miden_core/mast/node/basic_block_node/

arbitrary.rs

use alloc::{collections::BTreeMap, sync::Arc};
use core::ops::RangeInclusive;

use proptest::{arbitrary::Arbitrary, prelude::*};

use super::*;
use crate::{
    Felt, Word,
    advice::AdviceMap,
    mast::{
        CallNodeBuilder, DecoratorId, DynNodeBuilder, ExternalNodeBuilder, JoinNodeBuilder,
        LoopNodeBuilder, SplitNodeBuilder,
    },
    operations::{AssemblyOp, DebugOptions, Decorator, Operation},
    program::{Kernel, Program},
};

// Strategy for operations without immediate values (non-control flow)
pub fn op_no_imm_strategy() -> impl Strategy<Value = Operation> {
    prop_oneof![
        Just(Operation::Add),
        Just(Operation::Mul),
        Just(Operation::Neg),
        Just(Operation::Inv),
        Just(Operation::Incr),
        Just(Operation::And),
        Just(Operation::Or),
        Just(Operation::Not),
        Just(Operation::Eq),
        Just(Operation::Eqz),
        Just(Operation::Drop),
        Just(Operation::Pad),
        Just(Operation::Swap),
        Just(Operation::SwapW),
        Just(Operation::SwapW2),
        Just(Operation::SwapW3),
        Just(Operation::SwapDW),
        Just(Operation::MovUp2),
        Just(Operation::MovUp3),
        Just(Operation::MovUp4),
        Just(Operation::MovUp5),
        Just(Operation::MovUp6),
        Just(Operation::MovUp7),
        Just(Operation::MovUp8),
        Just(Operation::MovDn2),
        Just(Operation::MovDn3),
        Just(Operation::MovDn4),
        Just(Operation::MovDn5),
        Just(Operation::MovDn6),
        Just(Operation::MovDn7),
        Just(Operation::MovDn8),
        Just(Operation::CSwap),
        Just(Operation::CSwapW),
        Just(Operation::Dup0),
        Just(Operation::Dup1),
        Just(Operation::Dup2),
        Just(Operation::Dup3),
        Just(Operation::Dup4),
        Just(Operation::Dup5),
        Just(Operation::Dup6),
        Just(Operation::Dup7),
        Just(Operation::Dup9),
        Just(Operation::Dup11),
        Just(Operation::Dup13),
        Just(Operation::Dup15),
        Just(Operation::MLoad),
        Just(Operation::MStore),
        Just(Operation::MLoadW),
        Just(Operation::MStoreW),
        Just(Operation::MStream),
        Just(Operation::Pipe),
        Just(Operation::AdvPop),
        Just(Operation::AdvPopW),
        Just(Operation::U32split),
        Just(Operation::U32add),
        Just(Operation::U32sub),
        Just(Operation::U32mul),
        Just(Operation::U32div),
        Just(Operation::U32and),
        Just(Operation::U32xor),
        Just(Operation::U32add3),
        Just(Operation::U32madd),
        Just(Operation::SDepth),
        Just(Operation::Caller),
        Just(Operation::Clk),
        Just(Operation::Emit),
        Just(Operation::Ext2Mul),
        Just(Operation::Expacc),
        Just(Operation::HPerm),
        // Note: We exclude Assert here because it has an immediate value (error code)
    ]
}

// Strategy for operations with immediate values
pub fn op_with_imm_strategy() -> impl Strategy<Value = Operation> {
    prop_oneof![any::<u64>().prop_map(Felt::new).prop_map(Operation::Push)]
}

// Strategy for all non-control flow operations
pub fn op_non_control_strategy() -> impl Strategy<Value = Operation> {
    prop_oneof![op_no_imm_strategy(), op_with_imm_strategy(),]
}

// Strategy for sequences of operations
pub fn op_non_control_sequence_strategy(
    max_length: usize,
) -> impl Strategy<Value = Vec<Operation>> {
    prop::collection::vec(op_non_control_strategy(), 1..=max_length)
}

// ---------- Parameters ----------

/// Parameters for generating BasicBlockNode instances
#[derive(Clone, Debug)]
pub struct BasicBlockNodeParams {
    /// Maximum number of operations in a generated basic block
    pub max_ops_len: usize,
    /// Maximum number of decorator pairs in a generated basic block
    pub max_pairs: usize,
    /// Maximum value for decorator IDs (u32)
    pub max_decorator_id_u32: u32,
}

impl Default for BasicBlockNodeParams {
    fn default() -> Self {
        Self {
            max_ops_len: 8,
            max_pairs: 2,
            max_decorator_id_u32: 3,
        }
    }
}

// ---------- DecoratorId strategy ----------

/// Strategy for generating DecoratorId values
pub fn decorator_id_strategy(max_id: u32) -> impl Strategy<Value = DecoratorId> {
    // max_id == 0 would be degenerate; clamp to at least 1
    let upper = core::cmp::max(1, max_id);
    (0..upper).prop_map(DecoratorId::new_unchecked)
}

// ---------- Decorator pairs strategy ----------

/// Strategy for generating decorator pairs (usize, DecoratorId)
pub fn decorator_pairs_strategy(
    ops_len: usize,
    max_id: u32,
    max_pairs: usize,
) -> impl Strategy<Value = Vec<(usize, DecoratorId)>> {
    // indices in [0, ops_len] inclusive; size 0..=max_pairs
    // Generate, then sort by index to match validation expectations
    prop::collection::vec((0..=ops_len, decorator_id_strategy(max_id)), 0..=max_pairs).prop_map(
        |mut v| {
            v.sort_by_key(|(i, _)| *i);
            v
        },
    )
}

// ---------- Arbitrary for BasicBlockNode ----------

impl Arbitrary for BasicBlockNode {
    type Parameters = BasicBlockNodeParams;
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(p: Self::Parameters) -> Self::Strategy {
        // ensure at least 1 op to satisfy BasicBlockNode::new
        (op_non_control_sequence_strategy(p.max_ops_len),)
            .prop_flat_map(move |(ops,)| {
                let ops_len = ops.len().max(1); // defensive; strategy should ensure ≥1
                decorator_pairs_strategy(ops_len, p.max_decorator_id_u32, p.max_pairs)
                    .prop_map(move |decorators| (ops.clone(), decorators))
            })
            .prop_filter_map("non-empty ops", |(ops, decorators)| {
                if ops.is_empty() { None } else { Some((ops, decorators)) }
            })
            .prop_map(|(ops, decorators)| {
                // BasicBlockNode::new_owned_with_decorators will adjust indices for padding and set
                // be/ae empty.
                BasicBlockNode::new_owned_with_decorators(ops, decorators)
                    .expect("non-empty ops; new() only errs on empty ops")
            })
            .boxed()
    }
}

// ---------- Optional: MastForest strategy (behind feature gate) ----------

/// Parameters for generating MastForest instances
///
/// # Execution Compatibility
///
/// Generated forests will only be executable if certain node types are excluded:
/// - **Syscalls**: Require matching kernel procedures. Set `max_syscalls = 0` for executable
///   forests.
/// - **Externals**: Use random digests that won't match valid procedures. Set `max_externals = 0`
///   for executable forests.
/// - **Dyn nodes**: Leave junk on the stack and cannot execute properly. Set `max_dyns = 0` for
///   executable forests.
///
/// The default parameters create executable forests by setting all three of the above to 0.
///
/// # Non-executable Forests
///
/// If you want to generate forests for testing assembly or parsing without execution:
/// - Set `max_syscalls > 0` to include syscall nodes
/// - Set `max_externals > 0` to include external nodes
/// - Set `max_dyns > 0` to include dynamic nodes
///
/// These forests are useful for testing MAST structure and serialization but will fail during
/// execution.
#[derive(Clone, Debug)]
pub struct MastForestParams {
    /// Number of decorators to generate
    pub decorators: u32,
    /// Range of number of blocks to generate
    pub blocks: RangeInclusive<usize>,
    /// Maximum number of join nodes to generate
    pub max_joins: usize,
    /// Maximum number of split nodes to generate
    pub max_splits: usize,
    /// Maximum number of loop nodes to generate
    pub max_loops: usize,
    /// Maximum number of call nodes to generate
    pub max_calls: usize,
    /// Maximum number of syscall nodes to generate
    ///
    /// **Warning**: Syscalls require a properly configured kernel with matching procedure hashes.
    /// Generated syscalls use random procedure digests and will not execute without providing
    /// a matching kernel. Set to 0 for executable forests.
    pub max_syscalls: usize,
    /// Maximum number of external nodes to generate
    ///
    /// **Warning**: External nodes use random digests that won't correspond to valid procedures.
    /// Any program with external nodes will fail to execute. Set to 0 for executable forests.
    pub max_externals: usize,
    /// Maximum number of dyn/dyncall nodes to generate
    ///
    /// **Warning**: Dyn nodes leave junk on the stack and cannot execute properly.
    /// These nodes are primarily for testing MAST structure, not execution. Set to 0 for
    /// executable forests.
    pub max_dyns: usize,
}

impl Default for MastForestParams {
    fn default() -> Self {
        Self {
            decorators: 3,
            blocks: 1..=3,
            max_joins: 1,
            max_splits: 1,
            max_loops: 1,
            max_calls: 1,
            max_syscalls: 0,  // Default to 0 for executable forests
            max_externals: 0, // Default to 0 for executable forests
            max_dyns: 0,      // Default to 0 for executable forests
        }
    }
}

impl Arbitrary for MastForest {
    type Parameters = MastForestParams;
    type Strategy = BoxedStrategy<Self>;

    /// Generates a MastForest with the specified parameters.
    ///
    /// # Generated Forest Properties
    ///
    /// - **Basic blocks**: Always generated (1..=blocks.end()) with operations and decorators
    /// - **Control flow nodes**: Generated according to max_* parameters, may be 0
    /// - **Root nodes**: ~1/3 of generated nodes are marked as roots
    ///
    /// # Execution Limitations
    ///
    /// Generated forests may not be executable depending on parameters:
    ///
    /// ## Syscalls (`max_syscalls`)
    /// - Generated syscalls reference random procedure digests
    /// - Execution requires a kernel containing matching procedure hashes
    /// - For executable forests, set `max_syscalls = 0`
    ///
    /// ## External Nodes (`max_externals`)
    /// - Generated with random digests that won't match valid procedures
    /// - Any program with external nodes will fail during execution
    /// - For executable forests, set `max_externals = 0`
    ///
    /// ## Dynamic Nodes (`max_dyns`)
    /// - Dyn and dyncall nodes leave junk on the stack
    /// - These nodes cannot execute properly in practice
    /// - For executable forests, set `max_dyns = 0`
    ///
    /// # Example Usage
    ///
    /// ```rust
    /// use miden_core::mast::{MastForest, arbitrary::MastForestParams};
    /// use proptest::arbitrary::Arbitrary;
    ///
    /// // Generate executable forest (default)
    /// let forest = MastForest::arbitrary_with(MastForestParams::default());
    ///
    /// // Generate forest with non-executable nodes for testing
    /// let params = MastForestParams {
    ///     max_syscalls: 2,
    ///     max_externals: 1,
    ///     max_dyns: 1,
    ///     ..Default::default()
    /// };
    /// let forest = MastForest::arbitrary_with(params);
    /// ```
    fn arbitrary_with(params: Self::Parameters) -> Self::Strategy {
        // BasicBlockNode generation must reference decorator IDs in [0, decorators)
        let bb_params = BasicBlockNodeParams {
            max_decorator_id_u32: params.decorators,
            ..Default::default()
        };

        // Generate nodes in a way that respects topological ordering
        (
            // Generate basic blocks first (they have no dependencies)
            prop::collection::vec(
                any_with::<BasicBlockNode>(bb_params.clone()),
                1..=*params.blocks.end(),
            ),
            // Generate decorators
            prop::collection::vec(
                any::<Decorator>(),
                params.decorators as usize..=params.decorators as usize,
            ),
            // Generate control flow node counts within the specified limits
            (
                // Generate number of join nodes (0 to max_joins)
                0..=params.max_joins,
                // Generate number of split nodes (0 to max_splits)
                0..=params.max_splits,
                // Generate number of loop nodes (0 to max_loops)
                0..=params.max_loops,
                // Generate number of call nodes (0 to max_calls)
                0..=params.max_calls,
                // Generate number of syscall nodes (0 to max_syscalls)
                0..=params.max_syscalls,
                // Generate number of external nodes (0 to max_externals)
                0..=params.max_externals,
                // Generate number of dyn nodes (0 to max_dyns)
                0..=params.max_dyns,
            ),
        )
            .prop_flat_map(
                move |(
                    basic_blocks,
                    decorators,
                    (
                        num_joins,
                        num_splits,
                        num_loops,
                        num_calls,
                        num_syscalls,
                        num_externals,
                        num_dyns,
                    ),
                )| {
                    let num_basic_blocks = basic_blocks.len();

                    // Ensure we have enough basic blocks for parents to reference
                    let max_parent_nodes = num_basic_blocks.saturating_sub(1);
                    let num_joins = num_joins.min(max_parent_nodes);
                    let num_splits = num_splits.min(max_parent_nodes);
                    let num_loops = num_loops.min(num_basic_blocks);
                    let num_calls = num_calls.min(num_basic_blocks);
                    let num_syscalls = num_syscalls.min(num_basic_blocks);

                    // Generate indices for creating parent nodes
                    (
                        Just(basic_blocks),
                        Just(decorators),
                        Just((
                            num_joins,
                            num_splits,
                            num_loops,
                            num_calls,
                            num_syscalls,
                            num_externals,
                            num_dyns,
                        )),
                        // Generate indices for join nodes (need 2 children each)
                        prop::collection::vec(any::<(usize, usize)>(), num_joins..=num_joins)
                            .prop_map(move |pairs| {
                                pairs
                                    .into_iter()
                                    .map(|(a, b)| (a % num_basic_blocks, b % num_basic_blocks))
                                    .collect::<Vec<_>>()
                            }),
                        // Generate indices for split nodes (need 2 children each)
                        prop::collection::vec(any::<(usize, usize)>(), num_splits..=num_splits)
                            .prop_map(move |pairs| {
                                pairs
                                    .into_iter()
                                    .map(|(a, b)| (a % num_basic_blocks, b % num_basic_blocks))
                                    .collect::<Vec<_>>()
                            }),
                        // Generate indices for loop nodes (need 1 child each)
                        prop::collection::vec(any::<usize>(), num_loops..=num_loops).prop_map(
                            move |indices| {
                                indices
                                    .into_iter()
                                    .map(|i| i % num_basic_blocks)
                                    .collect::<Vec<_>>()
                            },
                        ),
                        // Generate indices for call nodes (need 1 child each)
                        prop::collection::vec(any::<usize>(), num_calls..=num_calls).prop_map(
                            move |indices| {
                                indices
                                    .into_iter()
                                    .map(|i| i % num_basic_blocks)
                                    .collect::<Vec<_>>()
                            },
                        ),
                        // Generate indices for syscall nodes (need 1 child each)
                        prop::collection::vec(any::<usize>(), num_syscalls..=num_syscalls)
                            .prop_map(move |indices| {
                                indices
                                    .into_iter()
                                    .map(|i| i % num_basic_blocks)
                                    .collect::<Vec<_>>()
                            }),
                        // Generate digests for external nodes
                        prop::collection::vec(any::<[u64; 4]>(), num_externals..=num_externals)
                            .prop_map(move |digests| {
                                digests
                                    .into_iter()
                                    .map(|[a, b, c, d]| {
                                        Word::from([
                                            Felt::new(a),
                                            Felt::new(b),
                                            Felt::new(c),
                                            Felt::new(d),
                                        ])
                                    })
                                    .collect::<Vec<_>>()
                            }),
                    )
                },
            )
            .prop_map(
                move |(
                    basic_blocks,
                    decorators,
                    (
                        _num_joins,
                        _num_splits,
                        _num_loops,
                        _num_calls,
                        _num_syscalls,
                        _num_externals,
                        num_dyns,
                    ),
                    join_pairs,
                    split_pairs,
                    loop_indices,
                    call_indices,
                    syscall_indices,
                    external_digests,
                )| {
                    let mut forest = MastForest::new();

                    // 1) Add all decorators first
                    for decorator in decorators {
                        forest.add_decorator(decorator).expect("Failed to add decorator");
                    }

                    // 2) Add basic blocks and collect their IDs
                    let mut basic_block_ids = Vec::new();
                    for block in basic_blocks {
                        let builder = block.to_builder(&forest);
                        let node_id =
                            builder.add_to_forest(&mut forest).expect("Failed to add block");
                        basic_block_ids.push(node_id);
                    }

                    // 3) Add control flow nodes in topological order (children already exist)
                    let mut all_node_ids = basic_block_ids.clone();

                    // Add join nodes
                    for &(left_idx, right_idx) in &join_pairs {
                        if left_idx < all_node_ids.len() && right_idx < all_node_ids.len() {
                            let left_id = all_node_ids[left_idx];
                            let right_id = all_node_ids[right_idx];
                            if let Ok(join_id) =
                                JoinNodeBuilder::new([left_id, right_id]).add_to_forest(&mut forest)
                            {
                                all_node_ids.push(join_id);
                            }
                        }
                    }

                    // Add split nodes
                    for &(true_idx, false_idx) in &split_pairs {
                        if true_idx < all_node_ids.len() && false_idx < all_node_ids.len() {
                            let true_id = all_node_ids[true_idx];
                            let false_id = all_node_ids[false_idx];
                            if let Ok(split_id) = SplitNodeBuilder::new([true_id, false_id])
                                .add_to_forest(&mut forest)
                            {
                                all_node_ids.push(split_id);
                            }
                        }
                    }

                    // Add loop nodes
                    for &body_idx in &loop_indices {
                        if body_idx < all_node_ids.len() {
                            let body_id = all_node_ids[body_idx];
                            if let Ok(loop_id) =
                                LoopNodeBuilder::new(body_id).add_to_forest(&mut forest)
                            {
                                all_node_ids.push(loop_id);
                            }
                        }
                    }

                    // Add call nodes
                    for &callee_idx in &call_indices {
                        if callee_idx < all_node_ids.len() {
                            let callee_id = all_node_ids[callee_idx];
                            let call_id =
                                CallNodeBuilder::new(callee_id).add_to_forest(&mut forest).unwrap();
                            all_node_ids.push(call_id);
                        }
                    }

                    // Add syscall nodes
                    // WARNING: These use random procedure digests and will not execute without a
                    // matching kernel
                    for &callee_idx in &syscall_indices {
                        if callee_idx < all_node_ids.len() {
                            let callee_id = all_node_ids[callee_idx];
                            let syscall_id = CallNodeBuilder::new_syscall(callee_id)
                                .add_to_forest(&mut forest)
                                .unwrap();
                            all_node_ids.push(syscall_id);
                        }
                    }

                    // Add external nodes
                    // WARNING: These use random digests that won't match any valid procedures
                    for digest in external_digests {
                        if let Ok(external_id) =
                            ExternalNodeBuilder::new(digest).add_to_forest(&mut forest)
                        {
                            all_node_ids.push(external_id);
                        }
                    }

                    // Add dyn nodes (mix of dyn and dyncall)
                    // WARNING: These leave junk on the stack and cannot execute properly
                    for i in 0..num_dyns {
                        let dyn_id = if i % 2 == 0 {
                            DynNodeBuilder::new_dyn().add_to_forest(&mut forest).unwrap()
                        } else {
                            DynNodeBuilder::new_dyncall().add_to_forest(&mut forest).unwrap()
                        };
                        all_node_ids.push(dyn_id);
                    }

                    // 4) Make some nodes roots (but not all, to test internal nodes)
                    let num_roots = (all_node_ids.len() / 3).max(1); // Make roughly 1/3 of nodes roots
                    for (i, &node_id) in all_node_ids.iter().enumerate() {
                        if i % (all_node_ids.len() / num_roots.max(1)) == 0 {
                            forest.make_root(node_id);
                        }
                    }

                    forest
                },
            )
            .boxed()
    }
}

// ---------- Arbitrary implementations for missing types ----------

impl Arbitrary for DebugOptions {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        prop_oneof![
            Just(DebugOptions::StackAll),
            any::<u8>().prop_map(DebugOptions::StackTop),
            Just(DebugOptions::MemAll),
            (any::<u32>(), any::<u32>())
                .prop_map(|(start, end)| DebugOptions::MemInterval(start, end)),
            (any::<u16>(), any::<u16>(), any::<u16>()).prop_map(|(start, end, num_locals)| {
                DebugOptions::LocalInterval(start, end, num_locals)
            }),
            any::<u16>().prop_map(DebugOptions::AdvStackTop),
        ]
        .boxed()
    }
}

impl Arbitrary for AssemblyOp {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        (
            any::<bool>(),
            prop::collection::vec(any::<char>(), 1..=20)
                .prop_map(|chars| chars.into_iter().collect()),
            prop::collection::vec(any::<char>(), 1..=20)
                .prop_map(|chars| chars.into_iter().collect()),
            any::<u8>(),
        )
            .prop_map(|(has_location, context_name, op, num_cycles)| {
                use miden_debug_types::{ByteIndex, Location, Uri};

                let location = if has_location {
                    Some(Location::new(Uri::new("dummy.rs"), ByteIndex(0), ByteIndex(0)))
                } else {
                    None
                };

                AssemblyOp::new(location, context_name, num_cycles, op)
            })
            .boxed()
    }
}

impl Arbitrary for Decorator {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        prop_oneof![
            any_with::<DebugOptions>(()).prop_map(Decorator::Debug),
            any::<u32>().prop_map(Decorator::Trace),
        ]
        .boxed()
    }
}

impl Arbitrary for AdviceMap {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        // Strategy for generating Word keys
        let word_strategy = prop_oneof![
            Just(Word::default()),
            any::<[u64; 4]>().prop_map(|[a, b, c, d]| Word::new([
                Felt::new(a),
                Felt::new(b),
                Felt::new(c),
                Felt::new(d)
            ])),
        ];

        // Strategy for generating Arc<[Felt]> values
        let felt_array_strategy = prop::collection::vec(any::<u64>(), 1..=4).prop_map(|vals| {
            let felts: Arc<[Felt]> = vals.into_iter().map(Felt::new).collect();
            felts
        });

        // Strategy for generating map entries
        let entry_strategy = (word_strategy, felt_array_strategy);

        // Strategy for generating the map itself (0 to 10 entries)
        prop::collection::vec(entry_strategy, 0..=10)
            .prop_map(|entries| {
                let mut map = BTreeMap::new();
                for (key, value) in entries {
                    map.insert(key, value);
                }
                AdviceMap::from(map)
            })
            .boxed()
    }
}

impl Arbitrary for Program {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        // Create a simple strategy that generates a basic block and creates a program from it
        any_with::<BasicBlockNode>(BasicBlockNodeParams {
            max_ops_len: 4, // Keep it small
            max_pairs: 1,   // Fewer decorators
            max_decorator_id_u32: 2,
        })
        .prop_map(|node| {
            // Create a new MastForest
            let mut forest = MastForest::new();

            // Add some basic decorators
            for i in 0..2 {
                let decorator = Decorator::Trace(i as u32);
                forest.add_decorator(decorator).expect("Failed to add decorator");
            }

            // Add the node to the forest using builder
            let builder = node.to_builder(&forest);
            let node_id = builder.add_to_forest(&mut forest).expect("Failed to add node");

            // Since we added a node, it should be available as a procedure root
            // If not, we need to make it a root manually
            let entrypoint = if forest.num_procedures() > 0 {
                forest.procedure_roots()[0]
            } else {
                // Make the node a root manually
                forest.make_root(node_id);
                // After making it a root, it should be a procedure
                if forest.num_procedures() == 0 {
                    panic!("Failed to create a valid procedure from node");
                }
                forest.procedure_roots()[0]
            };

            Program::new(Arc::new(forest), entrypoint)
        })
        .prop_filter("valid entrypoint", |program| {
            // Ensure the generated program has a valid procedure entrypoint
            program.mast_forest().is_procedure_root(program.entrypoint())
        })
        .boxed()
    }
}

impl Arbitrary for Kernel {
    type Parameters = ();
    type Strategy = BoxedStrategy<Self>;

    fn arbitrary_with(_args: Self::Parameters) -> Self::Strategy {
        // Strategy for generating Word vectors
        let word_strategy = any::<[u64; 4]>().prop_map(|[a, b, c, d]| {
            Word::new([Felt::new(a), Felt::new(b), Felt::new(c), Felt::new(d)])
        });

        // Strategy for generating kernel (0 to 3 words to avoid hitting MAX_NUM_PROCEDURES limit)
        prop::collection::vec(word_strategy, 0..=3)
            .prop_map(|words: Vec<Word>| {
                Kernel::new(&words).expect("Generated kernel should be valid")
            })
            .boxed()
    }
}