Add small world test

spec/expansion_spec.cr

@@ -1,4 +1,4 @@
-require "spec"
+require "./spec_helper"
 require "./../src/map"
 require "./../src/queue"
 

spec/queue_spec.cr

@@ -1,4 +1,4 @@
-require "spec"
+require "./spec_helper"
 require "./../src/queue"
 require "./../src/command"
 

spec/world_spec.cr

@@ -0,0 +1,13 @@
+require "./spec_helper"
+require "../src/world"
+
+describe "World" do
+  it "should build crystal harvester" do
+    world = World.new
+    point = Point.new(2, 3)
+    cmd = BuildCrystalHarvesterCommand.new(point)
+    world.push(cmd)
+    world.run(100)
+    world.map.get(point).has_role(TileRole::CrystalHarvester)
+  end
+end