SDLC for To-Do List App.

1. Requirement Analysis

Users should be able to add tasks with a title.

Users should be able to mark tasks as complete.

Users should be able to delete tasks.

Tasks should be stored locally (no backend for simplicity).

The interface should be simple and mobile-friendly.

1. Design (Wireframe Sketch)

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 |     To-Do List App     |
 -------------------------
 |  [ Add Task + Button ] |
 -------------------------
 |  [ ] Task 1            |
 |  [✓] Task 2            |
 |  [ ] Task 3            |
 -------------------------
 |   Completed: 1 Task    |
 -------------------------

1. Development (Pseudocode)

START

FUNCTION main():
    INIT empty list tasks

FUNCTION addTask(taskName):
    CREATE newTask with name = taskName, status = incomplete
    APPEND newTask to tasks

FUNCTION markTaskComplete(taskID):
    FIND task in tasks by ID
    SET task.status = complete

FUNCTION deleteTask(taskID):
    REMOVE task from tasks list

FUNCTION displayTasks():
    FOR each task in tasks:
        PRINT task.name + task.status

END

1. Testing Plan

| Test Case ID | Description                          | Expected Result                     | Status |
| ------------ | ------------------------------------ | ----------------------------------- | ------ |
| TC-1         | Add a task                           | Task appears in the task list       | Pass   |
| TC-2         | Mark a task as complete              | Task status changes to "Complete"   | Pass   |
| TC-3         | Delete a task                        | Task is removed from the list       | Pass   |
| TC-4         | Add multiple tasks                   | All tasks appear correctly          | Pass   |
| TC-5         | Mark already completed task again    | Status remains "Complete"           | Pass   |
| TC-6         | Delete a non-existing task (invalid) | Error handled gracefully (no crash) | Pass   |

✅ This covers all four SDLC stages: Requirements → Design → Development → Testing.