reorganize app.lua and its comments
I was so sure my comments were clear when I wrote this a year ago. They were shit. So, most probably, is the current iteration. Feedback appreciated.
This commit is contained in:
Kartik K. Agaram
parent
9c38e505a5
commit
ca4ad8a9e5
310
app.lua
310
app.lua
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@ -1,15 +1,11 @@
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-- love.run: main entrypoint function for LÖVE
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--
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-- Most apps can just use the default shown in https://love2d.org/wiki/love.run,
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-- but we need to override it to install a test harness.
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--
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-- A test harness needs to check what the 'real' code did.
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-- To do this it needs to hook into primitive operations performed by code.
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-- Our hooks all go through the `App` global. When running tests they operate
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-- on fake screen, keyboard and so on. Once all tests pass, the App global
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-- will hook into the real screen, keyboard and so on.
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--
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-- Scroll below this function for more details.
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-- but we need to override it to:
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-- * run all tests (functions starting with 'test_') on startup, and
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-- * save some state that makes it possible to switch between the main app
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-- and a source editor, while giving each the illusion of complete
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-- control.
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function love.run()
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App.snapshot_love()
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-- Tests always run at the start.
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@ -44,81 +40,14 @@ function love.run()
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end
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end
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-- I've been building LÖVE apps for a couple of months now, and often feel
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-- stupid. I seem to have a smaller short-term memory than most people, and
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-- LÖVE apps quickly grow to a point where I need longer and longer chunks of
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-- focused time to make changes to them. The reason: I don't have a way to
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-- write tests yet. So before I can change any piece of an app, I have to
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-- bring into my head all the ways it can break. This isn't the case on other
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-- platforms, where I can be productive in 5- or 10-minute increments. Because
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-- I have tests.
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-- The rest of this file wraps around various LÖVE primitives to support
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-- automated tests. Often tests will run with a fake version of a primitive
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-- that redirects to the real love.* version once we're done with tests.
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--
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-- Most test harnesses punt on testing I/O, and conventional wisdom is to test
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-- business logic, not I/O. However, any non-trivial app does non-trivial I/O
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-- that benefits from tests. And tests aren't very useful if it isn't obvious
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-- after reading them what the intent is. Including the I/O allows us to write
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-- tests that mimic how people use our program.
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--
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-- There's a major open research problem in testing I/O: how to write tests
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-- for graphics. Pixel-by-pixel assertions get too verbose, and they're often
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-- brittle because you don't care about the precise state of every last pixel.
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-- Except when you do. Pixels are usually -- but not always -- the trees
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-- rather than the forest.
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--
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-- I'm not in the business of doing research, so I'm going to shave off a
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-- small subset of the problem for myself here: how to write tests about text
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-- (ignoring font, color, etc.) on a graphic screen.
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--
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-- For example, here's how you may write a test of a simple text paginator
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-- like `less`:
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-- function test_paginator()
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-- -- initialize environment
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-- App.filesystem['/tmp/foo'] = filename([[
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-- >abc
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-- >def
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-- >ghi
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-- >jkl
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-- ]])
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-- App.args = {'/tmp/foo'}
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-- -- define a screen with room for 2 lines of text
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-- App.screen.init{
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-- width=100
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-- height=30
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-- }
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-- App.font.init{
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-- height=15
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-- }
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-- -- check that screen shows next 2 lines of text after hitting pagedown
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-- App.run_after_keychord('pagedown')
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-- App.screen.check(0, 'ghi')
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-- App.screen.check(15, 'jkl')
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-- end
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--
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-- All functions starting with 'test_' (no modules) will run before the app
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-- runs "for real". Each such test is a fake run of our entire program. It can
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-- set as much of the environment as it wants, then run the app. Here we've
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-- got a 30px screen and a 15px font, so the screen has room for 2 lines. The
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-- file we're viewing has 4 lines. We assert that hitting the 'pagedown' key
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-- shows the third and fourth lines.
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--
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-- Programs can still perform graphics, and all graphics will work in the real
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-- program. We can't yet write tests for graphics, though. Those pixels are
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-- basically always blank in tests. Really, there isn't even any
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-- representation for them. All our fake screens know about is lines of text,
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-- and what (x,y) coordinates they start at. There's some rudimentary support
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-- for concatenating all blobs of text that start at the same 'y' coordinate,
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-- but beware: text at y=100 is separate and non-overlapping with text at
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-- y=101. You have to use the test harness within these limitations for your
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-- tests to faithfully model the real world.
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--
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-- One drawback of this approach: the y coordinate used depends on font size,
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-- which feels brittle.
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--
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-- In the fullness of time App will support all side-effecting primitives
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-- exposed by LÖVE, but so far it supports just a rudimentary set of things I
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-- happen to have needed so far.
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-- Not everything is so wrapped yet. Sometimes you still have to use love.*
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-- primitives directly.
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App = {screen={}}
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App = {}
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-- save/restore various framework globals we care about -- only on very first load
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function App.snapshot_love()
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@ -144,6 +73,26 @@ function App.run_tests_and_initialize()
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App.initialize(love.arg.parseGameArguments(arg), arg)
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end
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function App.run_tests()
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local sorted_names = {}
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for name,binding in pairs(_G) do
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if name:find('test_') == 1 then
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table.insert(sorted_names, name)
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end
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end
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table.sort(sorted_names)
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for _,name in ipairs(sorted_names) do
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App.initialize_for_test()
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--? print('=== '..name)
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--? _G[name]()
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xpcall(_G[name], function(err) prepend_debug_info_to_test_failure(name, err) end)
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end
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-- clean up all test methods
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for _,name in ipairs(sorted_names) do
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_G[name] = nil
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end
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end
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function App.initialize_for_test()
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App.screen.init{width=100, height=50}
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App.screen.contents = {} -- clear screen
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@ -153,12 +102,19 @@ function App.initialize_for_test()
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App.initialize_globals()
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end
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-- App.screen.resize and App.screen.move seem like better names than
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-- love.window.setMode and love.window.setPosition respectively. They'll
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-- be side-effect-free during tests, and they'll save their results in
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-- attributes of App.screen for easy access.
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App.screen={}
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-- Use App.screen.init in tests to initialize the fake screen.
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function App.screen.init(dims)
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App.screen.width = dims.width
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App.screen.height = dims.height
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end
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-- operations on the LÖVE window within the monitor/display
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function App.screen.resize(width, height, flags)
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App.screen.width = width
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App.screen.height = height
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@ -179,6 +135,12 @@ function App.screen.position()
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return App.screen.x, App.screen.y, App.screen.displayindex
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end
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-- If you use App.screen.print instead of love.graphics.print,
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-- tests will be able to check what was printed using App.screen.check below.
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--
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-- One drawback of this approach: the y coordinate used depends on font size,
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-- which feels brittle.
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function App.screen.print(msg, x,y)
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local screen_row = 'y'..tostring(y)
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--? print('drawing "'..msg..'" at y '..tostring(y))
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@ -194,13 +156,22 @@ function App.screen.print(msg, x,y)
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end
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end
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function App.color(color)
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love.graphics.setColor(color.r, color.g, color.b, color.a)
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function App.screen.check(y, expected_contents, msg)
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--? print('checking for "'..expected_contents..'" at y '..tostring(y))
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local screen_row = 'y'..tostring(y)
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local contents = ''
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if App.screen.contents[screen_row] == nil then
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error('no text at y '..tostring(y))
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end
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for i,s in ipairs(App.screen.contents[screen_row]) do
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contents = contents..s
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end
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check_eq(contents, expected_contents, msg)
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end
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function colortable(app_color)
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return {app_color.r, app_color.g, app_color.b, app_color.a}
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end
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-- If you access the time using App.getTime instead of love.timer.getTime,
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-- tests will be able to move the time back and forwards as needed using
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-- App.wait_fake_time below.
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App.time = 1
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function App.getTime()
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@ -214,6 +185,11 @@ function App.width(text)
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return love.graphics.getFont():getWidth(text)
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end
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-- If you access the clipboard using App.getClipboardText and
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-- App.setClipboardText instead of love.system.getClipboardText and
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-- love.system.setClipboardText respectively, tests will be able to manipulate
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-- the clipboard by reading/writing App.clipboard.
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App.clipboard = ''
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function App.getClipboardText()
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return App.clipboard
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@ -222,28 +198,34 @@ function App.setClipboardText(s)
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App.clipboard = s
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end
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-- In tests I mostly send chords all at once to the keyboard handlers.
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-- However, you'll occasionally need to check if a key is down outside a handler.
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-- If you use App.key_down instead of love.keyboard.isDown, tests will be able to
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-- simulate keypresses using App.fake_key_press and App.fake_key_release
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-- below. This isn't very realistic, though, and it's up to tests to
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-- orchestrate key presses that correspond to the handlers they invoke.
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App.fake_keys_pressed = {}
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function App.key_down(key)
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return App.fake_keys_pressed[key]
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end
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function App.fake_key_press(key)
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App.fake_keys_pressed[key] = true
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end
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function App.fake_key_release(key)
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App.fake_keys_pressed[key] = nil
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end
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function App.key_down(key)
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return App.fake_keys_pressed[key]
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end
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-- Tests mostly will invoke mouse handlers directly. However, you'll
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-- occasionally need to check if a mouse button is down outside a handler.
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-- If you use App.mouse_down instead of love.mouse.isDown, tests will be able to
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-- simulate mouse clicks using App.fake_mouse_press and App.fake_mouse_release
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-- below. This isn't very realistic, though, and it's up to tests to
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-- orchestrate presses that correspond to the handlers they invoke.
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App.fake_mouse_state = {x=-1, y=-1} -- x,y always set
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function App.fake_mouse_press(x,y, mouse_button)
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App.fake_mouse_state.x = x
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App.fake_mouse_state.y = y
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App.fake_mouse_state[mouse_button] = true
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end
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function App.fake_mouse_release(x,y, mouse_button)
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App.fake_mouse_state.x = x
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App.fake_mouse_state.y = y
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App.fake_mouse_state[mouse_button] = nil
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end
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function App.mouse_move(x,y)
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App.fake_mouse_state.x = x
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App.fake_mouse_state.y = y
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@ -258,6 +240,60 @@ function App.mouse_y()
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return App.fake_mouse_state.y
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end
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function App.fake_mouse_press(x,y, mouse_button)
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App.fake_mouse_state.x = x
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App.fake_mouse_state.y = y
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App.fake_mouse_state[mouse_button] = true
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end
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function App.fake_mouse_release(x,y, mouse_button)
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App.fake_mouse_state.x = x
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App.fake_mouse_state.y = y
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App.fake_mouse_state[mouse_button] = nil
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end
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-- If you use App.open_for_reading and App.open_for_writing instead of other
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-- various Lua and LÖVE helpers, tests will be able to check the results of
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-- file operations inside the App.filesystem table.
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function App.open_for_writing(filename)
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App.filesystem[filename] = ''
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if Current_app == nil or Current_app == 'run' then
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return {
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write = function(self, ...)
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local args = {...}
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for i,s in ipairs(args) do
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App.filesystem[filename] = App.filesystem[filename]..s
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end
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end,
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close = function(self)
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end,
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}
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elseif Current_app == 'source' then
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return {
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write = function(self, s)
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App.filesystem[filename] = App.filesystem[filename]..s
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end,
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close = function(self)
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end,
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}
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end
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end
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function App.open_for_reading(filename)
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if App.filesystem[filename] then
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return {
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lines = function(self)
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return App.filesystem[filename]:gmatch('[^\n]+')
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end,
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close = function(self)
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end,
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}
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end
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end
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-- Some helpers to trigger an event and then refresh the screen. Akin to one
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-- iteration of the event loop.
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-- all textinput events are also keypresses
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-- TODO: handle chords of multiple keys
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function App.run_after_textinput(t)
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@ -300,74 +336,14 @@ function App.run_after_mouse_release(x,y, mouse_button)
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App.draw()
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end
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function App.screen.check(y, expected_contents, msg)
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--? print('checking for "'..expected_contents..'" at y '..tostring(y))
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local screen_row = 'y'..tostring(y)
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local contents = ''
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if App.screen.contents[screen_row] == nil then
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error('no text at y '..tostring(y))
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end
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for i,s in ipairs(App.screen.contents[screen_row]) do
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contents = contents..s
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end
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check_eq(contents, expected_contents, msg)
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-- miscellaneous internal helpers
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function App.color(color)
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love.graphics.setColor(color.r, color.g, color.b, color.a)
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end
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-- fake files
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function App.open_for_writing(filename)
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App.filesystem[filename] = ''
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if Current_app == nil or Current_app == 'run' then
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return {
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write = function(self, ...)
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local args = {...}
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for i,s in ipairs(args) do
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App.filesystem[filename] = App.filesystem[filename]..s
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end
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end,
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close = function(self)
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end,
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}
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elseif Current_app == 'source' then
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return {
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write = function(self, s)
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App.filesystem[filename] = App.filesystem[filename]..s
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end,
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close = function(self)
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end,
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}
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end
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end
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function App.open_for_reading(filename)
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if App.filesystem[filename] then
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return {
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lines = function(self)
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return App.filesystem[filename]:gmatch('[^\n]+')
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end,
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close = function(self)
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end,
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}
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end
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end
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function App.run_tests()
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local sorted_names = {}
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for name,binding in pairs(_G) do
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if name:find('test_') == 1 then
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table.insert(sorted_names, name)
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end
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end
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table.sort(sorted_names)
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for _,name in ipairs(sorted_names) do
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App.initialize_for_test()
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--? print('=== '..name)
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--? _G[name]()
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xpcall(_G[name], function(err) prepend_debug_info_to_test_failure(name, err) end)
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end
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-- clean up all test methods
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for _,name in ipairs(sorted_names) do
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_G[name] = nil
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end
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function colortable(app_color)
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return {app_color.r, app_color.g, app_color.b, app_color.a}
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end
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-- prepend file/line/test
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