From f4f2cee5d2bf42add907e2e6b16c1da180b6ee29 Mon Sep 17 00:00:00 2001
From: Moritz Zielke <moritz.zielke@gmail.com>
Date: Tue, 3 Mar 2026 09:46:27 +0100
Subject: [PATCH] test: `Felt` constructor edge cases

---
 .../src/rust_masm_tests/constructors.rs       | 56 +++++++++++++++++++
 tests/integration/src/rust_masm_tests/mod.rs  |  1 +
 2 files changed, 57 insertions(+)
 create mode 100644 tests/integration/src/rust_masm_tests/constructors.rs

diff --git a/tests/integration/src/rust_masm_tests/constructors.rs b/tests/integration/src/rust_masm_tests/constructors.rs
new file mode 100644
index 000000000..2e4429a55
--- /dev/null
+++ b/tests/integration/src/rust_masm_tests/constructors.rs
@@ -0,0 +1,56 @@
+use miden_core::{Felt, StarkField};
+use miden_debug::ToMidenRepr;
+use midenc_frontend_wasm::WasmTranslationConfig;
+
+use crate::{CompilerTest, testing::eval_package};
+
+#[test]
+fn test_felt_construction_edge_cases() {
+    // Return `0` zero as sentinel value for failure of constructing the Felt.
+    // This avoids having to deal with panics.
+    let main_fn = r#"(x: u64) -> Felt {
+        Felt::new(x).unwrap_or(Felt::new(0u64).unwrap())
+    }
+    "#;
+    let config = WasmTranslationConfig::default();
+    let mut test = CompilerTest::rust_fn_body_with_stdlib_sys(
+        "felt_constructor_edge_case",
+        main_fn,
+        config,
+        None,
+    );
+    let package = test.compile_package();
+
+    // (input, expected_out) with `expected_out = None` if Felt construction is expected to fail.
+    let cases: Vec<(u64, Option<u64>)> = Vec::from([
+        (1, Some(1)),
+        (Felt::MODULUS - 1, Some(Felt::MODULUS - 1)),
+        // failure as these values do not fit into Felt
+        (Felt::MODULUS, None),
+        (Felt::MODULUS + 1, None),
+        (u64::MAX, None),
+    ]);
+
+    for (input, expected_out) in cases {
+        let mut args = Vec::<midenc_hir::Felt>::default();
+        input.push_to_operand_stack(&mut args);
+        eval_package::<Felt, _, _>(&package, [], &args, &test.session, |trace| {
+            let expected_out = match expected_out {
+                Some(out) => {
+                    assert!(
+                        out != 0,
+                        "don't explicitly expect 0, it is the sentinel value for error"
+                    );
+                    out
+                }
+                None => 0,
+            };
+
+            let res: Felt = trace.parse_result().unwrap();
+            println!("input: {input}");
+            assert_eq!(res.as_int(), expected_out);
+            Ok(())
+        })
+        .unwrap();
+    }
+}
diff --git a/tests/integration/src/rust_masm_tests/mod.rs b/tests/integration/src/rust_masm_tests/mod.rs
index 649e4b58c..360fc67d2 100644
--- a/tests/integration/src/rust_masm_tests/mod.rs
+++ b/tests/integration/src/rust_masm_tests/mod.rs
@@ -12,6 +12,7 @@ use crate::testing::eval_package;
 
 mod abi_transform;
 mod apps;
+mod constructors;
 mod debug_source_locations;
 mod examples;
 mod instructions;