BAEL-3775: Clean up unit tests for Stack (#8837)

core-java-modules/core-java/src/test/java/com/baeldung/stack/StackUnitTest.java

@@ -1,123 +1,153 @@
 package com.baeldung.stack;
 
-import static org.hamcrest.CoreMatchers.equalTo;
+import org.junit.Test;
-import static org.junit.Assert.*;
 
 import java.util.Arrays;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Stack;
+import java.util.stream.Collectors;
 
-import org.junit.Test;
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 public class StackUnitTest {
 
     @Test
-    public void whenStackIsCreated_thenItHasSize0() {
+    public void whenStackIsCreated_thenItHasSizeZero() {
-        Stack intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
+
         assertEquals(0, intStack.size());
     }
 
     @Test
-    public void givenEmptyStack_whenElementIsPushed_thenStackSizeisIncreased() {
+    public void whenElementIsPushed_thenStackSizeIsIncreased() {
-        Stack intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(1);
+
         assertEquals(1, intStack.size());
     }
 
     @Test
-    public void givenEmptyStack_whenMultipleElementsArePushed_thenStackSizeisIncreased() {
+    public void whenMultipleElementsArePushed_thenStackSizeIsIncreased() {
-        Stack intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         List<Integer> intList = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
+
         boolean result = intStack.addAll(intList);
+
         assertTrue(result);
         assertEquals(7, intList.size());
     }
 
     @Test
     public void whenElementIsPoppedFromStack_thenElementIsRemovedAndSizeChanges() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
-        intStack.pop();
+
+        Integer element = intStack.pop();
+
+        assertEquals(Integer.valueOf(5), element);
         assertTrue(intStack.isEmpty());
     }
 
     @Test
     public void whenElementIsPeeked_thenElementIsNotRemovedAndSizeDoesNotChange() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
-        intStack.peek();
+
+        Integer element = intStack.peek();
+
+        assertEquals(Integer.valueOf(5), element);
         assertEquals(1, intStack.search(5));
         assertEquals(1, intStack.size());
     }
 
     @Test
     public void whenElementIsOnStack_thenSearchReturnsItsDistanceFromTheTop() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
-        assertEquals(1, intStack.search(5));
+        intStack.push(8);
+
+        assertEquals(2, intStack.search(5));
     }
 
     @Test
     public void whenElementIsOnStack_thenIndexOfReturnsItsIndex() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
+
         int indexOf = intStack.indexOf(5);
+
         assertEquals(0, indexOf);
     }
 
     @Test
     public void whenMultipleElementsAreOnStack_thenIndexOfReturnsLastElementIndex() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
         intStack.push(5);
         intStack.push(5);
+
         int lastIndexOf = intStack.lastIndexOf(5);
+
         assertEquals(2, lastIndexOf);
     }
 
     @Test
-    public void givenElementOnStack_whenRemoveElementIsInvoked_thenElementIsRemoved() {
+    public void whenRemoveElementIsInvoked_thenElementIsRemoved() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
         intStack.push(5);
+
         intStack.removeElement(5);
+
         assertEquals(1, intStack.size());
     }
 
     @Test
-    public void givenElementOnStack_whenRemoveElementAtIsInvoked_thenElementIsRemoved() {
+    public void whenRemoveElementAtIsInvoked_thenElementIsRemoved() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
         intStack.push(7);
+
         intStack.removeElementAt(1);
+
         assertEquals(-1, intStack.search(7));
     }
 
     @Test
-    public void givenElementsOnStack_whenRemoveAllElementsIsInvoked_thenAllElementsAreRemoved() {
+    public void whenRemoveAllElementsIsInvoked_thenAllElementsAreRemoved() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         intStack.push(5);
         intStack.push(7);
+
         intStack.removeAllElements();
+
         assertTrue(intStack.isEmpty());
     }
 
     @Test
     public void givenElementsOnStack_whenRemoveAllIsInvoked_thenAllElementsFromCollectionAreRemoved() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         List<Integer> intList = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
         intStack.addAll(intList);
         intStack.add(500);
+
         intStack.removeAll(intList);
+
         assertEquals(1, intStack.size());
+        assertEquals(1, intStack.search(500));
     }
 
     @Test
-    public void givenElementsOnStack_whenRemoveIfIsInvoked_thenAllElementsSatysfyingConditionAreRemoved() {
+    public void whenRemoveIfIsInvoked_thenAllElementsSatysfyingConditionAreRemoved() {
-        Stack<Integer> intStack = new Stack();
+        Stack<Integer> intStack = new Stack<>();
         List<Integer> intList = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
         intStack.addAll(intList);
+
         intStack.removeIf(element -> element < 6);
+
         assertEquals(2, intStack.size());
     }
 
@@ -126,12 +156,28 @@ public class StackUnitTest {
         Stack<Integer> intStack = new Stack<>();
         List<Integer> intList = Arrays.asList(1, 2, 3, 4, 5, 6, 7);
         intStack.addAll(intList);
+
         ListIterator<Integer> it = intStack.listIterator();
-        Stack<Integer> result = new Stack();
+
+        Stack<Integer> result = new Stack<>();
         while(it.hasNext()) {
             result.push(it.next());
         }
 
         assertThat(result, equalTo(intStack));
     }
+
+    @Test
+    public void whenStackIsFiltered_allElementsNotSatisfyingFilterConditionAreDiscarded() {
+        Stack<Integer> intStack = new Stack<>();
+        List<Integer> inputIntList = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 9, 10);
+        intStack.addAll(inputIntList);
+
+        List<Integer> filtered = intStack
+                .stream()
+                .filter(element -> element <= 3)
+                .collect(Collectors.toList());
+
+        assertEquals(3, filtered.size());
+    }
 }