fix precompile tests, add precompile test cases from besu-native (#18)

* fix precompile tests, add precompile test cases from besu-native

Signed-off-by: garyschulte <garyschulte@gmail.com>

Author: garyschulte

build.zig

@@ -533,9 +533,22 @@ pub fn build(b: *std.Build) void {
     const run_handler_tests = b.addRunArtifact(handler_tests);
     test_step.dependOn(&run_handler_tests.step);
 
-    // Precompile unit tests - these are run via zig test command in CI
-    // The command needs to link libc and include all modules
-    // See .github/workflows/ci.yml for the full command
+    // Precompile unit tests (runs tests.zig + bn254_tests.zig etc. via main.zig)
+    const precompile_tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = .{ .src_path = .{ .owner = b, .sub_path = "src/precompile/main.zig" } },
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+    precompile_tests.root_module.addImport("primitives", primitives_module);
+    precompile_tests.root_module.addImport("zevm_allocator", zevm_allocator_module);
+    precompile_tests.root_module.addImport("precompile_types", precompile_types_module);
+    precompile_tests.root_module.addImport("precompile_implementations", native_impls_module);
+    precompile_tests.root_module.addImport("build_options", lib_options_module);
+    addCryptoLibraries(b, precompile_tests, enable_blst, enable_mcl, blst_include_path, mcl_include_path, is_windows, target_info.os.tag == .macos);
+    const run_precompile_tests = b.addRunArtifact(precompile_tests);
+    test_step.dependOn(&run_precompile_tests.step);
 
     // Example executable
     const example_exe = b.addExecutable(.{

src/precompile/bls12_381.zig

@@ -356,12 +356,11 @@ pub fn bls12G2MsmRun(input: []const u8, gas_limit: u64) T.PrecompileResult {
 
 /// BLS12-381 pairing check
 pub fn bls12PairingRun(input: []const u8, gas_limit: u64) T.PrecompileResult {
-    if (input.len < PADDED_G1_LENGTH + PADDED_G2_LENGTH) {
-        return T.PrecompileResult{ .err = T.PrecompileError.Bls12381PairingInputLength };
-    }
-
     const pair_len = PADDED_G1_LENGTH + PADDED_G2_LENGTH;
-    if (input.len % pair_len != 0) {
+
+    // EIP-2537: input must be a non-zero multiple of pair_len (384 bytes).
+    // Empty input is explicitly invalid per the spec and execution-spec-tests.
+    if (input.len == 0 or input.len % pair_len != 0) {
         return T.PrecompileResult{ .err = T.PrecompileError.Bls12381PairingInputLength };
     }