diff --git a/Makefile b/Makefile
index c1bbf1c..7b02c9e 100644
--- a/Makefile
+++ b/Makefile
@@ -24,5 +24,5 @@ format:
 
 .PHONY: spec
 spec: format
-	./crystal spec --warnings all --error-on-warnings
+	./crystal spec --no-debug --warnings all --error-on-warnings
 
diff --git a/spec/expansion_spec.cr b/spec/expansion_spec.cr
index 5ed968c..e323584 100644
--- a/spec/expansion_spec.cr
+++ b/spec/expansion_spec.cr
@@ -1,4 +1,4 @@
-require "spec"
+require "./spec_helper"
 require "./../src/map"
 require "./../src/queue"
 
diff --git a/spec/queue_spec.cr b/spec/queue_spec.cr
index 687b582..cae01c6 100644
--- a/spec/queue_spec.cr
+++ b/spec/queue_spec.cr
@@ -1,4 +1,4 @@
-require "spec"
+require "./spec_helper"
 require "./../src/queue"
 require "./../src/command"
 
diff --git a/spec/world_spec.cr b/spec/world_spec.cr
new file mode 100644
index 0000000..176a1bc
--- /dev/null
+++ b/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
diff --git a/src/world.cr b/src/world.cr
index adc83c1..79e84bd 100644
--- a/src/world.cr
+++ b/src/world.cr
@@ -1,3 +1,5 @@
+require "./resources"
+
 class World
   property ts : Int32
 
@@ -15,7 +17,6 @@ class World
   def push(command : Command)
     dur = command.start(self)
     done_at = @ts + dur
-    printf "world : %d : plan `%s` at %d\n", @ts, typeof(command), done_at
     @tasks.push(done_at, command)
   end
 
@@ -28,7 +29,6 @@ class World
       command = item.command
       @ts = item.ts
       command.finish(self)
-      printf "world : %d : finish `%s`\n", @ts, typeof(command)
     end
   end
 end