[Penpal] fix genesis presets - assign proper ED to accounts (#11575)

Penpal had values below the ED for initializing asset balances for some
accounts. This has not been detected as no unit tests actually use the
presets. This PR fixes the invalid values, and it also adds some unit
tests for validating that the presets build at least.

Closes #11558.

---------

Co-authored-by: clangenb <clangenb@users.noreply.github.com>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: clangenb

Cargo.lock

@@ -90,6 +90,9 @@ primitive-types = { workspace = true, default-features = false, features = [
 	"scale-info",
 ] }
 
+[dev-dependencies]
+sp-io = { workspace = true, default-features = true }
+
 [build-dependencies]
 substrate-wasm-builder = { optional = true, workspace = true, default-features = true }
 

cumulus/parachains/runtimes/testing/penpal/Cargo.toml

@@ -81,8 +81,8 @@ fn penpal_parachain_genesis(
 			assets: vec![
 				(RelayLocation::get(), sudo.clone(), true, EXISTENTIAL_DEPOSIT),
 				(LocalPen2Asset::get(), sudo.clone(), false, EXISTENTIAL_DEPOSIT),
-				(UsdtFromAssetHub::get(), sudo.clone(), true, EXISTENTIAL_DEPOSIT),
-				(EthFromEthereum::get(), sudo.clone(), true, EXISTENTIAL_DEPOSIT),
+				(UsdtFromAssetHub::get(), sudo.clone(), true, USDT_ED),
+				(EthFromEthereum::get(), sudo.clone(), true, ETHER_MIN_BALANCE),
 			],
 			metadata: vec![
 				(
@@ -165,3 +165,44 @@ pub fn preset_names() -> Vec<PresetId> {
 pub fn penpal_session_keys(keys: AuraId) -> crate::SessionKeys {
 	crate::SessionKeys { aura: keys }
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	// Duplicated from `sc_chain_spec::json_patch::merge` which lives in a node-side crate
+	// with heavy transitive deps (sc-executor, sc-network, etc.), making it unsuitable as a
+	// dev-dependency for a runtime crate.
+	fn merge(base: &mut serde_json::Value, patch: serde_json::Value) {
+		match (base, patch) {
+			(serde_json::Value::Object(base), serde_json::Value::Object(patch)) => {
+				for (k, v) in patch {
+					merge(base.entry(k).or_insert(serde_json::Value::Null), v);
+				}
+			},
+			(base, patch) => *base = patch,
+		}
+	}
+
+	fn assert_genesis_preset_valid(preset_id: &sp_genesis_builder::PresetId) {
+		let patch: serde_json::Value =
+			serde_json::from_slice(&get_preset(preset_id).expect("preset exists")).unwrap();
+		let mut config = serde_json::to_value(RuntimeGenesisConfig::default()).unwrap();
+		merge(&mut config, patch);
+		let json = serde_json::to_vec(&config).unwrap();
+		sp_io::TestExternalities::default().execute_with(|| {
+			frame_support::genesis_builder_helper::build_state::<RuntimeGenesisConfig>(json)
+				.expect("genesis preset should build valid state");
+		});
+	}
+
+	#[test]
+	fn dev_genesis_preset_is_valid() {
+		assert_genesis_preset_valid(&sp_genesis_builder::DEV_RUNTIME_PRESET.into());
+	}
+
+	#[test]
+	fn local_testnet_genesis_preset_is_valid() {
+		assert_genesis_preset_valid(&sp_genesis_builder::LOCAL_TESTNET_RUNTIME_PRESET.into());
+	}
+}

cumulus/parachains/runtimes/testing/penpal/src/genesis_config_presets.rs

@@ -0,0 +1,10 @@
+title: '[Penpal] fix genesis presets - assign proper ED to accounts'''
+doc:
+- audience: Runtime Dev
+  description: |-
+    Penpal had values below the ED for initializing asset balances for some accounts. This has not been detected as no unit tests actually use the presets. This PR fixes the invalid values, and it also adds some unit tests for validating that the presets build at least.
+
+    Closes #11558.
+crates:
+- name: penpal-runtime
+  bump: patch