add plusAssign/minusAssign of EntityBag to MutableEntityBag

src/commonMain/kotlin/com/github/quillraven/fleks/collection/entityBag.kt

@@ -463,6 +463,20 @@ class MutableEntityBag(
         }
     }
 
+    /**
+     * Adds all [entities] to the bag. If the [capacity] is not sufficient then a resize is happening.
+     */
+    operator fun plusAssign(entities: EntityBag) {
+        entities.forEach { plusAssign(it) }
+    }
+
+    /**
+     * Removes all [entities] of the bag.
+     */
+    operator fun minusAssign(entities: EntityBag) {
+        entities.forEach { minusAssign(it) }
+    }
+
     /**
      * Resets [size] to zero and clears any [entity][Entity] of the bag.
      */

src/commonTest/kotlin/com/github/quillraven/fleks/collection/EntityBagTest.kt

@@ -648,4 +648,34 @@ class EntityBagTest {
         bag = mutableEntityBagOf()
         assertEquals(0, bag.size)
     }
+
+    @Test
+    fun `test plusAssign of an EntityBag`() {
+        val bag = mutableEntityBagOf()
+        val toAdd = entityBagOf(testEntity1, testEntity2)
+
+        bag += toAdd
+
+        assertEquals(2, bag.size)
+        assertTrue { testEntity1 in bag }
+        assertTrue { testEntity2 in bag }
+    }
+
+    @Test
+    fun `test minusAssign of an EntityBag`() {
+        val bag = mutableEntityBagOf()
+        val toRemove = entityBagOf(testEntity1, testEntity2)
+
+        // remove of empty bag does nothing
+        bag -= toRemove
+        assertEquals(0, bag.size)
+
+        bag += testEntity2
+        bag += testEntity1
+        assertEquals(2, bag.size)
+        bag -= toRemove
+        assertEquals(0, bag.size)
+        assertFalse { testEntity1 in bag }
+        assertFalse { testEntity2 in bag }
+    }
 }