INTECH Invoice is a simple PDF invoice generation application. This is a console program written in C# using NET 7 framework with minimal dependencies. The app is fully dockerized to be used in both development and production environments. It includes unit, integration (mostly database-related) and end-to-end tests written using NUnit testing framework.

• All monetary unit input and output values are assumed to be in euros.
• Invoice numbers have the format of yyyyMMddHHmmss where each letter corresponds to the current year, month, day, hours, minutes and seconds respectively.

• Immutability
• No static methods
• No DTOs
• No ORM
• No nulls
• No getters and setters
• No public constants
• No controllers (and MVC)
• Unit, integration and end-to-end tests

• Standard VAT rate is 20% by default. It can be changed using STANDARD_VAT_RATE environment variable.
• Time zone affects timestamps that constitute invoice numbers. It is configured as a case-insensitive string via TIME_ZONE environment variable. For example, Europe/Munich, Europe/Moscow are valid values. Local (system) time zone is used by default. More information.
• Date and money format is specified in RFC 4646 format via the CULTURE environment variable. Example: en-US, de-DE. System locale is used by default. More information