feat: add foreign function support

runner.py

@@ -12,6 +12,7 @@ def run_test(test_file: Path, compiler_bin: Path):
     expected_code = 0
     code_lines = []
     harness_lines = None
+    expected_output_lines = None
     current_section = None
 
     for line in lines:
@@ -20,6 +21,8 @@ def run_test(test_file: Path, compiler_bin: Path):
             current_section = trimmed[1:-1]
             if current_section == "harness":
                 harness_lines = []
+            elif current_section == "expected_output":
+                expected_output_lines = []
         elif current_section:
             if current_section == "expected_return_code":
                 if trimmed:
@@ -28,6 +31,8 @@ def run_test(test_file: Path, compiler_bin: Path):
                 code_lines.append(line)
             elif current_section == "harness":
                 harness_lines.append(line)
+            elif current_section == "expected_output":
+                expected_output_lines.append(line)
 
     code = "".join(code_lines)
     harness = "".join(harness_lines) if harness_lines is not None else None
@@ -75,6 +80,13 @@ def run_test(test_file: Path, compiler_bin: Path):
         if exec_res.returncode != expected_code:
             raise Exception(f"Expected return code {expected_code}, but got {exec_res.returncode}")
 
+        # 4. Check the standard output if expected_output is provided
+        if expected_output_lines is not None:
+            expected_out = "".join(expected_output_lines).strip()
+            actual_out = exec_res.stdout.strip()
+            if expected_out != actual_out:
+                raise Exception(f"Expected output:\n{expected_out}\n\nActual output:\n{actual_out}")
+
 def main():
     GREEN = '\033[92m'
     RED = '\033[91m'