OpenGL TestExample (Kotlin)

interface Context {
    fun init()
    fun destroy()
} // subset of opengl.Context methods

class OpenGLContext : Context {
    // wrapper for OpenGLContext
    // holds logic and possible interactions with opengl.Context
    // but hides so much as possible

    override fun init() {
        if (opengl.getContext() != null) {
            throw IllegalStateException("context is already initalized")
        }

        opengl.init()
    }

    override fun destroy() {
        if (opengl.getContext() == null) {
            throw IllegalStateException("context is alredy destroyed")
        }

        opengl.destroy()
    }
}

// GameEngine doesn't have to know it uses OpenGLContext,
// knows only about Context from the app
// and it doesn't care about the static shit in the 3rd party library
class GameEngine(private val context: Context) {
    fun stop() {
        // ...
        this.context.destroy()
    }
}

fun GameEngineRunning_Stop_DestroyContext() {
     // given
     val contextMock = mockk.Create<Context>()
     val engine = GameEngine(contextMock)

     // when
     engine.stop()

     // then
     verify(exactly = 1) {
         contextMock.destroy()
     }
}