Coffee Shop Management App

A Windows Forms point-of-sale and management application for a small coffee shop —
staff take orders at the till, managers handle products and reporting from an admin panel.

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What writing tests found

The ordering logic used to live inside the form's click handlers, wired straight to MySQL. Pulling it into kafeSistemi/Siparis so it could be tested at all turned up three defects:

Two waiters could open two tabs on one table. Adding the first item read the table's state, saw it free, then opened a tab and marked it occupied. Two terminals doing that at the same moment both read free, and both opened a tab. The order screen only ever shows the newest one (ORDER BY sipID DESC LIMIT 1), so everything written to the other tab was never billed — the customer drank it and nobody found out. Claiming the table is now a single conditional statement:

UPDATE Masalar SET durum = 1 WHERE masaID = @id AND durum = 0

Exactly one request can affect a row; the loser is told so and writes to the winner's tab instead of opening a second one.

Closing a bill was two statements with no transaction. It freed the table, then wrote the total to the order row. If the second failed, the table was open for the next customer and the sale had never been recorded — with nothing left to say it happened. Both now run in one transaction.

Category headings mangled Turkish. ToUpper() on the machine's culture renders Sıcak as SıCAK on any non-Turkish Windows, and ToUpperInvariant() does it everywhere. The menu is Turkish, so the culture is now stated explicitly rather than inherited from whatever machine the till happens to run on.

32 tests. They cover the decisions — who claimed the table, what the bill adds up to, how the menu is grouped — against an in-memory fake. That the conditional UPDATE is genuinely atomic is MySQL's guarantee, not something these tests prove; they prove the code asks for it correctly.

Overview

The application is organised around three screens:

Form	Role
GirisForm	Role selection — choose the waiter till or the manager panel
Form1	Table layout — shows which tables are free and which have an open tab
SiparisForm	Order screen — the day-to-day point-of-sale interface
YoneticiForm	Manager panel — products, tables and the daily sales report

GirisForm selects a role; it does not ask for a password. That is deliberate for a till running on a machine behind the counter, but it means the manager panel is reachable by anyone with physical access to the terminal — worth knowing before deploying it anywhere the screen is not supervised.

Data access goes through a single DatabaseHelper, which reads the connection string from App.config and hands out MySQL connections to the forms. Every query is parameterised — no SQL is built by string concatenation anywhere in the project.

Data model

schema.sql creates the database, four tables and some sample rows.

Table	Purpose
Masalar	Tables in the shop; durum is 0 free / 1 occupied
Urunler	Products with price and category
Siparisler	One tab per table visit, with the running total
SiparisDetay	Line items — product, quantity and the price at the time of sale

The price is copied onto the line rather than joined from Urunler when reporting. Changing a product's price should not retroactively rewrite what yesterday's customers were charged.

Tech Stack

• C# on .NET Framework 4.7.2
• Windows Forms for the desktop UI
• MySQL via MySql.Data.MySqlClient

Project Structure

kafeSistemi/
├── GirisForm.cs        Login screen
├── SiparisForm.cs      Order / point-of-sale screen
├── YoneticiForm.cs     Manager panel
├── DatabaseHelper.cs   MySQL connection factory
├── Program.cs          Application entry point
├── packages.config     NuGet dependencies
└── Siparis/            Ordering logic, kept out of the forms so it can be tested
    ├── Adisyon.cs           A table's open bill and what it adds up to
    ├── Menu.cs              The menu, and grouping it under category headings
    ├── ISiparisDeposu.cs    What the ordering flow needs from the database
    ├── MySqlSiparisDeposu.cs  The MySQL implementation
    └── SiparisServisi.cs    Who claimed the table, and what follows from that

kafeSistemi.Tests/      xUnit, against an in-memory fake — no MySQL needed

Tests

dotnet test kafeSistemi.Tests/kafeSistemi.Tests.csproj    # 32 tests, no database required

The main project uses packages.config, which dotnet restore cannot read. If the build complains that MySql cannot be found, the packages are simply not on disk yet:

nuget restore kafeSistemi/packages.config -PackagesDirectory packages

Opening the solution in Visual Studio does this for you.

Getting Started

Requirements

• Visual Studio 2022 (or newer) with .NET Framework 4.7.2 developer pack
• A running MySQL server

Setup

1. Clone the repository and open kafeSistemi.slnx in Visual Studio.
2. Create the database and seed data:

   mysql -u root -p < schema.sql

3. Set the connection string — see below.
4. Restore NuGet packages and press F5.

Connection string

Credentials live in App.config, not in source. DatabaseHelper reads the KafeDb entry and throws a clear configuration error if it is missing, rather than failing later with a connection error that says nothing useful:

<connectionStrings>
  <add name="KafeDb"
       connectionString="server=localhost;database=bmRoastery;user=YOUR_USER;password=YOUR_PASSWORD;"
       providerName="MySql.Data.MySqlClient" />
</connectionStrings>

The value committed here is a placeholder. Keep real credentials on your own machine — App.config is tracked, so anything written into it is published.

Notes

Built to practise desktop application development in C#: multi-form navigation, data binding against a relational database, and separating the customer-facing till from the manager-only administration screen.

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_{Built by Hüseyin Kutsi Balcı}