diff --git a/src/Mujoco/MJCF.purs b/src/Mujoco/MJCF.purs
index a4f9d20..646b942 100644
--- a/src/Mujoco/MJCF.purs
+++ b/src/Mujoco/MJCF.purs
@@ -32,6 +32,9 @@ import Mujoco.MJCF.Keyword as X
 import Mujoco.MJCF.Asset as X
 import Mujoco.MJCF.Body as X
 import Mujoco.MJCF.Contact as X
+import Mujoco.MJCF.Sensor (sensor) as X
+import Mujoco.MJCF.Actuator (actuator) as X
+import Mujoco.MJCF.Tendon (tendon) as X
 import Mujoco.MJCF.XML (empty, text, fragment) as X
 
 type Props_mujoco = (model :: String)
diff --git a/src/Mujoco/MJCF/Sensor.purs b/src/Mujoco/MJCF/Sensor.purs
index fd24cad..1b9e6b8 100644
--- a/src/Mujoco/MJCF/Sensor.purs
+++ b/src/Mujoco/MJCF/Sensor.purs
@@ -4,6 +4,8 @@ import Mujoco.MJCF.Prelude
 
 import Mujoco.MJCF.Keyword as Kw
 
+sensor = tag @() "sensor" :: Tag ()
+
 type ObjType = Kw.Body \/ Kw.Xbody \/ Kw.Geom \/ Kw.Site \/ Kw.Camera
 
 type Common' r =
diff --git a/src/Mujoco/MJCF/Tendon.purs b/src/Mujoco/MJCF/Tendon.purs
index 8ebf5d9..dee7416 100644
--- a/src/Mujoco/MJCF/Tendon.purs
+++ b/src/Mujoco/MJCF/Tendon.purs
@@ -4,6 +4,8 @@ import Mujoco.MJCF.Prelude
 
 import Mujoco.MJCF.Keyword as Kw
 
+tendon = tag @() "tendon" :: Tag ()
+
 type Common r =
   ( class :: String
   , group :: Int
diff --git a/src/Mujoco/MJCF/XML.Prop.purs b/src/Mujoco/MJCF/XML.Prop.purs
index a0a2ae8..a49a987 100644
--- a/src/Mujoco/MJCF/XML.Prop.purs
+++ b/src/Mujoco/MJCF/XML.Prop.purs
@@ -20,7 +20,7 @@ import Type.Prelude (Proxy(..))
 import Unsafe.Coerce (unsafeCoerce)
 
 renames :: Map String String
-renames = Map.fromFoldable ["size" /\ "mjcf:size"]
+renames = Map.fromFoldable ["size" /\ "mjcf:size", "class" /\ "mjcf:class"]
 
 class Serialize a where
   serialize :: a -> String
diff --git a/test/Main.purs b/test/Main.purs
index fa5edd0..6c8cb48 100644
--- a/test/Main.purs
+++ b/test/Main.purs
@@ -3,13 +3,36 @@ module Test.Main where
 import Prelude
 
 import Effect (Effect)
-import Test.Mujoco.MJCF.XML.Prop as Test.Mujoco.MJCF.XML.Prop
 import Test.Mujoco.MJCF as Test.Mujoco.MJCF
+import Test.Mujoco.MJCF.Actuator as Test.Mujoco.MJCF.Actuator
+import Test.Mujoco.MJCF.Contact as Test.Mujoco.MJCF.Contact
+import Test.Mujoco.MJCF.Custom as Test.Mujoco.MJCF.Custom
+import Test.Mujoco.MJCF.Default as Test.Mujoco.MJCF.Default
+import Test.Mujoco.MJCF.Deformable as Test.Mujoco.MJCF.Deformable
+import Test.Mujoco.MJCF.Equality as Test.Mujoco.MJCF.Equality
+import Test.Mujoco.MJCF.Keyframe as Test.Mujoco.MJCF.Keyframe
+import Test.Mujoco.MJCF.Sensor as Test.Mujoco.MJCF.Sensor
+import Test.Mujoco.MJCF.Tendon as Test.Mujoco.MJCF.Tendon
+import Test.Mujoco.MJCF.Visual as Test.Mujoco.MJCF.Visual
+import Test.Mujoco.MJCF.XML.Prop as Test.Mujoco.MJCF.XML.Prop
+import Test.Mujoco.MJCF.Util (mjcf)
+import Test.Spec (mapSpecTree)
 import Test.Spec.Reporter.Console (consoleReporter)
 import Test.Spec.Runner.Node (runSpecAndExitProcess)
 
 main :: Effect Unit
 main =
   runSpecAndExitProcess [consoleReporter] do
-    Test.Mujoco.MJCF.spec
-    Test.Mujoco.MJCF.XML.Prop.spec
+    mjcf do
+      Test.Mujoco.MJCF.spec
+      Test.Mujoco.MJCF.XML.Prop.spec
+      Test.Mujoco.MJCF.Actuator.spec
+      Test.Mujoco.MJCF.Contact.spec
+      Test.Mujoco.MJCF.Custom.spec
+      Test.Mujoco.MJCF.Deformable.spec
+      Test.Mujoco.MJCF.Default.spec
+      Test.Mujoco.MJCF.Equality.spec
+      Test.Mujoco.MJCF.Keyframe.spec
+      Test.Mujoco.MJCF.Sensor.spec
+      Test.Mujoco.MJCF.Tendon.spec
+      Test.Mujoco.MJCF.Visual.spec
diff --git a/test/Mujoco.MJCF.Actuator.purs b/test/Mujoco.MJCF.Actuator.purs
new file mode 100644
index 0000000..7eb62a6
--- /dev/null
+++ b/test/Mujoco.MJCF.Actuator.purs
@@ -0,0 +1,102 @@
+module Test.Mujoco.MJCF.Actuator where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Actuator as Act
+import Mujoco.MJCF.XML (Node)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+-- | Model with a body + hinge joint for actuator tests
+m :: Node -> Node
+m a = X.mujoco {}
+  [ X.compiler { inertiafromgeom: X.true_ }
+  , X.worldbody {}
+      [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+          ]
+      ]
+  , a
+  ]
+
+spec :: MjcfSpec Unit
+spec =
+  describe "actuator" do
+    describe "general" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.general { name: "a_gen", joint: "j1" } ]
+
+      it "dyntype + gaintype + biastype" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.general { name: "a_gen2", joint: "j1", dyntype: X.kw X.Filter, gaintype: X.kw X.Fixed, biastype: X.kw X.Affine } ]
+
+      it "ctrlrange + forcerange" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.general { name: "a_gen3", joint: "j1", ctrllimited: X.true_, ctrlrange: (-1.0) /\ 1.0, forcelimited: X.true_, forcerange: (-100.0) /\ 100.0 } ]
+
+    describe "motor" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.motor { name: "a_motor", joint: "j1" } ]
+
+      it "ctrlrange + gear" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.motor { name: "a_motor2", joint: "j1", ctrllimited: X.true_, ctrlrange: (-1.0) /\ 1.0, gear: [100.0, 0.0, 0.0, 0.0, 0.0, 0.0] } ]
+
+    describe "position" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.position { name: "a_pos", joint: "j1" } ]
+
+      it "kp + kv" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.position { name: "a_pos2", joint: "j1", kp: 100.0, kv: 10.0 } ]
+
+    describe "velocity" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.velocity { name: "a_vel", joint: "j1" } ]
+
+      it "kv" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.velocity { name: "a_vel2", joint: "j1", kv: 10.0 } ]
+
+    describe "intvelocity" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.intvelocity { name: "a_iv", joint: "j1" } ]
+
+      it "kp + actrange" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.intvelocity { name: "a_iv2", joint: "j1", kp: 100.0, actrange: (-1.0) /\ 1.0 } ]
+
+    describe "damper" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.damper { name: "a_damp", joint: "j1" } ]
+
+      it "kv" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.damper { name: "a_damp2", joint: "j1", kv: 10.0 } ]
+
+    describe "cylinder" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.cylinder { name: "a_cyl", joint: "j1" } ]
+
+      it "timeconst + area" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.cylinder { name: "a_cyl2", joint: "j1", timeconst: 0.1, area: 0.01 } ]
+
+    describe "muscle" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.muscle { name: "a_musc", joint: "j1" } ]
+
+      it "force + range + timeconst" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.muscle { name: "a_musc2", joint: "j1", force: 100.0, range: 0.75 /\ 1.05, timeconst: 0.01 /\ 0.04 } ]
+
+    describe "adhesion" do
+      it "basic" $ parseOk $ m $
+        Act.actuator {} [ Act.adhesion { name: "a_adh", body: "b1" } ]
+
+      it "gain" $ parseOk $ m $
+        Act.actuator {}
+          [ Act.adhesion { name: "a_adh2", body: "b1", gain: 1.0 } ]
diff --git a/test/Mujoco.MJCF.Contact.purs b/test/Mujoco.MJCF.Contact.purs
new file mode 100644
index 0000000..5999106
--- /dev/null
+++ b/test/Mujoco.MJCF.Contact.purs
@@ -0,0 +1,47 @@
+module Test.Mujoco.MJCF.Contact where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+spec :: MjcfSpec Unit
+spec =
+  describe "contact" do
+    describe "pair" do
+      it "geom1 + geom2" $ parseOk $ X.mujoco {}
+        [ X.worldbody {}
+            [ X.geom { name: "g1", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+            , X.geom { name: "g2", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0], pos: 1.0 /\ 0.0 /\ 0.0 } unit
+            ]
+        , X.contact {} [ X.pair { geom1: "g1", geom2: "g2" } ]
+        ]
+
+      it "condim + friction" $ parseOk $ X.mujoco {}
+        [ X.worldbody {}
+            [ X.geom { name: "g1", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+            , X.geom { name: "g2", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0], pos: 1.0 /\ 0.0 /\ 0.0 } unit
+            ]
+        , X.contact {} [ X.pair { geom1: "g1", geom2: "g2", condim: 3, friction: 1.0 /\ 0.005 /\ 0.0001 /\ 0.005 /\ 0.0001 } ]
+        ]
+
+      it "solref + solimp + margin + gap" $ parseOk $ X.mujoco {}
+        [ X.worldbody {}
+            [ X.geom { name: "g1", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+            , X.geom { name: "g2", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0], pos: 1.0 /\ 0.0 /\ 0.0 } unit
+            ]
+        , X.contact {} [ X.pair { geom1: "g1", geom2: "g2", solref: 0.02 /\ 1.0, solimp: 0.9 /\ 0.95 /\ 0.001 /\ 0.5 /\ 2.0, margin: 0.01, gap: 0.0 } ]
+        ]
+
+    describe "exclude" do
+      it "body1 + body2" $ parseOk $ X.mujoco {}
+        [ X.worldbody {}
+            [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            , X.body { name: "b2", pos: 1.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        , X.contact {} [ X.exclude { body1: "b1", body2: "b2" } ]
+        ]
diff --git a/test/Mujoco.MJCF.Custom.purs b/test/Mujoco.MJCF.Custom.purs
new file mode 100644
index 0000000..cd3d62b
--- /dev/null
+++ b/test/Mujoco.MJCF.Custom.purs
@@ -0,0 +1,50 @@
+module Test.Mujoco.MJCF.Custom where
+
+import Prelude
+
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Custom as Custom
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+spec :: MjcfSpec Unit
+spec =
+  describe "custom" do
+    describe "numeric" do
+      it "name + data" $ parseOk $ X.mujoco {}
+        [ Custom.custom {}
+            [ Custom.numeric { name: "params", data: [1.0, 2.0, 3.0] } ]
+        , X.worldbody {} unit
+        ]
+
+      it "name + size" $ parseOk $ X.mujoco {}
+        [ Custom.custom {}
+            [ Custom.numeric { name: "zeros", size: 5 } ]
+        , X.worldbody {} unit
+        ]
+
+    describe "text" do
+      it "name + data" $ parseOk $ X.mujoco {}
+        [ Custom.custom {}
+            [ Custom.text { name: "info", data: "hello world" } ]
+        , X.worldbody {} unit
+        ]
+
+    describe "tuple" do
+      it "with elements" $ parseOk $ X.mujoco {}
+        [ Custom.custom {}
+            [ Custom.tuple { name: "body_list" }
+                [ Custom.element { objtype: "body", objname: "world", prm: 1.0 } ]
+            ]
+        , X.worldbody {} unit
+        ]
+
+    describe "mixed" do
+      it "numeric + text + tuple" $ parseOk $ X.mujoco {}
+        [ Custom.custom {}
+            [ Custom.numeric { name: "n1", data: [0.0] }
+            , Custom.text { name: "t1", data: "value" }
+            , Custom.tuple { name: "tup1" } unit
+            ]
+        , X.worldbody {} unit
+        ]
diff --git a/test/Mujoco.MJCF.Default.purs b/test/Mujoco.MJCF.Default.purs
new file mode 100644
index 0000000..f357c17
--- /dev/null
+++ b/test/Mujoco.MJCF.Default.purs
@@ -0,0 +1,87 @@
+module Test.Mujoco.MJCF.Default where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Default as Def
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+spec :: MjcfSpec Unit
+spec =
+  describe "default" do
+    it "empty" $ parseOk $ X.mujoco {}
+      [ Def.default {} unit
+      , X.worldbody {} unit
+      ]
+
+    it "with class" $ parseOk $ X.mujoco {}
+      [ Def.default { class: "main" } unit
+      , X.worldbody {} unit
+      ]
+
+    it "geom defaults" $ parseOk $ X.mujoco {}
+      [ Def.default {}
+          [ Def.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0], rgba: 1.0 /\ 0.0 /\ 0.0 /\ 1.0 } ]
+      , X.worldbody {}
+          [ X.geom {} unit ]
+      ]
+
+    it "joint defaults" $ parseOk $ X.mujoco {}
+      [ X.compiler { inertiafromgeom: X.true_ }
+      , Def.default {}
+          [ Def.joint { type: X.kw X.Hinge, damping: 1.0, stiffness: 10.0 }
+          , Def.geom { type: X.kw X.Capsule, size: [0.05, 0.2] }
+          ]
+      , X.worldbody {}
+          [ X.body { pos: 0.0 /\ 0.0 /\ 0.5 }
+              [ X.joint { axis: 1.0 /\ 0.0 /\ 0.0 }
+              , X.geom {} unit
+              ]
+          ]
+      ]
+
+    it "nested defaults" $ parseOk $ X.mujoco {}
+      [ X.compiler { inertiafromgeom: X.true_ }
+      , Def.default { class: "outer" }
+          [ Def.geom { rgba: 1.0 /\ 1.0 /\ 1.0 /\ 1.0 }
+          , Def.default { class: "inner" }
+              [ Def.geom { rgba: 1.0 /\ 0.0 /\ 0.0 /\ 1.0 } ]
+          ]
+      , X.worldbody {}
+          [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+      ]
+
+    it "site defaults" $ parseOk $ X.mujoco {}
+      [ Def.default {}
+          [ Def.site { type: X.kw X.Sphere, size: 0.02 /\ 0.02 /\ 0.02, rgba: 0.0 /\ 1.0 /\ 0.0 /\ 1.0 } ]
+      , X.worldbody {}
+          [ X.site { name: "s1", pos: 0.0 /\ 0.0 /\ 0.0 } ]
+      ]
+
+    it "light defaults" $ parseOk $ X.mujoco {}
+      [ Def.default {}
+          [ Def.light { diffuse: 0.8 /\ 0.8 /\ 0.8, castshadow: true } ]
+      , X.worldbody {}
+          [ X.light { name: "l1", pos: 0.0 /\ 0.0 /\ 3.0 } ]
+      ]
+
+    it "camera defaults" $ parseOk $ X.mujoco {}
+      [ Def.default {}
+          [ Def.camera { fovy: 60.0 } ]
+      , X.worldbody {}
+          [ X.camera { name: "c1", pos: 0.0 /\ (-2.0) /\ 1.0 } ]
+      ]
+
+    it "motor defaults" $ parseOk $ X.mujoco {}
+      [ X.compiler { inertiafromgeom: X.true_ }
+      , Def.default {}
+          [ Def.motor { ctrllimited: X.true_, ctrlrange: (-1.0) /\ 1.0 } ]
+      , X.worldbody {}
+          [ X.body { pos: 0.0 /\ 0.0 /\ 0.5 }
+              [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+              , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+              ]
+          ]
+      ]
diff --git a/test/Mujoco.MJCF.Deformable.purs b/test/Mujoco.MJCF.Deformable.purs
new file mode 100644
index 0000000..caf9ed6
--- /dev/null
+++ b/test/Mujoco.MJCF.Deformable.purs
@@ -0,0 +1,92 @@
+module Test.Mujoco.MJCF.Deformable where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Deformable as Deformable
+import Mujoco.MJCF.Deformable.Flex as Flex
+import Mujoco.MJCF.Deformable.Skin as Skin
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+spec :: MjcfSpec Unit
+spec =
+  describe "deformable" do
+    describe "flex" do
+      it "basic" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , Deformable.deformable {}
+            [ Flex.flex { name: "f1", dim: 3, vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0], element: [0, 1, 2, 3] }
+                unit
+            ]
+        , X.worldbody {}
+            [ X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        ]
+
+      it "with edge" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , Deformable.deformable {}
+            [ Flex.flex { name: "f2", dim: 3, vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0], element: [0, 1, 2, 3] }
+                [ Flex.edge { stiffness: 100.0, damping: 1.0 } ]
+            ]
+        , X.worldbody {}
+            [ X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        ]
+
+      it "with elasticity" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , Deformable.deformable {}
+            [ Flex.flex { name: "f3", dim: 3, vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0], element: [0, 1, 2, 3] }
+                [ Flex.elasticity { young: 1000.0, poisson: 0.3, damping: 0.01 } ]
+            ]
+        , X.worldbody {}
+            [ X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        ]
+
+      it "with contact" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , Deformable.deformable {}
+            [ Flex.flex { name: "f4", dim: 3, vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0], element: [0, 1, 2, 3] }
+                [ Flex.contact { internal: true } ]
+            ]
+        , X.worldbody {}
+            [ X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        ]
+
+      it "rgba + group" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , Deformable.deformable {}
+            [ Flex.flex { name: "f5", dim: 3, vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0], element: [0, 1, 2, 3], rgba: 1.0 /\ 0.0 /\ 0.0 /\ 1.0, group: 0 }
+                unit
+            ]
+        , X.worldbody {}
+            [ X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
+                [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit ]
+            ]
+        ]
+
+    describe "skin" do
+      it "basic" $ parseOk $ X.mujoco {}
+        [ Deformable.deformable {}
+            [ Skin.skin { name: "sk1", vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0], face: [0, 1, 2] }
+                [ Skin.bone { body: "world", bindpos: 0.0 /\ 0.0 /\ 0.0, bindquat: 1.0 /\ 0.0 /\ 0.0 /\ 0.0, vertid: [0, 1, 2], vertweight: [1.0, 1.0, 1.0] } ]
+            ]
+        , X.worldbody {} unit
+        ]
+
+      it "inflate + rgba" $ parseOk $ X.mujoco {}
+        [ Deformable.deformable {}
+            [ Skin.skin { name: "sk2", vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0], face: [0, 1, 2], inflate: 0.01, rgba: 0.5 /\ 0.5 /\ 1.0 /\ 0.8 }
+                [ Skin.bone { body: "world", bindpos: 0.0 /\ 0.0 /\ 0.0, bindquat: 1.0 /\ 0.0 /\ 0.0 /\ 0.0, vertid: [0, 1, 2], vertweight: [1.0, 1.0, 1.0] } ]
+            ]
+        , X.worldbody {} unit
+        ]
diff --git a/test/Mujoco.MJCF.Equality.purs b/test/Mujoco.MJCF.Equality.purs
new file mode 100644
index 0000000..d148363
--- /dev/null
+++ b/test/Mujoco.MJCF.Equality.purs
@@ -0,0 +1,73 @@
+module Test.Mujoco.MJCF.Equality where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Equality as Eq
+import Mujoco.MJCF.Tendon as Tendon
+import Mujoco.MJCF.XML (Node)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+-- | Model with two bodies, joints, and sites for equality constraint tests
+m :: Node -> Node
+m e = X.mujoco {}
+  [ X.compiler { inertiafromgeom: X.true_ }
+  , X.worldbody {}
+      [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+          , X.site { name: "s1", pos: 0.0 /\ 0.0 /\ 0.1, size: 0.01 /\ 0.01 /\ 0.01 }
+          ]
+      , X.body { name: "b2", pos: 1.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j2", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+          , X.site { name: "s2", pos: 0.0 /\ 0.0 /\ 0.1, size: 0.01 /\ 0.01 /\ 0.01 }
+          ]
+      ]
+  , e
+  ]
+
+spec :: MjcfSpec Unit
+spec =
+  describe "equality" do
+    describe "connect" do
+      it "body1 + body2 + anchor" $ parseOk $ m $
+        Eq.equality {} [ Eq.connect { body1: "b1", body2: "b2", anchor: 0.5 /\ 0.0 /\ 0.5 } unit ]
+
+      it "site1 + site2" $ parseOk $ m $
+        Eq.equality {} [ Eq.connect { site1: "s1", site2: "s2" } unit ]
+
+      it "solref + solimp" $ parseOk $ m $
+        Eq.equality {} [ Eq.connect { body1: "b1", body2: "b2", anchor: 0.5 /\ 0.0 /\ 0.5, solref: 0.02 /\ 1.0, solimp: 0.9 /\ 0.95 /\ 0.001 /\ 0.5 /\ 2.0 } unit ]
+
+    describe "weld" do
+      it "body1 + body2" $ parseOk $ m $
+        Eq.equality {} [ Eq.weld { body1: "b1", body2: "b2" } ]
+
+      it "site1 + site2" $ parseOk $ m $
+        Eq.equality {} [ Eq.weld { site1: "s1", site2: "s2" } ]
+
+      it "torquescale" $ parseOk $ m $
+        Eq.equality {} [ Eq.weld { body1: "b1", body2: "b2", torquescale: 1.0 } ]
+
+    describe "joint" do
+      it "joint1 + joint2" $ parseOk $ m $
+        Eq.equality {} [ Eq.joint { joint1: "j1", joint2: "j2" } ]
+
+      it "polycoef" $ parseOk $ m $
+        Eq.equality {} [ Eq.joint { joint1: "j1", joint2: "j2", polycoef: 0.0 /\ 1.0 /\ 0.0 /\ 0.0 /\ 0.0 } ]
+
+    describe "tendon" do
+      it "tendon1" $ parseOk $ X.mujoco {}
+        [ X.compiler { inertiafromgeom: X.true_ }
+        , X.worldbody {}
+            [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
+                [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+                , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+                ]
+            ]
+        , Tendon.tendon {} $ Tendon.fixed { name: "t1" } [ Tendon.joint { joint: "j1", coef: 1.0 } ]
+        , Eq.equality {} [ Eq.tendon { tendon1: "t1" } ]
+        ]
diff --git a/test/Mujoco.MJCF.Keyframe.purs b/test/Mujoco.MJCF.Keyframe.purs
new file mode 100644
index 0000000..70356b9
--- /dev/null
+++ b/test/Mujoco.MJCF.Keyframe.purs
@@ -0,0 +1,54 @@
+module Test.Mujoco.MJCF.Keyframe where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+spec :: MjcfSpec Unit
+spec =
+  describe "keyframe" do
+    it "empty" $ parseOk $ X.mujoco {}
+      [ X.worldbody {} unit
+      , X.keyframe {} unit
+      ]
+
+    it "key with time" $ parseOk $ X.mujoco {}
+      [ X.worldbody {} unit
+      , X.keyframe {}
+          [ X.key { name: "home", time: 0.0 } ]
+      ]
+
+    it "key with qpos + qvel" $ parseOk $ X.mujoco {}
+      [ X.compiler { inertiafromgeom: X.true_ }
+      , X.worldbody {}
+          [ X.body { pos: 0.0 /\ 0.0 /\ 0.5 }
+              [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+              , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+              ]
+          ]
+      , X.keyframe {}
+          [ X.key { name: "init", time: 0.0, qpos: [0.5], qvel: [0.0] } ]
+      ]
+
+    it "key with ctrl" $ parseOk $ X.mujoco {}
+      [ X.compiler { inertiafromgeom: X.true_ }
+      , X.worldbody {}
+          [ X.body { pos: 0.0 /\ 0.0 /\ 0.5 }
+              [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+              , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+              ]
+          ]
+      , X.keyframe {}
+          [ X.key { name: "start", ctrl: [0.0] } ]
+      ]
+
+    it "multiple keys" $ parseOk $ X.mujoco {}
+      [ X.worldbody {} unit
+      , X.keyframe {}
+          [ X.key { name: "k1", time: 0.0 }
+          , X.key { name: "k2", time: 1.0 }
+          ]
+      ]
diff --git a/test/Mujoco.MJCF.Sensor.purs b/test/Mujoco.MJCF.Sensor.purs
new file mode 100644
index 0000000..ca1f30f
--- /dev/null
+++ b/test/Mujoco.MJCF.Sensor.purs
@@ -0,0 +1,166 @@
+module Test.Mujoco.MJCF.Sensor where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Actuator as Act
+import Mujoco.MJCF.Sensor as Sens
+import Mujoco.MJCF.XML (Node)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+-- | Model with body, site, joint, tendon, and actuator for sensor tests
+m :: Node -> Node
+m s = X.mujoco {}
+  [ X.compiler { inertiafromgeom: X.true_ }
+  , X.worldbody {}
+      [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { name: "g1", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+          , X.site { name: "s1", pos: 0.0 /\ 0.0 /\ 0.1, size: 0.01 /\ 0.01 /\ 0.01 }
+          , X.camera { name: "cam1", pos: 0.0 /\ (-1.0) /\ 0.5, fovy: 60.0 }
+          ]
+      , X.body { name: "b2", pos: 1.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j2", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { name: "g2", type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
+          , X.site { name: "s2", pos: 0.0 /\ 0.0 /\ 0.1, size: 0.01 /\ 0.01 /\ 0.01 }
+          ]
+      ]
+  , Act.actuator {} [ Act.motor { name: "a1", joint: "j1" } ]
+  , s
+  ]
+
+spec :: MjcfSpec Unit
+spec =
+  describe "sensor" do
+    describe "site-based" do
+      it "touch" $ parseOk $ m $
+        X.sensor {} [ Sens.touch { name: "se_touch", site: "s1" } ]
+
+      it "accelerometer" $ parseOk $ m $
+        X.sensor {} [ Sens.accelerometer { name: "se_accel", site: "s1" } ]
+
+      it "velocimeter" $ parseOk $ m $
+        X.sensor {} [ Sens.velocimeter { name: "se_velo", site: "s1" } ]
+
+      it "gyro" $ parseOk $ m $
+        X.sensor {} [ Sens.gyro { name: "se_gyro", site: "s1" } ]
+
+      it "force" $ parseOk $ m $
+        X.sensor {} [ Sens.force { name: "se_force", site: "s1" } ]
+
+      it "torque" $ parseOk $ m $
+        X.sensor {} [ Sens.torque { name: "se_torque", site: "s1" } ]
+
+      it "magnetometer" $ parseOk $ m $
+        X.sensor {} [ Sens.magnetometer { name: "se_mag", site: "s1" } ]
+
+      it "rangefinder" $ parseOk $ m $
+        X.sensor {} [ Sens.rangefinder { name: "se_range", site: "s1" } ]
+
+      it "camprojection" $ parseOk $ m $
+        X.sensor {} [ Sens.camprojection { name: "se_camp", site: "s1", camera: "cam1" } ]
+
+    describe "joint-based" do
+      it "jointpos" $ parseOk $ m $
+        X.sensor {} [ Sens.jointpos { name: "se_jpos", joint: "j1" } ]
+
+      it "jointvel" $ parseOk $ m $
+        X.sensor {} [ Sens.jointvel { name: "se_jvel", joint: "j1" } ]
+
+      it "jointactuatorfrc" $ parseOk $ m $
+        X.sensor {} [ Sens.jointactuatorfrc { name: "se_jafrc", joint: "j1" } ]
+
+      it "jointlimitpos" $ parseOk $ m $
+        X.sensor {} [ Sens.jointlimitpos { name: "se_jlpos", joint: "j1" } ]
+
+      it "jointlimitvel" $ parseOk $ m $
+        X.sensor {} [ Sens.jointlimitvel { name: "se_jlvel", joint: "j1" } ]
+
+      it "jointlimitfrc" $ parseOk $ m $
+        X.sensor {} [ Sens.jointlimitfrc { name: "se_jlfrc", joint: "j1" } ]
+
+    describe "actuator-based" do
+      it "actuatorpos" $ parseOk $ m $
+        X.sensor {} [ Sens.actuatorpos { name: "se_apos", actuator: "a1" } ]
+
+      it "actuatorvel" $ parseOk $ m $
+        X.sensor {} [ Sens.actuatorvel { name: "se_avel", actuator: "a1" } ]
+
+      it "actuatorfrc" $ parseOk $ m $
+        X.sensor {} [ Sens.actuatorfrc { name: "se_afrc", actuator: "a1" } ]
+
+    describe "frame-based" do
+      it "framepos" $ parseOk $ m $
+        X.sensor {} [ Sens.framepos { name: "se_fpos", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "framequat" $ parseOk $ m $
+        X.sensor {} [ Sens.framequat { name: "se_fquat", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "framexaxis" $ parseOk $ m $
+        X.sensor {} [ Sens.framexaxis { name: "se_fxax", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "frameyaxis" $ parseOk $ m $
+        X.sensor {} [ Sens.frameyaxis { name: "se_fyax", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "framezaxis" $ parseOk $ m $
+        X.sensor {} [ Sens.framezaxis { name: "se_fzax", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "framelinvel" $ parseOk $ m $
+        X.sensor {} [ Sens.framelinvel { name: "se_flv", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "frameangvel" $ parseOk $ m $
+        X.sensor {} [ Sens.frameangvel { name: "se_fav", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "framelinvel with ref" $ parseOk $ m $
+        X.sensor {} [ Sens.framelinvel { name: "se_flvr", objtype: X.kw X.Body, objname: "b1", reftype: X.kw X.Body, refname: "b2" } ]
+
+      it "framelinacc" $ parseOk $ m $
+        X.sensor {} [ Sens.framelinacc { name: "se_fla", objtype: X.kw X.Body, objname: "b1" } ]
+
+      it "frameangacc" $ parseOk $ m $
+        X.sensor {} [ Sens.frameangacc { name: "se_faa", objtype: X.kw X.Body, objname: "b1" } ]
+
+    describe "subtree" do
+      it "subtreecom" $ parseOk $ m $
+        X.sensor {} [ Sens.subtreecom { name: "se_stcom", body: "b1" } ]
+
+      it "subtreelinvel" $ parseOk $ m $
+        X.sensor {} [ Sens.subtreelinvel { name: "se_stlv", body: "b1" } ]
+
+      it "subtreeangmom" $ parseOk $ m $
+        X.sensor {} [ Sens.subtreeangmom { name: "se_stam", body: "b1" } ]
+
+    describe "collision" do
+      it "distance" $ parseOk $ m $
+        X.sensor {} [ Sens.distance { name: "se_dist", geom1: "g1", geom2: "g2" } ]
+
+      it "normal" $ parseOk $ m $
+        X.sensor {} [ Sens.normal { name: "se_norm", geom1: "g1", geom2: "g2" } ]
+
+      it "fromto" $ parseOk $ m $
+        X.sensor {} [ Sens.fromto { name: "se_ft", geom1: "g1", geom2: "g2" } ]
+
+      it "contact" $ parseOk $ m $
+        X.sensor {} [ Sens.contact { name: "se_cont", body1: "b1", body2: "b2" } ]
+
+    describe "other" do
+      it "insidesite" $ parseOk $ m $
+        X.sensor {} [ Sens.insidesite { name: "se_inside", objtype: X.kw X.Geom, objname: "g1", site: "s1" } ]
+
+      it "e_potential" $ parseOk $ m $
+        X.sensor {} [ Sens.e_potential { name: "se_ep" } ]
+
+      it "e_kinetic" $ parseOk $ m $
+        X.sensor {} [ Sens.e_kinetic { name: "se_ek" } ]
+
+      it "clock" $ parseOk $ m $
+        X.sensor {} [ Sens.clock { name: "se_clock" } ]
+
+      it "user" $ parseOk $ m $
+        X.sensor {} [ Sens.user { name: "se_user", objtype: "body", objname: "b1", datatype: X.kw X.Real, needstage: X.kw X.Vel, dim: 1 } ]
+
+    describe "common props" do
+      it "noise + cutoff" $ parseOk $ m $
+        X.sensor {} [ Sens.touch { name: "se_noisy", site: "s1", noise: 0.01, cutoff: 100.0 } ]
diff --git a/test/Mujoco.MJCF.Tendon.purs b/test/Mujoco.MJCF.Tendon.purs
new file mode 100644
index 0000000..39d8bd8
--- /dev/null
+++ b/test/Mujoco.MJCF.Tendon.purs
@@ -0,0 +1,64 @@
+module Test.Mujoco.MJCF.Tendon where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Tendon as Tendon
+import Mujoco.MJCF.XML (Node)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+-- | Model with two bodies, two hinge joints, and two sites for tendon routing
+m :: Node -> Node
+m t = X.mujoco {}
+  [ X.compiler { inertiafromgeom: X.true_ }
+  , X.worldbody {}
+      [ X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
+          [ X.joint { name: "j1", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+          , X.geom { type: X.kw X.Capsule, size: [0.05, 0.2] } unit
+          , X.site { name: "s1", pos: 0.0 /\ 0.0 /\ 0.2, size: 0.01 /\ 0.01 /\ 0.01 }
+          , X.body { name: "b2", pos: 0.0 /\ 0.0 /\ 0.5 }
+              [ X.joint { name: "j2", type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
+              , X.geom { type: X.kw X.Capsule, size: [0.05, 0.2] } unit
+              , X.site { name: "s2", pos: 0.0 /\ 0.0 /\ 0.2, size: 0.01 /\ 0.01 /\ 0.01 }
+              ]
+          ]
+      ]
+  , t
+  ]
+
+spec :: MjcfSpec Unit
+spec =
+  describe "tendon" do
+    describe "spatial" do
+      it "basic site routing" $ parseOk $ m $ Tendon.tendon {} $
+        Tendon.spatial { name: "t_spatial" }
+          [ Tendon.site { site: "s1" }
+          , Tendon.site { site: "s2" }
+          ]
+
+      it "with pulley" $ parseOk $ m $ Tendon.tendon {} $
+        Tendon.spatial { name: "t_pulley" }
+          [ Tendon.site { site: "s1" }
+          , Tendon.pulley { divisor: 2.0 }
+          , Tendon.site { site: "s2" }
+          ]
+
+      it "limited + range + stiffness + damping" $ parseOk $ m $ Tendon.tendon {} $
+        Tendon.spatial { name: "t_props", limited: X.true_, range: (-1.0) /\ 1.0, stiffness: 100.0, damping: 10.0 }
+          [ Tendon.site { site: "s1" }
+          , Tendon.site { site: "s2" }
+          ]
+
+    describe "fixed" do
+      it "basic joint" $ parseOk $ m $ Tendon.tendon {} $
+        Tendon.fixed { name: "t_fixed" }
+          [ Tendon.joint { joint: "j1", coef: 1.0 }
+          , Tendon.joint { joint: "j2", coef: -1.0 }
+          ]
+
+      it "stiffness + damping" $ parseOk $ m $ Tendon.tendon {} $
+        Tendon.fixed { name: "t_fixed2", stiffness: 50.0, damping: 5.0 }
+          [ Tendon.joint { joint: "j1", coef: 1.0 }
+          ]
diff --git a/test/Mujoco.MJCF.Visual.purs b/test/Mujoco.MJCF.Visual.purs
new file mode 100644
index 0000000..7c6b0dd
--- /dev/null
+++ b/test/Mujoco.MJCF.Visual.purs
@@ -0,0 +1,82 @@
+module Test.Mujoco.MJCF.Visual where
+
+import Prelude
+
+import Data.Tuple.Nested ((/\))
+import Mujoco.MJCF as X
+import Mujoco.MJCF.Visual as Vis
+import Mujoco.MJCF.XML (Node)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseOk)
+import Test.Spec (describe, it)
+
+v :: Node -> Node
+v c = X.mujoco {}
+  [ Vis.visual {} [ c ]
+  , X.worldbody {} unit
+  ]
+
+spec :: MjcfSpec Unit
+spec =
+  describe "visual" do
+    describe "global" do
+      it "fovy + linewidth" $ parseOk $ v $
+        Vis.global { fovy: 45.0, linewidth: 2.0 }
+
+      it "offwidth + offheight" $ parseOk $ v $
+        Vis.global { offwidth: 1920, offheight: 1080 }
+
+      it "orthographic + ellipsoidinertia" $ parseOk $ v $
+        Vis.global { orthographic: true, ellipsoidinertia: true }
+
+    describe "quality" do
+      it "shadowsize + offsamples" $ parseOk $ v $
+        Vis.quality { shadowsize: 4096, offsamples: 8 }
+
+      it "numslices + numstacks + numquads" $ parseOk $ v $
+        Vis.quality { numslices: 32, numstacks: 32, numquads: 4 }
+
+    describe "headlight" do
+      it "ambient + diffuse + specular" $ parseOk $ v $
+        Vis.headlight { ambient: 0.3 /\ 0.3 /\ 0.3, diffuse: 0.6 /\ 0.6 /\ 0.6, specular: 0.2 /\ 0.2 /\ 0.2 }
+
+      it "active" $ parseOk $ v $
+        Vis.headlight { active: 0 }
+
+    describe "map" do
+      it "stiffness + force + torque" $ parseOk $ v $
+        Vis.map { stiffness: 100.0, force: 0.05, torque: 0.1 }
+
+      it "fogstart + fogend" $ parseOk $ v $
+        Vis.map { fogstart: 2.0, fogend: 10.0 }
+
+      it "znear + zfar" $ parseOk $ v $
+        Vis.map { znear: 0.01, zfar: 50.0 }
+
+      it "shadowclip + shadowscale" $ parseOk $ v $
+        Vis.map { shadowclip: 0.5, shadowscale: 0.5 }
+
+    describe "scale" do
+      it "forcewidth + contactwidth + contactheight" $ parseOk $ v $
+        Vis.scale { forcewidth: 0.1, contactwidth: 0.3, contactheight: 0.1 }
+
+      it "jointlength + jointwidth" $ parseOk $ v $
+        Vis.scale { jointlength: 0.5, jointwidth: 0.1 }
+
+      it "framelength + framewidth" $ parseOk $ v $
+        Vis.scale { framelength: 1.0, framewidth: 0.05 }
+
+      it "actuatorlength + actuatorwidth" $ parseOk $ v $
+        Vis.scale { actuatorlength: 0.7, actuatorwidth: 0.1 }
+
+    describe "rgba" do
+      it "fog + haze" $ parseOk $ v $
+        Vis.rgba { fog: 0.0 /\ 0.0 /\ 0.0 /\ 1.0, haze: 1.0 /\ 1.0 /\ 1.0 /\ 1.0 }
+
+      it "force + inertia + joint" $ parseOk $ v $
+        Vis.rgba { force: 1.0 /\ 0.5 /\ 0.5 /\ 1.0, inertia: 0.8 /\ 0.2 /\ 0.2 /\ 0.6, joint: 0.2 /\ 0.6 /\ 0.8 /\ 1.0 }
+
+      it "com + camera + light" $ parseOk $ v $
+        Vis.rgba { com: 0.0 /\ 1.0 /\ 0.0 /\ 1.0, camera: 0.6 /\ 0.9 /\ 0.6 /\ 1.0, light: 0.9 /\ 0.9 /\ 0.3 /\ 1.0 }
+
+      it "contact colors" $ parseOk $ v $
+        Vis.rgba { contactpoint: 0.9 /\ 0.2 /\ 0.2 /\ 1.0, contactforce: 0.2 /\ 0.9 /\ 0.2 /\ 1.0, contactfriction: 0.2 /\ 0.2 /\ 0.9 /\ 1.0, contacttorque: 0.9 /\ 0.9 /\ 0.2 /\ 1.0 }
diff --git a/test/Mujoco.MJCF.XML.Prop.purs b/test/Mujoco.MJCF.XML.Prop.purs
index 1829d2d..a99fb97 100644
--- a/test/Mujoco.MJCF.XML.Prop.purs
+++ b/test/Mujoco.MJCF.XML.Prop.purs
@@ -6,7 +6,8 @@ import Data.Tuple.Nested (type (/\), (/\))
 import Mujoco.MJCF.XML.Prop (class SerializeProps', serialize, serializeProps)
 import Prim.Row (class Union)
 import Prim.RowList (class RowToList)
-import Test.Spec (Spec, describe, it)
+import Test.Mujoco.MJCF.Util (MjcfSpec)
+import Test.Spec (describe, it)
 import Test.Spec.Assertions (shouldEqual)
 import Unsafe.Coerce (unsafeCoerce)
 
@@ -20,7 +21,7 @@ type Props =
   , bool :: Boolean
   )
 
-spec :: Spec Unit
+spec :: MjcfSpec Unit
 spec =
   describe "Mujoco.MJCF.XML.Prop" do
     describe "Serialize" do
diff --git a/test/Mujoco.MJCF.purs b/test/Mujoco.MJCF.purs
index e9fb73b..e801bdf 100644
--- a/test/Mujoco.MJCF.purs
+++ b/test/Mujoco.MJCF.purs
@@ -2,111 +2,94 @@ module Test.Mujoco.MJCF where
 
 import Prelude
 
-import Control.Monad.Error.Class (try)
-import Data.Either (isLeft)
 import Data.Tuple.Nested ((/\))
-import Effect.Aff (Aff)
-import Effect.Class (liftEffect)
 import Mujoco.MJCF as X
-import Mujoco.MJCF.Geom as X.G
-import Mujoco.Wasm (renderSpec)
-import Mujoco.MJCF.XML (Node)
-import Mujoco.MJCF.XML as XML
-import Test.Assert (assertTrue)
-import Test.Spec (Spec, describe, it)
+import Test.Mujoco.MJCF.Util (MjcfSpec, parseFail, parseOk, w)
+import Test.Spec (describe, it)
 
-ok :: Node -> Aff Unit
-ok = void <<< renderSpec
-
-fail :: Node -> Aff Unit
-fail = (liftEffect <<< assertTrue <<< isLeft) <=< (try <<< renderSpec)
-
-w :: forall a. XML.Children a => a -> Node
-w = X.mujoco {} <<< X.worldbody {}
-
-spec :: Spec Unit
+spec :: MjcfSpec Unit
 spec =
   describe "MJCF" do
-    it "</>" $ fail $ X.empty
-    it "<mujoco>" $ ok $ X.mujoco {} unit
-    it "<worldbody>" $ ok $ X.mujoco {} $ X.worldbody {} unit
+    it "</>" $ parseFail $ X.empty
+    it "<mujoco>" $ parseOk $ X.mujoco {} unit
+    it "<worldbody>" $ parseOk $ X.mujoco {} $ X.worldbody {} unit
 
     describe "compiler" do
-      it "empty" $ ok $ X.mujoco {}
+      it "empty" $ parseOk $ X.mujoco {}
         [ X.compiler {}
         , X.worldbody {} unit
         ]
 
-      it "angle=radian" $ ok $ X.mujoco {}
+      it "angle=radian" $ parseOk $ X.mujoco {}
         [ X.compiler { angle: X.kw X.Radian }
         , X.worldbody {} unit
         ]
 
-      it "autolimits + coordinate" $ ok $ X.mujoco {}
+      it "autolimits + coordinate" $ parseOk $ X.mujoco {}
         [ X.compiler { autolimits: true, coordinate: X.kw X.Local }
         , X.worldbody {} unit
         ]
 
-      it "inertiafromgeom=auto" $ ok $ X.mujoco {}
+      it "inertiafromgeom=auto" $ parseOk $ X.mujoco {}
         [ X.compiler { inertiafromgeom: X.kw X.Auto }
         , X.worldbody {} unit
         ]
 
-      it "boundmass + boundinertia" $ ok $ X.mujoco {}
+      it "boundmass + boundinertia" $ parseOk $ X.mujoco {}
         [ X.compiler { boundmass: 0.01, boundinertia: 0.001 }
         , X.worldbody {} unit
         ]
 
     describe "size" do
-      it "empty" $ ok $ X.mujoco {}
+      it "empty" $ parseOk $ X.mujoco {}
         [ X.size {}
         , X.worldbody {} unit
         ]
 
-      it "memory" $ ok $ X.mujoco {}
+      it "memory" $ parseOk $ X.mujoco {}
         [ X.size { memory: "16M" }
         , X.worldbody {} unit
         ]
 
-      it "nuser fields" $ ok $ X.mujoco {}
+      it "nuser fields" $ parseOk $ X.mujoco {}
         [ X.size { nuser_body: 2, nuser_jnt: 1, nuser_geom: 3 }
         , X.worldbody {} unit
         ]
 
     describe "option" do
-      it "timestep + integrator" $ ok $ X.mujoco {}
+      it "timestep + integrator" $ parseOk $ X.mujoco {}
         [ X.option { timestep: 0.001, integrator: X.kw X.RK4 } unit
         , X.worldbody {} unit
         ]
 
-      it "gravity + solver" $ ok $ X.mujoco {}
+      it "gravity + solver" $ parseOk $ X.mujoco {}
         [ X.option { gravity: 0.0 /\ 0.0 /\ (-9.81), solver: X.kw X.Newton } unit
         , X.worldbody {} unit
         ]
 
     describe "statistic" do
-      it "extent + center" $ ok $ X.mujoco {}
+      it "extent + center" $ parseOk $ X.mujoco {}
         [ X.statistic { extent: 2.0, center: 0.0 /\ 0.0 /\ 1.0 }
         , X.worldbody {} unit
         ]
 
     describe "asset" do
       describe "mesh" do
-        it "inline vertex" $ ok $ X.mujoco {}
+        it "inline vertex" $ parseOk $ X.mujoco {}
           [ X.asset {}
               [ X.mesh { name: "tetra", vertex: [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0] } unit ]
           , X.worldbody {} unit
           ]
 
       describe "hfield" do
-        it "nrow + ncol + size" $ ok $ X.mujoco {}
+        it "nrow + ncol + size" $ parseOk $ X.mujoco {}
           [ X.asset {}
               [ X.hfield { name: "terrain", nrow: 10, ncol: 10, size: 1.0 /\ 1.0 /\ 0.5 /\ 0.1 } ]
           , X.worldbody {} unit
           ]
 
       describe "texture" do
-        it "procedural checker" $ ok $ X.mujoco {}
+        it "procedural checker" $ parseOk $ X.mujoco {}
           [ X.asset {}
               [ X.texture
                   { name: "grid"
@@ -122,7 +105,7 @@ spec =
           ]
 
       describe "material" do
-        it "rgba + specular" $ ok $ X.mujoco {}
+        it "rgba + specular" $ parseOk $ X.mujoco {}
           [ X.asset {}
               [ X.material { name: "mat1", rgba: 0.8 /\ 0.2 /\ 0.2 /\ 1.0, specular: 0.8 } unit ]
           , X.worldbody {} unit
@@ -130,77 +113,77 @@ spec =
 
     describe "body" do
       describe "joint" do
-        it "hinge" $ ok $ w $
+        it "hinge" $ parseOk $ w $
           X.body { name: "b1", pos: 0.0 /\ 0.0 /\ 0.5 }
             [ X.joint { type: X.kw X.Hinge, axis: 1.0 /\ 0.0 /\ 0.0 }
             , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
             ]
 
-        it "slide with range" $ ok $ w $
+        it "slide with range" $ parseOk $ w $
           X.body { name: "slider", pos: 0.0 /\ 0.0 /\ 1.0 }
             [ X.joint { type: X.kw X.Slide, axis: 0.0 /\ 0.0 /\ 1.0, range: (-1.0) /\ 1.0, limited: X.true_ }
             , X.geom { type: X.kw X.Box, size: [0.1, 0.1, 0.1] } unit
             ]
 
-        it "stiffness + damping" $ ok $ w $
+        it "stiffness + damping" $ parseOk $ w $
           X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
             [ X.joint { type: X.kw X.Hinge, stiffness: 100.0, damping: 10.0, armature: 0.1 }
             , X.geom { type: X.kw X.Sphere, size: [0.05, 0.0, 0.0] } unit
             ]
 
       describe "freejoint" do
-        it "basic" $ ok $ w $
+        it "basic" $ parseOk $ w $
           X.body { name: "free_body", pos: 0.0 /\ 0.0 /\ 1.0 }
             [ X.freejoint { name: "fj" }
             , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
             ]
 
       describe "geom" do
-        it "sphere" $ ok $ w $
+        it "sphere" $ parseOk $ w $
           X.geom { type: X.kw X.Sphere, size: [1.0, 0.0, 0.0] } unit
 
-        it "capsule fromto" $ ok $ w $
+        it "capsule fromto" $ parseOk $ w $
           X.geom { type: X.kw X.Capsule, fromto: [0.0, 0.0, 0.0, 0.0, 0.0, 1.0], size: [0.05, 0.0, 0.0] } unit
 
-        it "box with material" $ ok $ X.mujoco {}
+        it "box with material" $ parseOk $ X.mujoco {}
           [ X.asset {}
               [ X.material { name: "red", rgba: 1.0 /\ 0.0 /\ 0.0 /\ 1.0 } unit ]
           , X.worldbody {} $
               X.geom { type: X.kw X.Box, size: [0.5, 0.5, 0.5], material: "red" } unit
           ]
 
-        it "plane" $ ok $ w $
+        it "plane" $ parseOk $ w $
           X.geom { type: X.kw X.Plane, size: [5.0, 5.0, 0.1] } unit
 
-        it "friction + density" $ ok $ w $
+        it "friction + density" $ parseOk $ w $
           X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0], friction: 0.5 /\ 0.005 /\ 0.0001, density: 500.0 } unit
 
       describe "site" do
-        it "basic" $ ok $ w $
+        it "basic" $ parseOk $ w $
           X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
             [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
             , X.site { name: "s1", pos: 0.0 /\ 0.0 /\ 0.1, size: 0.01 /\ 0.01 /\ 0.01 }
             ]
 
       describe "camera" do
-        it "fixed" $ ok $ w $
+        it "fixed" $ parseOk $ w $
           X.camera { name: "cam1", pos: 0.0 /\ (-2.0) /\ 1.0, fovy: 60.0 }
 
-        it "tracking" $ ok $ w $
+        it "tracking" $ parseOk $ w $
           X.body { name: "target_body", pos: 0.0 /\ 0.0 /\ 0.5 }
             [ X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
             , X.camera { name: "tracker", mode: X.kw X.Targetbody, target: "target_body", pos: 1.0 /\ 0.0 /\ 0.5 }
             ]
 
       describe "light" do
-        it "spotlight" $ ok $ w $
+        it "spotlight" $ parseOk $ w $
           X.light { name: "spot1", pos: 0.0 /\ 0.0 /\ 3.0, dir: 0.0 /\ 0.0 /\ (-1.0), diffuse: 1.0 /\ 1.0 /\ 1.0 }
 
-        it "directional" $ ok $ w $
+        it "directional" $ parseOk $ w $
           X.light { name: "sun", type: X.kw X.Directional, dir: 0.0 /\ (-1.0) /\ (-1.0), castshadow: true }
 
       describe "inertial" do
-        it "explicit mass + diaginertia" $ ok $ w $
+        it "explicit mass + diaginertia" $ parseOk $ w $
           X.body { pos: 0.0 /\ 0.0 /\ 0.0 }
             [ X.inertial { pos: 0.0 /\ 0.0 /\ 0.0, mass: 1.0, diaginertia: 0.01 /\ 0.01 /\ 0.01 }
             , X.geom { type: X.kw X.Sphere, size: [0.1, 0.0, 0.0] } unit
@@ -208,7 +191,7 @@ spec =
 
     describe "composite" do
       it "full model"
-        $ ok
+        $ parseOk
         $ X.mujoco { model: "test" }
             [ X.compiler { angle: X.kw X.Radian, inertiafromgeom: X.true_ }
             , X.option { timestep: 0.002, gravity: 0.0 /\ 0.0 /\ (-9.81) }
@@ -227,7 +210,7 @@ spec =
                 ]
             ]
 
-      it "bodies with joints" $ ok $ w
+      it "bodies with joints" $ parseOk $ w
         [ X.light { name: "top", pos: 0.0 /\ 0.0 /\ 1.0 }
         , X.body {}
           [ X.joint { name: "v0_rx", damping: 1.0, stiffness: 10.0, axis: 1.0 /\ 0.0 /\ 0.0, pos: 0.0 /\ 0.0 /\ (-0.5) }
diff --git a/test/Mujoco.Wasm.purs b/test/Mujoco.Wasm.purs
index f6c6615..aeaf7b5 100644
--- a/test/Mujoco.Wasm.purs
+++ b/test/Mujoco.Wasm.purs
@@ -1,21 +1,10 @@
 module Mujoco.Wasm where
 
-import Prelude
-
 import Control.Promise (Promise)
-import Control.Promise as Promise
 import Effect (Effect)
-import Effect.Aff (Aff)
-import Effect.Class (liftEffect)
-import Mujoco.MJCF.XML as XML
 
 foreign import data Mujoco :: Type
 foreign import data Spec :: Type
 
 foreign import loadMujoco :: Effect (Promise Mujoco)
 foreign import parseXMLString :: Mujoco -> String -> Effect Spec
-
-renderSpec :: XML.Node -> Aff Spec
-renderSpec node = do
-  mj <- Promise.toAffE loadMujoco
-  liftEffect $ parseXMLString mj $ XML.render node
diff --git a/test/Mujuco.MJCF.Util.purs b/test/Mujuco.MJCF.Util.purs
new file mode 100644
index 0000000..390729a
--- /dev/null
+++ b/test/Mujuco.MJCF.Util.purs
@@ -0,0 +1,59 @@
+module Test.Mujoco.MJCF.Util where
+
+import Prelude
+
+import Control.Monad.Error.Class (class MonadError, class MonadThrow, try)
+import Control.Monad.Reader (class MonadAsk, class MonadReader, ReaderT, ask, runReaderT)
+import Control.Promise as Promise
+import Data.Either (isLeft)
+import Data.Identity (Identity)
+import Data.Newtype (class Newtype, unwrap)
+import Effect.Aff (Aff)
+import Effect.Aff.Class (class MonadAff, liftAff)
+import Effect.Class (class MonadEffect, liftEffect)
+import Effect.Exception (Error)
+import Mujoco.MJCF as X
+import Mujoco.MJCF.XML (Node)
+import Mujoco.MJCF.XML as XML
+import Mujoco.Wasm (Mujoco)
+import Mujoco.Wasm as Mj
+import Test.Assert (assertTrue)
+import Test.Spec (SpecT, Spec, hoistSpec)
+
+newtype T a = T (ReaderT Mujoco Aff a)
+derive instance Newtype (T a) _
+derive newtype instance Functor T
+derive newtype instance Applicative T
+derive newtype instance Apply T
+derive newtype instance Bind T
+derive newtype instance Monad T
+derive newtype instance MonadReader Mujoco T
+derive newtype instance MonadAsk Mujoco T
+derive newtype instance MonadEffect T
+derive newtype instance MonadAff T
+derive newtype instance MonadThrow Error T
+derive newtype instance MonadError Error T
+
+type MjcfSpec a = SpecT T Unit Identity a
+
+mjcf :: forall a. MjcfSpec a -> Spec a
+mjcf = hoistSpec identity (\_ -> runT)
+
+runT :: forall a. T a -> Aff a
+runT m = do
+  mj <- liftAff $ Promise.toAffE Mj.loadMujoco
+  runReaderT (unwrap m) mj
+
+renderSpec :: XML.Node -> T Mj.Spec
+renderSpec node = do
+  mj <- ask
+  liftEffect $ Mj.parseXMLString mj $ XML.render node
+
+parseOk :: XML.Node -> T Unit
+parseOk = void <<< renderSpec
+
+parseFail :: XML.Node -> T Unit
+parseFail = (liftEffect <<< assertTrue <<< isLeft) <=< (try <<< renderSpec)
+
+w :: forall a. XML.Children a => a -> Node
+w = X.mujoco {} <<< X.worldbody {}