Feat: Implemnetet CategoryDAOTest

helpmehelpapplication/src/test/java/ntnu/systemutvikling/team6/database/DAO/CategoryDAOTest.java

@@ -1,4 +1,75 @@
 package ntnu.systemutvikling.team6.database.DAO;
 
+import ntnu.systemutvikling.team6.database.DatabaseConnection;
+import org.junit.jupiter.api.*;
+import java.sql.*;
+import java.util.List;
+import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.*;
+
 public class CategoryDAOTest {
-}
+
+    // --- Mocks ---
+    private DatabaseConnection mockDbConnection;
+    private Connection         mockConn;
+    private Statement          mockStmt;
+    private ResultSet          mockRs;
+
+    private CategoryDAO categoryDAO;
+
+    @BeforeEach
+    void setUp() throws SQLException {
+        mockDbConnection = mock(DatabaseConnection.class);
+        mockConn         = mock(Connection.class);
+        mockStmt         = mock(Statement.class);
+        mockRs           = mock(ResultSet.class);
+
+        when(mockDbConnection.getMySqlConnection()).thenReturn(mockConn);
+        when(mockConn.createStatement()).thenReturn(mockStmt);
+        when(mockStmt.executeQuery(anyString())).thenReturn(mockRs);
+
+        categoryDAO = new CategoryDAO(mockDbConnection);
+    }
+
+    @Test
+    void getCategoriesFromDB_returnsAllCategories() throws SQLException {
+        when(mockRs.next()).thenReturn(true, true, true, false);
+        when(mockRs.getString("category")).thenReturn("Education", "Health", "Youth");
+
+        List<String> result = categoryDAO.getCategoriesFromDB();
+
+        assertNotNull(result);
+        assertEquals(3, result.size());
+        assertTrue(result.contains("Education"));
+        assertTrue(result.contains("Health"));
+        assertTrue(result.contains("Youth"));
+    }
+
+    @Test
+    void getCategoriesFromDB_returnsEmptyListWhenNoCategories() throws SQLException {
+        when(mockRs.next()).thenReturn(false);
+
+        List<String> result = categoryDAO.getCategoriesFromDB();
+
+        assertNotNull(result);
+        assertTrue(result.isEmpty());
+    }
+
+    @Test
+    void getCategoriesFromDB_returnsSingleCategory() throws SQLException {
+        when(mockRs.next()).thenReturn(true, false);
+        when(mockRs.getString("category")).thenReturn("Environment");
+
+        List<String> result = categoryDAO.getCategoriesFromDB();
+
+        assertEquals(1, result.size());
+        assertEquals("Environment", result.getFirst());
+    }
+
+    @Test
+    void getCategoriesFromDB_throwsRuntimeExceptionOnSQLException() throws SQLException {
+        when(mockConn.createStatement()).thenThrow(new SQLException("DB down"));
+
+        assertThrows(RuntimeException.class, () -> categoryDAO.getCategoriesFromDB());
+    }
+}