diff --git a/contracts/token/src/erc20/mod.rs b/contracts/token/src/erc20/mod.rs
index 81beacac..e993f98a 100644
--- a/contracts/token/src/erc20/mod.rs
+++ b/contracts/token/src/erc20/mod.rs
@@ -383,7 +383,35 @@ mod tests {
     fn reads_balance() {
         test_utils::with_storage::<ERC20>(|token| {
             let balance = token.balance_of(Address::ZERO);
-            assert_eq!(balance, U256::ZERO);
+            assert_eq!(U256::ZERO, balance);
+
+            let owner = msg::sender();
+            let one = U256::from(1);
+            token._balances.setter(owner).set(one);
+            let balance = token.balance_of(owner);
+            assert_eq!(one, balance);
+        })
+    }
+
+    #[test]
+    fn transfers() {
+        test_utils::with_storage::<ERC20>(|token| {
+            let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
+            let bob = address!("B0B0cB49ec2e96DF5F5fFB081acaE66A2cBBc2e2");
+
+            // Alice approves `msg::sender`.
+            let one = U256::from(1);
+            token._allowances.setter(alice).setter(msg::sender()).set(one);
+
+            // Mint some tokens for Alice.
+            let two = U256::from(2);
+            token._balances.setter(alice).set(two);
+            assert_eq!(two, token.balance_of(alice));
+
+            token.transfer_from(alice, bob, one).unwrap();
+
+            assert_eq!(one, token.balance_of(alice));
+            assert_eq!(one, token.balance_of(bob));
         })
     }
 
@@ -410,7 +438,7 @@ mod tests {
     }
 
     #[test]
-    fn transfer_errors_when_insufficient_balance() {
+    fn transfer_from_errors_when_insufficient_balance() {
         test_utils::with_storage::<ERC20>(|token| {
             let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
             let bob = address!("B0B0cB49ec2e96DF5F5fFB081acaE66A2cBBc2e2");
@@ -427,7 +455,27 @@ mod tests {
     }
 
     #[test]
-    fn transfer_errors_when_insufficient_allowance() {
+    fn transfer_from_errors_when_invalid_sender() {
+        test_utils::with_storage::<ERC20>(|token| {
+            let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
+            let one = U256::from(1);
+            let result = token.transfer_from(Address::ZERO, alice, one);
+            assert!(matches!(result, Err(Error::InvalidSender(_))));
+        })
+    }
+
+    #[test]
+    fn transfer_from_errors_when_invalid_receiver() {
+        test_utils::with_storage::<ERC20>(|token| {
+            let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
+            let one = U256::from(1);
+            let result = token.transfer_from(alice, Address::ZERO, one);
+            assert!(matches!(result, Err(Error::InvalidReceiver(_))));
+        })
+    }
+
+    #[test]
+    fn transfer_from_errors_when_insufficient_allowance() {
         test_utils::with_storage::<ERC20>(|token| {
             let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
             let bob = address!("B0B0cB49ec2e96DF5F5fFB081acaE66A2cBBc2e2");
@@ -441,4 +489,42 @@ mod tests {
             assert!(matches!(result, Err(Error::InsufficientAllowance(_))));
         })
     }
+
+    #[test]
+    fn reads_allowance() {
+        test_utils::with_storage::<ERC20>(|token| {
+            let owner = msg::sender();
+            let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
+
+            let allowance = token.allowance(owner, alice);
+            assert_eq!(U256::ZERO, allowance);
+
+            let one = U256::from(1);
+            token._allowances.setter(owner).setter(alice).set(one);
+            let allowance = token.allowance(owner, alice);
+            assert_eq!(one, allowance);
+        })
+    }
+
+    #[test]
+    fn approves() {
+        test_utils::with_storage::<ERC20>(|token| {
+            let alice = address!("A11CEacF9aa32246d767FCCD72e02d6bCbcC375d");
+
+            // `msg::sender` approves Alice.
+            let one = U256::from(1);
+            token.approve(alice, one).unwrap();
+            assert_eq!(one, token._allowances.get(msg::sender()).get(alice));
+        })
+    }
+
+    #[test]
+    fn approve_errors_when_invalid_spender() {
+        test_utils::with_storage::<ERC20>(|token| {
+            // `msg::sender` approves `Address::ZERO`.
+            let one = U256::from(1);
+            let result = token.approve(Address::ZERO, one);
+            assert!(matches!(result, Err(Error::InvalidSpender(_))));
+        })
+    }
 }
diff --git a/lib/wavm-shims/src/lib.rs b/lib/wavm-shims/src/lib.rs
index b32e935e..d76bbb38 100644
--- a/lib/wavm-shims/src/lib.rs
+++ b/lib/wavm-shims/src/lib.rs
@@ -3,6 +3,9 @@
 //! Most of the documentation is taken from the [Stylus source].
 //!
 //! [Stylus source]: https://github.com/OffchainLabs/stylus/blob/484efac4f56fb70f96d4890748b8ec2543d88acd/arbitrator/wasm-libraries/user-host-trait/src/lib.rs
+//!
+//! We allow unsafe here because safety is guaranteed by the Stylus team.
+#![allow(clippy::missing_safety_doc)]
 use std::slice;
 
 use storage::{read_bytes32, write_bytes32, STORAGE};
@@ -76,7 +79,7 @@ pub unsafe extern "C" fn storage_store_bytes32(
     STORAGE.lock().unwrap().insert(key, value);
 }
 
-///
+/// Dummy msg sender set for tests.
 pub const MSG_SENDER: &[u8; 42] = b"0xDeaDbeefdEAdbeefdEadbEEFdeadbeEFdEaDbeeF";
 
 /// Gets the address of the account that called the program. For normal
@@ -95,3 +98,19 @@ pub unsafe extern "C" fn msg_sender(sender: *mut u8) {
     let addr = const_hex::const_decode_to_array::<20>(MSG_SENDER).unwrap();
     std::ptr::copy(addr.as_ptr(), sender, 20);
 }
+
+/// Emits an EVM log with the given number of topics and data, the first bytes
+/// of which should be the 32-byte-aligned topic data. The semantics are
+/// equivalent to that of the EVM's [`LOG0`], [`LOG1`], [`LOG2`], [`LOG3`], and
+/// [`LOG4`] opcodes based on the number of topics specified. Requesting more
+/// than `4` topics will induce a revert.
+///
+/// [`LOG0`]: https://www.evm.codes/#a0
+/// [`LOG1`]: https://www.evm.codes/#a1
+/// [`LOG2`]: https://www.evm.codes/#a2
+/// [`LOG3`]: https://www.evm.codes/#a3
+/// [`LOG4`]: https://www.evm.codes/#a4
+#[no_mangle]
+pub unsafe extern "C" fn emit_log(_: *const u8, _: usize, _: usize) {
+    // No-op: we don't check for events in our unit-tests.
+}