Mud River Game

Mud River is small game I made three months ago. Your goal is to splash as much mud as possible within a short time limit. It was done under a week and can be played on Github.

jUnit: Rules

Rules add special handling around tests, test cases or test suites. They can do additional validations common for all tests in the class, concurrently run multiple test instances, set up resources before each test or test case and tear them down afterwards.

The rule gets complete control over what will done with the test method, test case or test suite it is applied to. Complete control means that the rule decides what to do before and after running it and how to deal with thrown exceptions.

jUnit: Dynamic Tests Generation

Dynamic tests generation is useful when you need to run the same set of tests on many different input values or configurations. It can be achieved either using parametrized tests or using theories.

Theories are valuable when you have a bunch of data to be used as parameters and want to run tests on all their combinations. You get less control, but you do not have to write combining and iterating code by yourself. Basics about how theories work are explained on java code geeks (original at java advent calendar), so this post focus on parametrized tests.

Parametrized tests are better when you need to have good control over the input values, e.g. directory with files that are served as an input or a list of meaningful parameters combinations.

Placeholdered Maps

Placeholdered map is able to associate keys with values. User can add key value pairs into it and ask for data associated with keys. It works exactly as it would work in an ordinary map.

The additional feature is ability to use placeholders. Placeholder knows when it was created and is useful to cheat on order in which data were added into the map. If the user adds data into placeholder, the datastructure behaves as if the data were added when the placeholder was created.

We will create two such structures. First keeps key value pairs and can return last value associated with the key. Value added into placeholder is returned only if user did not added the same key after the placeholder was created. Second returns all values associated with the key in order they were put in. Placeholders can be used to add data in the middle of those lists.

Falling Ball Game

I released simple html5 game called Falling Ball. The player uses arrows to move the ball left, right and to make it jump. You get one point for every hit platform and if the ball touches screen border, any of them, then the ball dies.

Cryptography & Theory 2: What is Pseudorandom

As was concluded in the first part of this series, security without randomness is impossible. Deterministic ciphers are unable to protect against strong attackers and true random generators are impractical or hard to get, so cryptography is build on pseudorandom generators.

First two chapters of this post define what they are and explain what kind of pseudorandom generators secure cryptography needs. Third chapter introduces yet another way how to talk and think about pseudorandom generators and ciphers in general.