diff --git a/src/effects/components.rs b/src/effects/components.rs
index 8fda8ac..2d407a0 100644
--- a/src/effects/components.rs
+++ b/src/effects/components.rs
@@ -120,12 +120,10 @@ mod tests {
     use proptest_derive::Arbitrary;
 
     use super::*;
+    use crate::effects::number_data::NumberComponent;
     use crate::effects::one_way_fn::OneWayFn;
     use crate::system_combinators::affect;
 
-    #[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Component, Arbitrary)]
-    struct NumberComponent<const MARKER: usize>(u128);
-
     #[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Component)]
     struct MarkerComponent;
 
diff --git a/src/effects/event.rs b/src/effects/event.rs
index d2039f1..16c99ef 100644
--- a/src/effects/event.rs
+++ b/src/effects/event.rs
@@ -22,14 +22,11 @@ where
 #[cfg(test)]
 mod tests {
     use proptest::prelude::*;
-    use proptest_derive::Arbitrary;
 
     use super::*;
+    use crate::effects::number_data::NumberEvent;
     use crate::prelude::affect;
 
-    #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Event, Arbitrary)]
-    struct NumberEvent(u128);
-
     proptest! {
         #[test]
         fn event_send_produces_events(events in prop::collection::vec(any::<NumberEvent>(), 1..10)) {
diff --git a/src/effects/mod.rs b/src/effects/mod.rs
index 8bc5ff5..282698f 100644
--- a/src/effects/mod.rs
+++ b/src/effects/mod.rs
@@ -13,3 +13,6 @@ pub use components::{ComponentsPut, ComponentsWith};
 
 #[cfg(test)]
 mod one_way_fn;
+
+#[cfg(test)]
+mod number_data;
diff --git a/src/effects/number_data.rs b/src/effects/number_data.rs
new file mode 100644
index 0000000..fba8d69
--- /dev/null
+++ b/src/effects/number_data.rs
@@ -0,0 +1,18 @@
+//! Test types for various `bevy` data classes, all storing numbers, all proptest-generatable.
+use bevy::prelude::*;
+use proptest_derive::Arbitrary;
+
+/// Test `Component` storing a number.
+///
+/// The const generic MARKER can be used to easily define as many component types as you need.
+/// i.e., `Numbercomponent<0>` and `NumberComponent<1>` are different components in `bevy`.
+#[derive(Copy, Clone, Default, Debug, PartialEq, Eq, Component, Arbitrary)]
+pub struct NumberComponent<const MARKER: usize>(pub u128);
+
+/// Test `Event` storing a number.
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, Event, Arbitrary)]
+pub struct NumberEvent(pub u128);
+
+/// Test `Resource` storing a number.
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Resource, Arbitrary)]
+pub struct NumberResource(pub u128);
diff --git a/src/effects/resource.rs b/src/effects/resource.rs
index 6372450..59d9e08 100644
--- a/src/effects/resource.rs
+++ b/src/effects/resource.rs
@@ -62,15 +62,12 @@ where
 #[cfg(test)]
 mod tests {
     use proptest::prelude::*;
-    use proptest_derive::Arbitrary;
 
     use super::*;
+    use crate::effects::number_data::NumberResource;
     use crate::effects::one_way_fn::OneWayFn;
     use crate::system_combinators::affect;
 
-    #[derive(Copy, Clone, Debug, PartialEq, Eq, Resource, Arbitrary)]
-    struct NumberResource(u128);
-
     proptest! {
         #[test]
         fn res_put_overwrites_initial_state(initial: NumberResource, put: NumberResource) {