test: add MyHashMap tests

second-part/hw-01/src/app/src/test/java/org/example/MyHashMapTest.java

@@ -0,0 +1,121 @@
+package org.example;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class MyHashMapTest {
+
+  @Test
+  void shouldPutAndGet() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    map.put("A", 10);
+
+    assertEquals(10, map.get("A"));
+  }
+
+  @Test
+  void shouldUpdateValue() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    map.put("A", 10);
+    map.put("A", 20);
+
+    assertEquals(20, map.get("A"));
+  }
+
+  @Test
+  void shouldReturnOldValueWhenUpdating() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    assertNull(map.put("A", 10));
+    assertEquals(10, map.put("A", 20));
+  }
+
+  @Test
+  void shouldReturnNullForMissingKey() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    assertNull(map.get("A"));
+  }
+
+  @Test
+  void shouldRemoveValue() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    map.put("A", 10);
+
+    assertEquals(10, map.remove("A"));
+    assertNull(map.get("A"));
+  }
+
+  @Test
+  void shouldReturnNullWhenRemovingMissingKey() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    assertNull(map.remove("A"));
+  }
+
+  @Test
+  void shouldHandleCollision() {
+    MyHashMap<Integer, String> map = new MyHashMap<>(4);
+
+    map.put(1, "A");
+    map.put(5, "B");
+
+    assertEquals("A", map.get(1));
+    assertEquals("B", map.get(5));
+  }
+
+  @Test
+  void shouldHandleRemoveWithCollision() {
+    MyHashMap<Integer, String> map = new MyHashMap<>(4);
+
+    map.put(1, "A");
+    map.put(5, "B");
+    map.put(9, "C");
+
+    assertEquals("A", map.remove(1));
+    assertEquals("B", map.get(5));
+    assertEquals("C", map.get(9));
+  }
+
+  @Test
+  void shouldResize() {
+    MyHashMap<Integer, String> map = new MyHashMap<>(2);
+
+    map.put(1, "A");
+    map.put(2, "B");
+    map.put(3, "C");
+
+    assertEquals("A", map.get(1));
+    assertEquals("B", map.get(2));
+    assertEquals("C", map.get(3));
+  }
+
+  @Test
+  void shouldReuseDeletedSlot() {
+    MyHashMap<Integer, String> map = new MyHashMap<>(4);
+
+    map.put(1, "A");
+    map.put(5, "B");
+
+    map.remove(1);
+    map.put(9, "C");
+
+    assertEquals("C", map.get(9));
+    assertEquals("B", map.get(5));
+  }
+
+  @Test
+  void shouldHandleNullKey() {
+    MyHashMap<String, Integer> map = new MyHashMap<>(4);
+
+    map.put(null, 100);
+
+    assertEquals(100, map.get(null));
+    assertEquals(100, map.remove(null));
+    assertNull(map.get(null));
+  }
+}