337ab7f2c3
## About The Pull Request Refactors status effects to track their durations and tick intervals using counters. In effect, [var/duration] now directly refers to how many deciseconds are left on the status effect. I've also moved the old [var/tick_interval] [world.time] implementation to a tick-based [var/time_until_next_tick] counter. There are a couple, less noteworthy changes in here as well. The main one is that there was an unused bit of bloat code for setting tick intervals based on a random lower and upper threshold, but that can be done in tick() now so it's completely redundant, and I thus removed it entirely. That makes parts of [proc/process] much easier to read. I added/modified some unit tests (which I expect to fail) to verify that [var/duration] and [var/tick_interval] are both multiples of the subsystem wait assigned to the status effect. If the programmer wants a duration of 2.5 seconds, they expect it to work that way, but it won't because SSfastprocess only ticks once every 0.2 seconds, which 2.5 is not a multiple of. This becomes way more apparent when a status effect is set to use SSprocessing. The final, perhaps most important unit test I've added, is one that verifies that the overall tick count and overall accumulated [seconds_between_ticks] are equal to "[var/duration] / [var/tick_interval]" and "[var/duration]" respectively. ## Why It's Good For The Game The main thing this PR fixes is timing inconsistencies. Before this PR, durations and tick intervals were tracked using world.time, while the [proc/tick] call timing was dependent on the wait time of the subsystem the status effect was processing on. Thing is, SSfastprocess and SSprocessing rarely run completely in one tick during real gameplay. This led to a continuous desync where status effects were consistently inconsistent in their overall tick count. This is a big problem as [seconds_between_ticks] is constant and thus doesn't account for this difference in tick count. As an example, Changeling's Fleshmend has a duration of 10 seconds, a tick interval of 1 second and a healing rate of 4 brute per tick. Previously, if the server was lagging even slightly and it only ticked 8 times over the course of 10 seconds, you would heal 32 health rather than the 40 that a full Fleshmend would give you. The total effect potency of a status effect being reliant on server lag is incredibly stupid, especially for status effects that have an associated cost. (like the aforementioned Fleshmend) As for the refactors, they make status effect code easier to read and debug. Unit tests also make verifying things are working as intended much easier. ## Changelog 🆑 fix: Status effects now tick consistently, with Fleshmend and such giving a consistent total healing amount. Report any oddities. refactor: Status effect code is now easier to read and makes more sense. Again, report any oddities, the changes are major. /🆑
Unit Tests
What is unit testing?
Unit tests are automated code to verify that parts of the game work exactly as they should. For example, a test to make sure that the amputation surgery actually amputates the limb. These are ran every time a PR is made, and thus are very helpful for preventing bugs from cropping up in your code that would've otherwise gone unnoticed. For example, would you have thought to check that beach boys would still work the same after editing pizza? If you value your time, probably not.
On their most basic level, when UNIT_TESTS is defined, all subtypes of /datum/unit_test will have their Run proc executed. From here, if Fail is called at any point, then the tests will report as failed.
How do I write one?
- Find a relevant file.
All unit test related code is in code/modules/unit_tests. If you are adding a new test for a surgery, for example, then you'd open surgeries.dm. If a relevant file does not exist, simply create one in this folder, then #include it in _unit_tests.dm.
- Create the unit test.
To make a new unit test, you simply need to define a /datum/unit_test.
For example, let's suppose that we are creating a test to make sure a proc square correctly raises inputs to the power of two. We'd start with first:
/datum/unit_test/square/Run()
This defines our new unit test, /datum/unit_test/square. Inside this function, we're then going to run through whatever we want to check. Tests provide a few assertion functions to make this easy. For now, we're going to use TEST_ASSERT_EQUAL.
/datum/unit_test/square/Run()
TEST_ASSERT_EQUAL(square(3), 9, "square(3) did not return 9")
TEST_ASSERT_EQUAL(square(4), 16, "square(4) did not return 16")
As you can hopefully tell, we're simply checking if the output of square matches the output we are expecting. If the test fails, it'll report the error message given as well as whatever the actual output was.
- Run the unit test
Open code/_compile_options.dm and uncomment the following line.
//#define UNIT_TESTS //If this is uncommented, we do a single run though of the game setup and tear down process with unit tests in between
There are 3 ways to run unit tests
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Run tgstation.dmb in Dream Daemon. Don't bother trying to connect, you won't need to. You'll be able to see the outputs of all the tests. You'll get to see which tests failed and for what reason. If they all pass, you're set!
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Launch game from VS Code. Launch the game as normal & you will see the output of your unit tests in your fancy chat window. This is preferred as you can use the debugger to step through each line of your unit test & can use the games inbuilt debugging tools to further aid in testing
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Use VS Code Tgstation Test Explorer Extension. This allows you to run tests without launching the game & can also run focused tests(either a single or a selected group)
How to think about tests
Unit tests exist to prevent bugs that would happen in a real game. Thus, they should attempt to emulate the game world wherever possible. For example, the quick swap sanity test emulates a real scenario of the bug it fixed occurring by creating a character and giving it real items. The unrecommended alternative would be to create special test-only items. This isn't a hard rule, the reagent method exposure tests create a test-only reagent for example, but do keep it in mind.
Unit tests should also be just that--testing units of code. For example, instead of having one massive test for reagents, there are instead several smaller tests for testing exposure, metabolization, etc.
The unit testing API
You can find more information about all of these from their respective doc comments, but for a brief overview:
/datum/unit_test - The base for all tests to be ran. Subtypes must override Run(). New() and Destroy() can be used for setup and teardown. To fail, use TEST_FAIL(reason).
/datum/unit_test/proc/allocate(type, ...) - Allocates an instance of the provided type with the given arguments. Is automatically destroyed when the test is over. Commonly seen in the form of var/mob/living/carbon/human/human = allocate(/mob/living/carbon/human/consistent).
TEST_FAIL(reason) - Marks a failure at this location, but does not stop the test.
TEST_ASSERT(assertion, reason) - Stops the unit test and fails if the assertion is not met. For example: TEST_ASSERT(powered(), "Machine is not powered").
TEST_ASSERT_NOTNULL(a, message) - Same as TEST_ASSERT, but checks if !isnull(a). For example: TEST_ASSERT_NOTNULL(myatom, "My atom was never set!").
TEST_ASSERT_NULL(a, message) - Same as TEST_ASSERT, but checks if isnull(a). If not, gives a helpful message showing what a was. For example: TEST_ASSERT_NULL(delme, "Delme was never cleaned up!").
TEST_ASSERT_EQUAL(a, b, message) - Same as TEST_ASSERT, but checks if a == b. If not, gives a helpful message showing what both a and b were. For example: TEST_ASSERT_EQUAL(2 + 2, 4, "The universe is falling apart before our eyes!").
TEST_ASSERT_NOTEQUAL(a, b, message) - Same as TEST_ASSERT_EQUAL, but reversed.
TEST_FOCUS(test_path) - Only run the test provided within the parameters. Useful for reducing noise. For example, if we only want to run our example square test, we can add TEST_FOCUS(/datum/unit_test/square). Should never be pushed in a pull request--you will be laughed at.
Final Notes
- Writing tests before you attempt to fix the bug can actually speed up development a lot! It means you don't have to go in game and folllow the same exact steps manually every time. This process is known as "TDD" (test driven development). Write the test first, make sure it fails, then start work on the fix/feature, and you'll know you're done when your tests pass. If you do try this, do make sure to confirm in a non-testing environment just to double check.
- Make sure that your tests don't accidentally call RNG functions like
prob. Since RNG is seeded during tests, you may not realize you have until someone else makes a PR and the tests fail! - Do your best not to change the behavior of non-testing code during tests. While it may sometimes be necessary in the case of situations such as the above, it is still a slippery slope that can lead to the code you're testing being too different from the production environment to be useful.