diff --git a/tests/test_CheckManager.py b/tests/test_CheckManager.py
index fe4a7ee..82d6b11 100644
--- a/tests/test_CheckManager.py
+++ b/tests/test_CheckManager.py
@@ -1,4 +1,5 @@
 import pytest
+import ast
 import importlib
 import logging
 import time
@@ -172,6 +173,83 @@ def test_total_checks(api_only, debug_function, expected_total):
     assert cm.total_checks == expected_total
 
 
+def test_api_checks_only_use_approved_external_commands():
+    with open(script.__file__, "r") as source_file:
+        module = ast.parse(source_file.read())
+
+    functions = {
+        node.name: node
+        for node in module.body
+        if isinstance(node, ast.FunctionDef)
+    }
+    approved_api_boundaries = {"icurl"}
+    forbidden_calls = {"Connection", "run_cmd", "os.system", "os.popen"}
+    forbidden_prefixes = ("subprocess.", "pexpect.")
+
+    def get_call_name(node):
+        if isinstance(node, ast.Name):
+            return node.id
+        if isinstance(node, ast.Attribute):
+            parent = get_call_name(node.value)
+            return "{}.{}".format(parent, node.attr) if parent else node.attr
+        return ""
+
+    def is_literal_icurl_command(node):
+        if not isinstance(node, (ast.List, ast.Tuple)) or not node.elts:
+            return False
+        executable = node.elts[0]
+        return isinstance(executable, ast.Str) and executable.s == "icurl"
+
+    def is_literal_icurl_call(node, function):
+        if not get_call_name(node.func).startswith("subprocess.") or not node.args:
+            return False
+        command = node.args[0]
+        if is_literal_icurl_command(command):
+            return True
+        if not isinstance(command, ast.Name):
+            return False
+        return any(
+            isinstance(candidate, ast.Assign)
+            and any(
+                isinstance(target, ast.Name) and target.id == command.id
+                for target in candidate.targets
+            )
+            and is_literal_icurl_command(candidate.value)
+            for candidate in ast.walk(function)
+        )
+
+    def find_forbidden_calls(function_name, visited=None):
+        if visited is None:
+            visited = set()
+        if function_name in visited or function_name in approved_api_boundaries:
+            return set()
+        visited.add(function_name)
+
+        findings = set()
+        function = functions.get(function_name)
+        if function is None:
+            return findings
+        for node in ast.walk(function):
+            if not isinstance(node, ast.Call):
+                continue
+            call_name = get_call_name(node.func)
+            if (
+                call_name in forbidden_calls
+                or call_name.startswith(forbidden_prefixes)
+            ) and not is_literal_icurl_call(node, function):
+                findings.add(call_name)
+            elif call_name in functions:
+                findings.update(find_forbidden_calls(call_name, visited))
+        return findings
+
+    violations = {
+        check.__name__: sorted(find_forbidden_calls(check.__name__))
+        for check in CheckManager.api_checks
+        if find_forbidden_calls(check.__name__)
+    }
+    assert violations == {}
+
+
 def test_exception_in_initialize():
     """Exception in initialize is not captured by CheckManager.
     The exception should go up to the script's main() and abort the script