Assignment #4

C#

Clone this repository and bring the code pieces you need into your BDSA Assignments GitHub repository.

Kanban Board

You are required to implement a model using Entity Framework Core for a simple kanban board for tracking work progress.

1. Install the required Microsoft.EntityFrameworkCore package.

2. Setup and configure your database host of choice.

3. Implement the following entities (POCOs) in the Entities project.

   • Task
     • Id : int
     • Title : string(100), required
     • AssignedTo : optional reference to User entity
     • Description : string(max), optional
     • State : enum (New, Active, Resolved, Closed, Removed), required
     • Tags : many-to-many reference to Tag entity
   • User
     • Id : int
     • Name : string(100), required
     • Email : string(100), required, unique
     • Tasks : list of Task entities belonging to User
   • Tag
     • Id : int
     • Name : string(50), required, unique
     • Tasks : many-to-many reference to Task entity

4. Ensure that the State property of the Task entity is stored as a string. See: https://docs.microsoft.com/en-us/ef/core/modeling/value-conversions.

5. Implement the KanbanContext required for the model above in the Entities project.

6. Implement and test the ITagRepository and/or the IUserRepository using the classes in the Entities project

7. Implement and test the ITaskRepository interface in the Core project using the TaskRepository class in the Entities project.

Business Rules

1. General

1. Trying to update or delete a non-existing entity should return NotFound.
2. Create, Read, and Update should return a proper Response.
3. Your are not allowed to write throw new ... - use the Response instead.
4. Your code must use an in-memory database for testing.
5. If a task, tag, or user is not found, return null.

2. Task Repository

1. Only tasks with the state New can be deleted from the database.
2. Deleting a task which is Active should set its state to Removed.
3. Deleting a task which is Resolved, Closed, or Removed should return Conflict.
4. Creating a task will set its state to New and Created/StateUpdated to current time in UTC.
5. Create/update task must allow for editing tags.
6. Updating the State of a task will change the StateUpdated to current time in UTC.
7. Assigning a user which does not exist should return BadRequest.
8. TaskRepository may not depend on TagRepository or UserRepository.

3. Tag Repository

1. Tags which are assigned to a task may only be deleted using the force.
2. Trying to delete a tag in use without the force should return Conflict.
3. Trying to create a tag which exists already should return Conflict.

4. User Repository

1. Users who are assigned to a task may only be deleted using the force.
2. Trying to delete a user in use without the force should return Conflict.
3. Trying to create a user which exists already (same email) should return Conflict.

Notes

Comparing actual time in a unit test can be tricky - DateTime.UtcNow is too precise - so setting a value in a test to compare with value in code will not work.

You will want to allow timing to be slightly off - maybe by 5 seconds as the following snippet demonstrates:

var expected = DateTime.UtcNow;
var actual = DateTime.UtcNow.AddSeconds(2);

Assert.Equal(expected, actual, precision: TimeSpan.FromSeconds(5)); // true

Software Engineering

Exercise 1

Study the meaning of encapsulation, inheritance, and polymorphism in OO languages. Provide a description of these concepts including UML diagram showcasing them.

Exercise 2

As a maintainance activity (i.e., after having written the code): draw a class diagram representing your implementation of the entities for the C# part. The purpose of the diagram should be to document the main relationships between the entities and their multiplicity.

Exercise 3

As a maintainance activity (i.e., after having written the code): draw a state machine diagram representing your implementation of the task entity. The purpose of the diagram should be to document the diffent states the entity can go through and the transitions that trigget the changes.

Exercise 4

For each of the SOLID principles, provide an example through either a UML diagram or a code listing that showcases the violation of the specific principle. Note: the examples do not need to be sophisticated.

Exercise 5

For each of the examples provided for SE-4, provide a refactored solution as either a UML diagram or a code listing that showcases a possible solution respecting the principle violeted. Note: the examples do not need to be sophisticated.

Note

Exercises 4 and 5 could be used in class to further discuss additional examples of the SOLID principles. If you wish to present and discuss your examples discussed in class, I would be happy to include an hour in one of the future lectures. Therefore, if the above sounds interesting, please do not hesitate to contact me. The idea would be to have a brief slot in which you would present your example of one or more of the SOLID principles.

Submitting the assignment

To submit the assignment you need to create a .pdf document using LaTeX containing the answers to the SE questions and a link to a public repository containing your fork of the completed code with the solutions to the C# part.

Members of the triplets should submit the same PDF file to pass the assignments. Make sure all group names and ID are clearly marked on the front page.