src/test/java/com/example/demo/service/HelloServiceTest.java

@@ -0,0 +1,55 @@
+package com.example.demo.service;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+@DisplayName("HelloService Unit Tests")
+class HelloServiceTest {
+
+    private HelloService helloService;
+
+    @BeforeEach
+    void setUp() {
+        helloService = new HelloService();
+    }
+
+    @Test
+    @DisplayName("getGreeting returns default greeting")
+    void getGreeting_ReturnsDefaultGreeting() {
+        String result = helloService.getGreeting();
+        
+        assertNotNull(result);
+        assertEquals("Hello, World!", result);
+    }
+
+    @Test
+    @DisplayName("getGreetingFor returns personalized greeting")
+    void getGreetingFor_ReturnsPersonalizedGreeting() {
+        String result = helloService.getGreetingFor("Developer");
+        
+        assertNotNull(result);
+        assertEquals("Hello, Developer!", result);
+    }
+
+    @Test
+    @DisplayName("getGreetingFor with null returns default greeting")
+    void getGreetingFor_WithNull_ReturnsDefaultGreeting() {
+        String result = helloService.getGreetingFor(null);
+        
+        assertNotNull(result);
+        assertEquals("Hello, World!", result);
+    }
+
+    @Test
+    @DisplayName("getGreetingFor with blank string returns default greeting")
+    void getGreetingFor_WithBlankString_ReturnsDefaultGreeting() {
+        String result = helloService.getGreetingFor("   ");
+        
+        assertNotNull(result);
+        assertEquals("Hello, World!", result);
+    }
+}