Added AchievementRepository tests

src/test/java/ntnu/idatt2016/v233/SmartMat/repository/user/AchievementRepositoryTest.java

+package ntnu.idatt2016.v233.SmartMat.repository.user;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+import java.util.Optional;
+
+import ntnu.idatt2016.v233.SmartMat.entity.group.Achievement;
+import ntnu.idatt2016.v233.SmartMat.repository.user.AchievementRepository;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+@ExtendWith(SpringExtension.class)
+@DataJpaTest
+class AchievementRepositoryTest {
+
+    @Autowired
+    private AchievementRepository achievementRepository;
+
+    private Achievement achievement1;
+
+    @BeforeEach
+    void setUp() {
+        achievement1 = Achievement.builder()
+                .achievementName("Eco Warrior")
+                .achievementDescription("Reduce waste by 50% in one month")
+                .build();
+
+        achievementRepository.save(achievement1);
+    }
+
+    @Test
+    void findByAchievementName() {
+        Optional<Achievement> result = achievementRepository.findByAchievementName("Eco Warrior");
+
+        assertTrue(result.isPresent());
+        assertEquals(achievement1.getAchievementName(), result.get().getAchievementName());
+        assertEquals(achievement1.getAchievementDescription(), result.get().getAchievementDescription());
+    }
+}