Designer and creator: Aleksandr Verevkin

OOP and design patterns (NVI extension)

Both interpretation and testing suit were designed applying Object-Oriented Programing. All parts of the programs were treated as individual objects(classes) which inherit and communicate with each other.

XML interpretation using structural design pattern Facade that provide unified interface for subsystem interfaces and reduce overall complexity of the system. The Facade pattern also simplify interpret subsystem for future customization and maintenance.

In addition, for general program instance(frames, stacks and counters information) was used creational design pattern Singleton over global variables. The Singleton pattern allows single program instance to share between all other classes, which making system easier for implementing, understanding and future maintaining.

Singleton implementation:

class Program:
    __instance = None
    @staticmethod
    def get_instance():
        if Program.__instance is None:
            Program()
        return Program.__instance
    
    def __init__(self):
        Program.__instance = self

Interpret

All interpret parts were treated as different subsystems, which were unified in facade class, applying Facade design pattern architecture.

• Arguments processing

At the execution beginning, provided interpret arguments are collected and validated. For arguments collection was used python module argparse. Given input and source files were checked for existence and sufficient reading permissions.

• XML processing

After the arguments have been collected, all elements with instructions and corresponding arguments are picked, validated and sorted from the provided XML source file. To simplify searching in XML document, was used python module xml.etree.ElementTree.

• Program evaluation

When all instructions and labels are saved, program execution can start. All frames, stacks and counters are initialized in the Singleton program instance. Instructions one by one are evaluated and processed.

Testing suit

• Arguments processing

The script arguments are processed first. File paths are validated for existence and sufficient rights to read and execute. Optional parameters are set and checked for forbidden combinations. For easier arguments processing was used php function getopt.

• Test cases searching and execution

After all arguments have been saved, in the chosen or set by default directory, searching for tests is started. Depending on the --recursive parameter, subdirectories are also checked for tests. Each found test case is saved into array as TestItem object.

Array with tests is looped trough. Each saved test case is evaluated. Tests return codes and outputs are saved for future reference.

• Building html with results

Class CreateHTML is responsible for creating and saving output html/css file with test results. For each test result is created a row with all needed information from the test case for debugging possibility. Output page is made using php built-in DOM(Document Object Model) parser.