Refactor PatriciaTrieTest with additional test cases

Author: shimmer12

src/test/java/com/thealgorithms/datastructures/tries/PatriciaTrieTest.java

@@ -1,11 +1,18 @@
-@Test
+package com.thealgorithms.datastructures.tries;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class PatriciaTrieTest {
+
+    @Test
     void insert_splitCausesNewBranch_incrementsSize() {
         var t = new PatriciaTrie<Integer>();
-        t.put("romane", 1); // An initial key
+        t.put("romane", 1);
         assertEquals(1, t.size());
 
-        // This insertion will split the "romane" edge at "roman"
-        // and create a new branch for "us". This is where the bug occurred.
+        // Split "romane" at "roman", create branch "us"
         t.put("romanus", 2);
 
         assertEquals(2, t.size(), "Size should increment when a split creates a new key branch");
@@ -14,3 +21,56 @@ void insert_splitCausesNewBranch_incrementsSize() {
         assertEquals(1, t.get("romane"));
         assertEquals(2, t.get("romanus"));
     }
+
+    @Test
+    void basicPutGetContainsAndRemove() {
+        var t = new PatriciaTrie<String>();
+        assertTrue(t.isEmpty());
+
+        t.put("", "root");                 // empty key
+        t.put("a", "x");
+        t.put("ab", "y");
+        t.put("abc", "z");
+
+        assertEquals(4, t.size());
+        assertEquals("root", t.get(""));
+        assertEquals("x", t.get("a"));
+        assertEquals("y", t.get("ab"));
+        assertEquals("z", t.get("abc"));
+
+        assertTrue(t.contains("ab"));
+        assertFalse(t.contains("abcd"));
+
+        assertTrue(t.startsWith("ab"));
+        assertTrue(t.startsWith("abc"));
+        assertFalse(t.startsWith("zzz"));
+
+        assertTrue(t.remove("ab"));
+        assertFalse(t.contains("ab"));
+        assertEquals(3, t.size());
+
+        // removing non-existent
+        assertFalse(t.remove("ab"));
+        assertEquals(3, t.size());
+    }
+
+    @Test
+    void updatesDoNotIncreaseSize() {
+        var t = new PatriciaTrie<Integer>();
+        t.put("apple", 1);
+        t.put("apple", 2);
+        assertEquals(1, t.size());
+        assertEquals(2, t.get("apple"));
+    }
+
+    @Test
+    void nullContracts() {
+        var t = new PatriciaTrie<Integer>();
+        assertThrows(IllegalArgumentException.class, () -> t.put(null, 1));
+        assertThrows(IllegalArgumentException.class, () -> t.put("x", null));
+        assertThrows(IllegalArgumentException.class, () -> t.get(null));
+        assertThrows(IllegalArgumentException.class, () -> t.contains(null));
+        assertThrows(IllegalArgumentException.class, () -> t.remove(null));
+        assertThrows(IllegalArgumentException.class, () -> t.startsWith(null));
+    }
+}