Add test cases for HashSet using Open Addressing

Author: euchangxian

test/dataStructures/hashSet/openAddressing/HashSetTest.java

@@ -0,0 +1,80 @@
+package test.dataStructures.hashSet.openAddressing;
+
+import org.junit.Test;
+import src.dataStructures.hashSet.openAddressing.HashSet;
+
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.junit.Assert.*;
+
+public class HashSetTest {
+    @Test
+    public void testAdd_noDuplicates_shouldReturnTrue() {
+        HashSet<String> hashSet = new HashSet<>();
+        assertTrue(hashSet.add("Hello"));
+        assertTrue(hashSet.add("World"));
+    }
+    @Test
+    public void testAdd_withDuplicates_shouldReturnFalse() {
+        HashSet<String> hashSet = new HashSet<>();
+        assertTrue(hashSet.add("Hello"));
+        assertTrue(hashSet.add("World"));
+        assertFalse(hashSet.add("Hello")); // Adding duplicate element should return false
+    }
+
+    @Test
+    public void testContains() {
+        HashSet<String> hashSet = new HashSet<>();
+        hashSet.add("Hello");
+        hashSet.add("World");
+        assertTrue(hashSet.contains("Hello"));
+        assertTrue(hashSet.contains("World"));
+        assertFalse(hashSet.contains("Universe")); // Element not in set
+    }
+
+    @Test
+    public void testRemove() {
+        HashSet<String> hashSet = new HashSet<>();
+        hashSet.add("Hello");
+        hashSet.add("World");
+        assertTrue(hashSet.remove("Hello"));
+        assertFalse(hashSet.contains("Hello")); // Element should be removed
+        assertFalse(hashSet.remove("Universe")); // Removing non-existent element should return false
+    }
+
+    @Test
+    public void testSize() {
+        HashSet<String> hashSet = new HashSet<>();
+        assertEquals(0, hashSet.size()); // Initial size should be 0
+        hashSet.add("Hello");
+        assertEquals(1, hashSet.size()); // Size after adding one element
+        hashSet.add("World");
+        assertEquals(2, hashSet.size()); // Size after adding two elements
+        hashSet.remove("Hello");
+        assertEquals(1, hashSet.size()); // Size after removing one element
+    }
+
+    @Test
+    public void testIsEmpty() {
+        HashSet<String> hashSet = new HashSet<>();
+        assertTrue(hashSet.isEmpty()); // Initial set should be empty
+        hashSet.add("Hello");
+        assertFalse(hashSet.isEmpty()); // Set should not be empty after adding an element
+        hashSet.remove("Hello");
+        assertTrue(hashSet.isEmpty()); // Set should be empty after removing the only element
+    }
+
+    @Test
+    public void testContains_afterRemove() {
+        HashSet<Integer> hashSet = new HashSet<>();
+        Stream.iterate(0, i -> i + 1) // Populates the hashSet.
+              .limit(16)
+              .forEach(hashSet::add);
+        hashSet.remove(4);
+        assertTrue(hashSet.add(25)); // add should insert 25 at where 4 was at previously.
+        hashSet.remove(10); // Introduce a tombstone in the probe sequence for 25.
+
+        assertTrue(hashSet.contains(25)); // contains should still find 25.
+    }
+}