Add tests for split() from Uninitialized account where dest=source (#23442)

programs/stake/src/stake_state.rs

@@ -3959,8 +3959,35 @@ mod tests {
             Err(InstructionError::MissingRequiredSignature)
         );
 
+        let signers = HashSet::from([stake_pubkey]);
+
+        // splitting an uninitialized account where the destination is the same as the source
+        {
+            // splitting should work when...
+            // - when split amount is the full balance
+            // - when split amount is zero
+            // - when split amount is non-zero and less than the full balance
+            //
+            // and splitting should fail when the split amount is greater than the balance
+            assert_eq!(
+                stake_keyed_account.split(stake_lamports, &stake_keyed_account, &signers),
+                Ok(()),
+            );
+            assert_eq!(
+                stake_keyed_account.split(0, &stake_keyed_account, &signers),
+                Ok(()),
+            );
+            assert_eq!(
+                stake_keyed_account.split(stake_lamports / 2, &stake_keyed_account, &signers),
+                Ok(()),
+            );
+            assert_eq!(
+                stake_keyed_account.split(stake_lamports + 1, &stake_keyed_account, &signers),
+                Err(InstructionError::InsufficientFunds),
+            );
+        }
+
         // this should work
-        let signers = vec![stake_pubkey].into_iter().collect();
         assert_eq!(
             stake_keyed_account.split(stake_lamports / 2, &split_stake_keyed_account, &signers),
             Ok(())
@@ -3982,18 +4009,23 @@ mod tests {
             &id(),
         )
         .expect("stake_account");
+        let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
+        let signers = vec![stake_pubkey].into_iter().collect();
 
+        for split_stake_state in &[
+            StakeState::Initialized(Meta::default()),
+            StakeState::Stake(Meta::default(), Stake::default()),
+            StakeState::RewardsPool,
+        ] {
             let split_stake_pubkey = solana_sdk::pubkey::new_rand();
             let split_stake_account = AccountSharedData::new_ref_data_with_space(
                 0,
-            &StakeState::Initialized(Meta::auto(&stake_pubkey)),
+                split_stake_state,
                 std::mem::size_of::<StakeState>(),
                 &id(),
             )
-        .expect("stake_account");
+            .expect("split_stake_account");
 
-        let signers = vec![stake_pubkey].into_iter().collect();
-        let stake_keyed_account = KeyedAccount::new(&stake_pubkey, true, &stake_account);
             let split_stake_keyed_account =
                 KeyedAccount::new(&split_stake_pubkey, true, &split_stake_account);
             assert_eq!(
@@ -4001,6 +4033,7 @@ mod tests {
                 Err(InstructionError::InvalidAccountData)
             );
         }
+    }
     fn just_stake(stake: u64) -> Stake {
         Stake {
             delegation: Delegation {