[test] Add assert_raises_process_error to assert process errors

test/functional/test_framework/util.py

@@ -14,6 +14,7 @@ import os
 import random
 import shutil
 import re
+from subprocess import CalledProcessError
 import time
 
 from . import coverage
@@ -59,6 +60,30 @@ def assert_raises_message(exc, message, fun, *args, **kwds):
     else:
         raise AssertionError("No exception raised")
 
+def assert_raises_process_error(returncode, output, fun, *args, **kwds):
+    """Execute a process and asserts the process return code and output.
+
+    Calls function `fun` with arguments `args` and `kwds`. Catches a CalledProcessError
+    and verifies that the return code and output are as expected. Throws AssertionError if
+    no CalledProcessError was raised or if the return code and output are not as expected.
+
+    Args:
+        returncode (int): the process return code.
+        output (string): [a substring of] the process output.
+        fun (function): the function to call. This should execute a process.
+        args*: positional arguments for the function.
+        kwds**: named arguments for the function.
+    """
+    try:
+        fun(*args, **kwds)
+    except CalledProcessError as e:
+        if returncode != e.returncode:
+            raise AssertionError("Unexpected returncode %i" % e.returncode)
+        if output not in e.output:
+            raise AssertionError("Expected substring not found:" + e.output)
+    else:
+        raise AssertionError("No exception raised")
+
 def assert_raises_jsonrpc(code, message, fun, *args, **kwds):
     """Run an RPC and verify that a specific JSONRPC exception code and message is raised.