Merge pull request #6186 from juanvaccari/BAEL-2514

BAEL-2514 - Added unit test for Map processing

java-streams/src/test/java/com/baeldung/stream/StreamMapUnitTest.java

@@ -0,0 +1,83 @@
+package com.baeldung.stream;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Collectors;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class StreamMapUnitTest {
+
+    private Map<String, String> books;
+
+    @Before
+    public void setup() {
+        books = new HashMap<>();
+        books.put("978-0201633610", "Design patterns : elements of reusable object-oriented software");
+        books.put("978-1617291999", "Java 8 in Action: Lambdas, Streams, and functional-style programming");
+        books.put("978-0134685991", "Effective Java");
+    }
+
+
+    @Test
+    public void whenOptionalVersionCalledForExistingTitle_thenReturnOptionalWithISBN() {
+        Optional<String> optionalIsbn = books.entrySet().stream()
+                .filter(e -> "Effective Java".equals(e.getValue()))
+                .map(Map.Entry::getKey).findFirst();
+
+        assertEquals("978-0134685991", optionalIsbn.get());
+    }
+
+    @Test
+    public void whenOptionalVersionCalledForNonExistingTitle_thenReturnEmptyOptionalForISBN() {
+        Optional<String> optionalIsbn = books.entrySet().stream()
+                .filter(e -> "Non Existent Title".equals(e.getValue()))
+                .map(Map.Entry::getKey).findFirst();
+
+        assertEquals(false, optionalIsbn.isPresent());
+    }
+
+    @Test
+    public void whenMultipleResultsVersionCalledForExistingTitle_aCollectionWithMultipleValuesIsReturned() {
+        books.put("978-0321356680", "Effective Java: Second Edition");
+
+        List<String> isbnCodes = books.entrySet().stream()
+                .filter(e -> e.getValue().startsWith("Effective Java"))
+                .map(Map.Entry::getKey)
+                .collect(Collectors.toList());
+
+        assertTrue(isbnCodes.contains("978-0321356680"));
+        assertTrue(isbnCodes.contains("978-0134685991"));
+    }
+
+    @Test
+    public void whenMultipleResultsVersionCalledForNonExistingTitle_aCollectionWithNoValuesIsReturned() {
+        List<String> isbnCodes = books.entrySet().stream()
+                .filter(e -> e.getValue().startsWith("Spring"))
+                .map(Map.Entry::getKey)
+                .collect(Collectors.toList());
+
+        assertTrue(isbnCodes.isEmpty());
+    }
+
+    @Test
+    public void whenKeysFollowingPatternReturnsAllValuesForThoseKeys() {
+        List<String> titlesForKeyPattern = books.entrySet().stream()
+                .filter(e -> e.getKey().startsWith("978-0"))
+                .map(Map.Entry::getValue)
+                .collect(Collectors.toList());
+        assertEquals(2, titlesForKeyPattern.size());
+        assertTrue(titlesForKeyPattern.contains("Design patterns : elements of reusable object-oriented software"));
+        assertTrue(titlesForKeyPattern.contains("Effective Java"));
+    }
+    
+}