Update engine tasks to self-sort and more unit tests

engine/src/main/kotlin/rs/dusk/engine/Engine.kt

@@ -30,7 +30,6 @@ class Engine {
 
     fun start() {
         val tasks: EngineTasks = get()
-        tasks.sort()
         val tick = Tick(tasks)
         executor.scheduleAtFixedRate(tick, ENGINE_DELAY, ENGINE_DELAY, TimeUnit.MILLISECONDS)
     }

engine/src/main/kotlin/rs/dusk/engine/EngineTasks.kt

@@ -1,12 +1,13 @@
 package rs.dusk.engine
 
 import org.koin.dsl.module
+import java.util.*
 
 /**
  * @author Greg Hibberd <greg@greghibberd.com>
  * @since April 22, 2020
  */
-data class EngineTasks(val data: MutableList<EngineTask> = mutableListOf()) : MutableList<EngineTask> by data
+data class EngineTasks(val data: TreeSet<EngineTask> = TreeSet()) : MutableSet<EngineTask> by data
 
 val engineModule = module {
     single { EngineTasks() }

engine/src/test/kotlin/rs/dusk/engine/EngineTaskTest.kt

@@ -0,0 +1,47 @@
+package rs.dusk.engine
+
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Test
+import org.koin.core.get
+import org.koin.dsl.module
+import rs.dusk.engine.script.KoinMock
+
+/**
+ * @author Greg Hibberd <greg@greghibberd.com>
+ * @since May 03, 2020
+ */
+internal class EngineTaskTest : KoinMock() {
+
+    private class TestTask(tasks: EngineTasks, priority: Int) : EngineTask(tasks, priority) {
+        override fun run() {
+        }
+    }
+
+    override val modules = listOf(engineModule, module {
+        single { TestTask(get(), 1) }
+    })
+
+    @Test
+    fun `Adds self to task list`() {
+        // Given
+        val tasks: EngineTasks = get()
+        val updateTask: TestTask = get()
+        // Then
+        assert(tasks.contains(updateTask))
+    }
+
+    @Test
+    fun `Multiple tasks are ordered by priority`() {
+        // Given
+        val tasks: EngineTasks = get()
+        val third = TestTask(tasks, 1)
+        val first = TestTask(tasks, 3)
+        val second = TestTask(tasks, 2)
+        // Then
+        val expected = listOf(first, second, third)
+        tasks.data.forEachIndexed { index, task ->
+            assertEquals(expected[index], task)
+        }
+    }
+
+}

engine/src/test/kotlin/rs/dusk/engine/ParallelEngineTaskTest.kt

@@ -0,0 +1,34 @@
+package rs.dusk.engine
+
+import kotlinx.coroutines.GlobalScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.delay
+import org.junit.jupiter.api.Test
+import kotlin.system.measureTimeMillis
+
+/**
+ * @author Greg Hibberd <greg@greghibberd.com>
+ * @since May 03, 2020
+ */
+internal class ParallelEngineTaskTest {
+
+    private class TestTask(tasks: EngineTasks) : ParallelEngineTask(tasks)
+
+    @Test
+    fun `Tasks run in parallel`() {
+        // Given
+        val tasks = EngineTasks()
+        val first = TestTask(tasks)
+        first.defers.add(GlobalScope.async {
+            delay(100)
+        })
+        first.defers.add(GlobalScope.async {
+            delay(100)
+        })
+        // When
+        val took = measureTimeMillis {
+            first.run()
+        }
+        assert(took < 200)// This could be temperamental
+    }
+}

engine/src/test/kotlin/rs/dusk/engine/client/update/PreUpdateEncodingTaskTest.kt

@@ -10,7 +10,6 @@ import org.koin.core.qualifier.named
 import org.koin.dsl.module
 import rs.dusk.core.io.read.BufferReader
 import rs.dusk.core.io.write.BufferWriter
-import rs.dusk.engine.EngineTasks
 import rs.dusk.engine.engineModule
 import rs.dusk.engine.entity.list.entityListModule
 import rs.dusk.engine.entity.list.npc.NPCs
@@ -43,14 +42,6 @@ internal class PreUpdateEncodingTaskTest : KoinMock() {
 
     override val modules = listOf(engineModule, entityListModule, clientUpdateModule, encoderModule)
 
-    @Test
-    fun `Adds self to task list`() {
-        // Given
-        val tasks: EngineTasks = get()
-        val updateTask: PreUpdateEncodingTask = get()
-        // Then
-        assert(tasks.contains(updateTask))
-    }
 
     @Test
     fun `Run runs all in parallel`() {