From fdd1305c0c3cf59f9afa06834f11447bb731957c Mon Sep 17 00:00:00 2001
From: Alejandro Cabeza Romero <alex93cabeza@gmail.com>
Date: Wed, 22 Apr 2026 12:05:32 +0200
Subject: [PATCH] Add ffi smoke test.

---
 blend/test_ffi.cpp | 64 ++++++++++++++++++++++++++++++++++++++++++++++
 justfile           | 22 ++++++++++++++++
 2 files changed, 86 insertions(+)
 create mode 100644 blend/test_ffi.cpp

diff --git a/blend/test_ffi.cpp b/blend/test_ffi.cpp
new file mode 100644
index 0000000..16755a0
--- /dev/null
+++ b/blend/test_ffi.cpp
@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "poq/ffi.hpp"
+
+static uint8_t* read_file(const char* path, size_t* out_size) {
+    FILE* f = fopen(path, "rb");
+    if (!f) return nullptr;
+    fseek(f, 0, SEEK_END);
+    *out_size = ftell(f);
+    rewind(f);
+    uint8_t* buf = (uint8_t*)malloc(*out_size + 1);
+    fread(buf, 1, *out_size, f);
+    buf[*out_size] = '\0';
+    fclose(f);
+    return buf;
+}
+
+int main() {
+    Status status = poq_generate_witness_from_files(
+        "poq",
+        "../input.json",
+        "witness.wtns"
+    );
+
+    if (status_is_error(status)) {
+        fprintf(stderr, "Error [%d]: %s\n", status.code, status.message);
+        return 1;
+    }
+
+    printf("generate_witness_from_files: OK\n");
+
+    size_t dat_size, json_size;
+    uint8_t* dat_data = read_file("poq.dat", &dat_size);
+    uint8_t* json_data = read_file("../input.json", &json_size);
+
+    WitnessInput input = {
+        {dat_data, dat_size},
+        (const char*)json_data
+    };
+    Bytes output = {nullptr, 0};
+
+    status = poq_generate_witness(&input, &output);
+
+    free(dat_data);
+    free(json_data);
+
+    if (status_is_error(status)) {
+        fprintf(stderr, "Error [%d]: %s\n", status.code, status.message);
+        return 1;
+    }
+
+    size_t wtns_size;
+    uint8_t* wtns_data = read_file("witness.wtns", &wtns_size);
+    assert(wtns_data != nullptr);
+    assert(output.size == wtns_size);
+    assert(memcmp(output.data, wtns_data, output.size) == 0);
+    free(wtns_data);
+
+    printf("generate_witness: OK (%zu bytes, matches witness.wtns)\n", output.size);
+    free_bytes(&output);
+    return 0;
+}
diff --git a/justfile b/justfile
index 85f4744..7c105f6 100644
--- a/justfile
+++ b/justfile
@@ -1,3 +1,6 @@
+src          := justfile_directory() + "/src"
+ci_makefile  := justfile_directory() + "/.github/resources/witness-generator/Makefile"
+
 prettify:
     nix shell nixpkgs#clang-tools -c clang-format -i src/**.cpp src/**.hpp
 
@@ -10,3 +13,22 @@ sage-run script +args='':
         -v "{{justfile_directory()}}:/work" \
         -w "/work/$(dirname '{{script}}')" \
         sagemath/sagemath sage "$(basename '{{script}}')" {{args}}
+
+# Build the PoQ circuit and its C++ witness generator, equivalent to the CI build.
+poq:
+    circom blend/poq.circom --c --r1cs --no_asm --O2 --output blend
+    # circom-generated main() has no return on the success path; patch it before -O3 turns it into an infinite loop
+    sed -i ':a;N;$!ba;s/\n}\n\n*$/\n  return 0;\n}/' blend/poq_cpp/main.cpp
+    cp -r {{src}}/poq blend/poq_cpp/poq
+    cp {{src}}/circom_adapter.cpp {{src}}/circom_adapter.hpp {{src}}/circom_fwd.hpp {{src}}/types.hpp blend/poq_cpp/
+    cp {{ci_makefile}} blend/poq_cpp/Makefile
+    cp blend/test_ffi.cpp blend/poq_cpp/test_ffi.cpp
+    make -C blend/poq_cpp PROJECT=poq linux-lib
+
+# Run a simple smoke test of the PoQ witness generator.
+test-poq: poq
+    g++ -std=c++11 -O3 -I blend/poq_cpp blend/poq_cpp/test_ffi.cpp -L blend/poq_cpp -lwitness_poq -lgmp -o blend/poq_cpp/test_ffi
+    cd blend/poq_cpp && ./test_ffi
+
+clean:
+    rm -rf blend/poq_cpp