[framework, tests] Adds convenience method for testing (#15893)

## Description 

Adds some test-only methods for overall convenience in testing.

## Test Plan 

I am test.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

crates/sui-framework/packages/sui-framework/sources/balance.move

@@ -11,13 +11,10 @@ module sui::balance {
 
     /// For when trying to destroy a non-zero balance.
     const ENonZero: u64 = 0;
-
     /// For when an overflow is happening on Supply operations.
     const EOverflow: u64 = 1;
-
     /// For when trying to withdraw more than there is.
     const ENotEnough: u64 = 2;
-
     /// Sender is not @0x0 the system address.
     const ENotSystemAddress: u64 = 3;
 

crates/sui-framework/packages/sui-framework/sources/bcs.move

@@ -40,10 +40,8 @@ module sui::bcs {
 
     /// For when bytes length is less than required for deserialization.
     const EOutOfRange: u64 = 0;
-
     /// For when the boolean value different than `0` or `1`.
     const ENotBool: u64 = 1;
-
     /// For when ULEB byte is out of range (or not found).
     const ELenOutOfRange: u64 = 2;
 

crates/sui-framework/packages/sui-framework/sources/kiosk/transfer_policy.move

@@ -289,4 +289,18 @@ module sui::transfer_policy {
 
     /// Get the `from` field of the `TransferRequest`.
     public fun from<T>(self: &TransferRequest<T>): ID { self.from }
+
+    // === Tests ===
+
+    #[test_only]
+    /// Create a new TransferPolicy for testing purposes.
+    public fun new_for_testing<T>(ctx: &mut TxContext): (TransferPolicy<T>, TransferPolicyCap<T>) {
+        let id = object::new(ctx);
+        let policy_id = object::uid_to_inner(&id);
+
+        (
+            TransferPolicy { id, rules: vec_set::empty(), balance: balance::zero() },
+            TransferPolicyCap { id: object::new(ctx), policy_id }
+        )
+    }
 }