# Objective
```
cargo test --package bevy_ecs --lib --all-features
```
fails to compile, with output like
> error[E0433]: failed to resolve: could not find `Serialize` in `serde`
> --> crates/bevy_ecs/src/entity/index_set.rs:14:69
> |
> 14 | #[cfg_attr(feature = "serialize", derive(serde::Deserialize,
serde::Serialize))]
> | ^^^^^^^^^ could not find `Serialize` in `serde`
> |
> note: found an item that was configured out
> -->
/home/alice/.cargo/registry/src/index.crates.io-6f17d22bba15001f/serde-1.0.217/src/lib.rs:343:37
> |
> 343 | pub use serde_derive::{Deserialize, Serialize};
> | ^^^^^^^^^
> note: the item is gated behind the `serde_derive` feature
> -->
/home/alice/.cargo/registry/src/index.crates.io-6f17d22bba15001f/serde-1.0.217/src/lib.rs:341:7
> |
> 341 | #[cfg(feature = "serde_derive")]
> | ^^^^^^^^^^^^^^^^^^^^^^^^
## Solution
Add the required feature flags and get bevy_ecs compiling standalone
corrctly.
## Testing
The command above now compiles succesfully. Note that several system
stepping tests are failing, and were not being tested in CI. That's a
different PR's problem though.
da5064889a