Add some tests.

tests/TEST_init.py

@@ -0,0 +1,15 @@
+from .__init__ import sdl3, TEST_RegisterFunction
+
+@TEST_RegisterFunction
+def TEST_SDL_Init():
+    assert sdl3.SDL_Init(0), "SDL_Init failed."
+    assert sdl3.SDL_GetError() == "".encode(), "SDL_GetError failed."
+    sdl3.SDL_Quit()
+
+@TEST_RegisterFunction
+def TEST_SDL_CreateWindow():
+    assert sdl3.SDL_Init(sdl3.SDL_INIT_VIDEO), "SDL_Init failed."
+    assert (window := sdl3.SDL_CreateWindow("Test".encode(), 1600, 900, sdl3.SDL_WINDOW_RESIZABLE)), "SDL_CreateWindow failed."
+    assert sdl3.SDL_GetError() == "".encode(), "SDL_GetError failed."
+    sdl3.SDL_DestroyWindow(window)
+    sdl3.SDL_Quit()

tests/__init__.py

@@ -0,0 +1,30 @@
+import os, sys, atexit
+
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..")))
+
+import sdl3
+
+functions = []
+
+def TEST_RegisterFunction(func):
+    functions.append(func)
+
+from tests.TEST_init import *
+
+@atexit.register
+def TEST_RunAllTests():
+    if not functions: return
+    successful, failed = 0, 0
+
+    for func in functions:
+        try:
+            func()
+            print("\33[32m", f"Test '{func.__name__}' passed.", "\33[0m", sep = "", flush = True)
+            successful += 1
+
+        except AssertionError as error:
+            print("\33[31m", f"Test '{func.__name__}' failed: {error}", "\33[0m", sep = "", flush = True)
+            failed += 1
+
+    print("\33[35m", f"{successful} tests passed, {failed} tests failed.", "\33[0m", sep = "", flush = True)
+    assert not failed, "There are some failed tests."