test: assets precompile using eth address as default example

integration-tests/public/assets-precompile-eth/Cargo.toml

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+[package]
+name = "assets_precompile_eth"
+version = "6.0.0-beta.1"
+authors = ["Use Ink <[email protected]>"]
+edition = "2024"
+publish = false
+
+[dependencies]
+ink = { path = "../../../crates/ink", default-features = false }
+ink_precompiles = { path = "../../../crates/precompiles", default-features = false }
+
+[dev-dependencies]
+ink_e2e = { path = "../../../crates/e2e" }
+ink_sandbox = { path = "../../../crates/sandbox" }
+hex = "0.4"
+
+[lib]
+path = "lib.rs"
+
+[features]
+default = ["std"]
+std = [
+    "ink/std",
+    "ink_precompiles/std",
+]
+ink-as-dependency = []
+e2e-tests = []
+
+[package.metadata.ink-lang]
+abi = "ink"
+
+[lints.rust.unexpected_cfgs]
+level = "warn"
+check-cfg = [
+    'cfg(ink_abi, values("ink", "sol", "all"))'
+]

integration-tests/public/assets-precompile-eth/README.md

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+# Assets Precompile Integration Test (Ethereum-First Approach)
+
+This integration test demonstrates the **recommended approach** for interacting with pallet-revive contracts using Ethereum addresses as the default.
+
+## Why Ethereum Addresses?
+
+When using Substrate addresses (AccountId32) with pallet-revive, you encounter the "fallback account trap":
+
+```
+Substrate AccountId32 (Alice)
+    │
+    ▼ keccak_256()[12..]
+Derived H160 (0xabcd...)
+    │
+    ▼ Contract stores this address
+    │
+    ▼ Later: Contract needs to send tokens back
+    │
+    ▼ to_account_id(0xabcd...) lookup
+    │
+    ├─ IF MAPPED: Returns original AccountId32 ✓
+    │
+    └─ IF NOT MAPPED: Returns FALLBACK account ✗
+                      (0xabcd...EEEEEEEEEEEEEEEEEEEE)
+                      Tokens are effectively lost!
+```
+
+## The Ethereum-First Solution
+
+By using Ethereum keypairs (ECDSA/secp256k1), the address roundtrip is **lossless**:
+
+```
+Ethereum H160 (0x1234...)
+    │
+    ▼ to_account_id()
+Fallback AccountId32 (0x1234...EEEEEEEEEEEEEEEEEEEE)
+    │
+    ▼ to_address() checks is_eth_derived()
+    │
+    ▼ TRUE → strips 0xEE suffix
+    │
+Original H160 (0x1234...) ✓
+```
+
+## Key Differences from Standard Approach
+
+| Aspect | Substrate Approach | Ethereum Approach |
+|--------|-------------------|-------------------|
+| Keypair type | Sr25519 (`alice()`, `bob()`) | ECDSA (`alith()`, `baltathar()`) |
+| Address type | Derived H160 | Native H160 |
+| Mapping required | Yes (`map_account()`) | **No!** |
+| Address roundtrip | Lossy without mapping | Lossless |
+| MetaMask compatible | No | Yes |
+
+## Usage
+
+```rust
+use ink_e2e::eth::{alith, baltathar};
+
+// Use Ethereum keypairs
+let alice = alith();
+let bob = baltathar();
+
+// Get native H160 addresses
+let alice_address = alice.address();
+let bob_address = bob.address();
+
+// No mapping needed - just use them directly with contracts!
+```
+
+## Available Dev Accounts
+
+The following Ethereum dev accounts are available via `ink_e2e::eth::dev`:
+
+- `alith()` - Primary test account
+- `baltathar()` - Secondary test account
+- `charleth()` - Third test account
+- `dorothy()` - Fourth test account
+- `ethan()` - Fifth test account
+- `faith()` - Sixth test account
+- ... and more
+
+## Running the Tests
+
+```bash
+cargo test -p assets_precompile_eth --features e2e-tests
+```