.getDocumentElement();
+		}
+		catch (Exception ex) {
+			throw new IllegalStateException("Failed to parse xml content:%n%s".formatted(xmlContent), ex);
+		}
+	}
+
+}