diff --git a/Cargo.lock b/Cargo.lock
index d3bc293..043962e 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -346,6 +346,7 @@ name = "coremem_cross"
 version = "0.2.0"
 dependencies = [
  "coremem_cross",
+ "float_eq",
  "serde",
 ]
 
diff --git a/crates/coremem/Cargo.toml b/crates/coremem/Cargo.toml
index 91a019d..d8c0542 100644
--- a/crates/coremem/Cargo.toml
+++ b/crates/coremem/Cargo.toml
@@ -17,7 +17,6 @@ crossterm = "0.24"  # MIT
 csv = "1.1"  # MIT or Unlicense
 dashmap = "5.3"  # MIT
 env_logger = "0.9"  # MIT or Apache 2.0
-float_eq = "1.0"  # MIT or Apache 2.0
 font8x8 = "0.3"  # MIT
 futures = "0.3"  # MIT or Apache 2.0
 image = "0.24"  # MIT
@@ -48,6 +47,7 @@ coremem_cross = { path = "../cross", features = ["iter", "fmt", "serde", "std"]
 
 [dev-dependencies]
 criterion = "0.3"
+float_eq = "1.0"  # MIT or Apache 2.0
 
 [[bench]]
 name = "driver"
diff --git a/crates/cross/Cargo.toml b/crates/cross/Cargo.toml
index 8bd65f0..f4dde1a 100644
--- a/crates/cross/Cargo.toml
+++ b/crates/cross/Cargo.toml
@@ -13,5 +13,7 @@ std = []
 
 [dependencies]
 serde = { version = "1.0", optional = true }  # MIT or Apache 2.0
+
 [dev-dependencies]
 coremem_cross = { path = ".", default-features = false, features = ["iter", "fmt", "std"] }
+float_eq = "1.0"  # MIT or Apache 2.0
diff --git a/crates/cross/src/vec.rs b/crates/cross/src/vec.rs
index fbdbcb6..2ac670f 100644
--- a/crates/cross/src/vec.rs
+++ b/crates/cross/src/vec.rs
@@ -144,7 +144,6 @@ impl<R: Real> Vec2<R> {
     //     self.y.to_f64().atan2(self.x.to_f64()).cast()
     // }
 
-    // TODO test
     pub fn rotate(&self, angle: R) -> Self {
         let (sin, cos) = angle.sin_cos();
         let map_1x_0y = Vec2::new(cos, sin);
@@ -492,3 +491,41 @@ impl<R: Real + fmt::Display> fmt::Display for Vec3<R> {
         fmt::Display::fmt(")", f)
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use float_eq::assert_float_eq;
+
+    fn assert_vec2(got: Vec2<f32>, want: Vec2<f32>) {
+        assert_float_eq!(got.x(), want.x(), abs <= 1e-6);
+        assert_float_eq!(got.y(), want.y(), abs <= 1e-6);
+    }
+    #[test]
+    fn vec2_rotate_trivial() {
+        // no-op rotate
+        assert_vec2(Vec2::new(1.0, 0.0).rotate(0.0), Vec2::new(1.0, 0.0));
+        assert_vec2(Vec2::new(1.0, 1.0).rotate(f32::two_pi()), Vec2::new(1.0, 1.0));
+        assert_vec2(Vec2::new(-2.0, 3.0).rotate(-f32::two_pi()), Vec2::new(-2.0, 3.0));
+    }
+
+    #[test]
+    fn vec2_rotate_quarter_turns() {
+        assert_vec2(Vec2::new(1.0, 0.0).rotate(f32::pi()), Vec2::new(-1.0, 0.0));
+        assert_vec2(Vec2::new(1.0, -1.0).rotate(f32::pi()), Vec2::new(-1.0, 1.0));
+
+        assert_vec2(Vec2::new(1.0, 0.0).rotate(0.5*f32::pi()), Vec2::new(0.0, 1.0));
+        assert_vec2(Vec2::new(1.0, -1.0).rotate(0.5*f32::pi()), Vec2::new(1.0, 1.0));
+
+        assert_vec2(Vec2::new(-1.0, 0.0).rotate(-0.5*f32::pi()), Vec2::new(0.0, 1.0));
+        assert_vec2(Vec2::new(-1.0, -1.0).rotate(-0.5*f32::pi()), Vec2::new(-1.0, 1.0));
+    }
+
+    #[test]
+    fn vec2_rotate_zero() {
+        assert_vec2(Vec2::new(0.0, 0.0).rotate(1.0), Vec2::new(0.0, 0.0));
+        assert_vec2(Vec2::new(0.0, 0.0).rotate(1e9), Vec2::new(0.0, 0.0));
+    }
+
+    // TODO: lots more Vec, Vec2 tests need backfilling
+}