Merge pull request #25160 from midumitrescu

* pr/25160:
  Polish "Add additional tests for MultiValueMap"
  Add additional tests for MultiValueMap

Closes gh-25160

spring-core/src/test/java/org/springframework/util/CollectionUtilsTests.java

@@ -17,6 +17,7 @@
 package org.springframework.util;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -34,6 +35,8 @@
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
+ * Tests for {@link CollectionUtils}.
+ *
  * @author Rob Harrop
  * @author Juergen Hoeller
  * @author Rick Evans
@@ -211,6 +214,30 @@ void hasUniqueObject() {
 		assertThat(CollectionUtils.hasUniqueObject(list)).isFalse();
 	}
 
+	@Test
+	void conversionOfEmptyMap() {
+		MultiValueMap<String, String> asMultiValueMap = CollectionUtils.toMultiValueMap(new HashMap<>());
+		assertThat(asMultiValueMap.isEmpty()).isTrue();
+		assertThat(asMultiValueMap).isEmpty();
+	}
+
+	@Test
+	void conversionOfNonEmptyMap() {
+		Map<String, List<String>> wrapped = new HashMap<>();
+		wrapped.put("key", Arrays.asList("first", "second"));
+		MultiValueMap<String, String> asMultiValueMap = CollectionUtils.toMultiValueMap(wrapped);
+		assertThat(asMultiValueMap).containsAllEntriesOf(wrapped);
+	}
+
+	@Test
+	void changesValueByReference() {
+		Map<String, List<String>> wrapped = new HashMap<>();
+		MultiValueMap<String, String> asMultiValueMap = CollectionUtils.toMultiValueMap(wrapped);
+		assertThat(asMultiValueMap).doesNotContainKeys("key");
+		wrapped.put("key", new ArrayList<>());
+		assertThat(asMultiValueMap).containsKey("key");
+	}
+
 
 	private static final class Instance {
 

spring-core/src/test/java/org/springframework/util/MultiValueMapTests.java

@@ -0,0 +1,198 @@
+/*
+ * Copyright 2002-2023 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;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link MultiValueMap}.
+ *
+ * @author Mihai Dumitrescu
+ * @author Arjen Poutsma
+ * @author Juergen Hoeller
+ * @author Stephane Nicoll
+ */
+class MultiValueMapTests {
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void add(MultiValueMap<String, String> map) {
+		int initialSize = map.size();
+		map.add("key", "value1");
+		map.add("key", "value2");
+		assertThat(map).hasSize(initialSize + 1);
+		assertThat(map.get("key")).containsExactly("value1", "value2");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void addIfAbsentWhenAbsent(MultiValueMap<String, String> map) {
+		map.addIfAbsent("key", "value1");
+		assertThat(map.get("key")).containsExactly("value1");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void addIfAbsentWhenPresent(MultiValueMap<String, String> map) {
+		map.add("key", "value1");
+		map.addIfAbsent("key", "value2");
+		assertThat(map.get("key")).containsExactly("value1");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void set(MultiValueMap<String, String> map) {
+		map.set("key", "value1");
+		map.set("key", "value2");
+		assertThat(map.get("key")).containsExactly("value2");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void addAll(MultiValueMap<String, String> map) {
+		int initialSize = map.size();
+		map.add("key", "value1");
+		map.addAll("key", Arrays.asList("value2", "value3"));
+		assertThat(map).hasSize(initialSize + 1);
+		assertThat(map.get("key")).containsExactly("value1", "value2", "value3");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void addAllWithEmptyList(MultiValueMap<String, String> map) {
+		int initialSize = map.size();
+		map.addAll("key", Collections.emptyList());
+		assertThat(map).hasSize(initialSize + 1);
+		assertThat(map.get("key")).isEmpty();
+		assertThat(map.getFirst("key")).isNull();
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void getFirst(MultiValueMap<String, String> map) {
+		List<String> values = List.of("value1", "value2");
+		map.put("key", values);
+		assertThat(map.getFirst("key")).isEqualTo("value1");
+		assertThat(map.getFirst("other")).isNull();
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void toSingleValueMap(MultiValueMap<String, String> map) {
+		int initialSize = map.size();
+		List<String> values = List.of("value1", "value2");
+		map.put("key", values);
+		Map<String, String> singleValueMap = map.toSingleValueMap();
+		assertThat(singleValueMap).hasSize(initialSize + 1);
+		assertThat(singleValueMap.get("key")).isEqualTo("value1");
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void toSingleValueMapWithEmptyList(MultiValueMap<String, String> map) {
+		int initialSize = map.size();
+		map.put("key", Collections.emptyList());
+		Map<String, String> singleValueMap = map.toSingleValueMap();
+		assertThat(singleValueMap).hasSize(initialSize);
+		assertThat(singleValueMap.get("key")).isNull();
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void equalsOnExistingValues(MultiValueMap<String, String> map) {
+		map.clear();
+		map.set("key1", "value1");
+		assertThat(map).isEqualTo(map);
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void equalsOnEmpty(MultiValueMap<String, String> map) {
+		map.clear();
+		map.set("key1", "value1");
+		MultiValueMap<String, String> o1 = new LinkedMultiValueMap<>();
+		o1.set("key1", "value1");
+		assertThat(o1).isEqualTo(map);
+		assertThat(map).isEqualTo(o1);
+		Map<String, List<String>> o2 = new HashMap<>();
+		o2.put("key1", Collections.singletonList("value1"));
+		assertThat(o2).isEqualTo(map);
+		assertThat(map).isEqualTo(o2);
+	}
+
+	@ParameterizedTest
+	@MethodSource("objectsUnderTest")
+	void canNotChangeAnUnmodifiableMultiValueMap(MultiValueMap<String, String> map) {
+		MultiValueMap<String, String> asUnmodifiableMultiValueMap = CollectionUtils.unmodifiableMultiValueMap(map);
+		Assertions.assertAll(
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.add("key", "value")),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.addIfAbsent("key", "value")),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.addAll("key", exampleListOfValues())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.addAll(exampleMultiValueMap())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.set("key", "value")),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.setAll(exampleHashMap())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.put("key", exampleListOfValues())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.putIfAbsent("key", exampleListOfValues())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.putAll(exampleMultiValueMap())),
+				() -> Assertions.assertThrows(UnsupportedOperationException.class,
+						() -> asUnmodifiableMultiValueMap.remove("key1")));
+
+	}
+
+	private List<String> exampleListOfValues() {
+		return List.of("value1", "value2");
+	}
+
+	private Map<String, String> exampleHashMap() {
+		return Map.of("key2", "key2.value1");
+	}
+
+	private MultiValueMap<String, String> exampleMultiValueMap() {
+		LinkedMultiValueMap<String, String> map = new LinkedMultiValueMap<>();
+		map.put("key1", Arrays.asList("key1.value1", "key1.value2"));
+		return map;
+	}
+
+	static Stream<MultiValueMap<String, String>> objectsUnderTest() {
+		return Stream.of(new LinkedMultiValueMap<>(), new LinkedMultiValueMap<>(new HashMap<>()),
+				new LinkedMultiValueMap<>(new LinkedHashMap<>()),
+				new LinkedMultiValueMap<>(Map.of("existingkey", Arrays.asList("existingvalue1", "existingvalue2"))),
+				CollectionUtils.toMultiValueMap(new HashMap<>()));
+	}
+
+}