tests: Add a script for find a minimal failing test sequence

min-seq.py can be used to find a minimal test sequence that can be used
to reproduce test failures. This is meant for being able to process the
recently added "Failure sequence:" entries from parallel-vm.log to
reduce manual work needed to debug commonly failing test case sequences.

Signed-off-by: Jouni Malinen <quic_jouni@quicinc.com>

diff --git a/tests/hwsim/vm/min-seq.py b/tests/hwsim/vm/min-seq.py
new file mode 100755 (executable)
index 0000000..a0fcc38
--- /dev/null
+++ b/tests/hwsim/vm/min-seq.py
@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+#
+# Minimal failing test sequence finder
+# Copyright (c) 2022, Qualcomm Innovation Center, Inc.
+#
+# This software may be distributed under the terms of the BSD license.
+# See README for more details.
+
+import subprocess
+import sys
+from colorama import Fore, Style
+
+def red(s, bright=False):
+    tmp = Style.BRIGHT if bright else ''
+    return tmp + Fore.RED + s + Style.RESET_ALL
+
+def yellow(s, bright=False):
+    tmp = Style.BRIGHT if bright else ''
+    return tmp + Fore.YELLOW + s + Style.RESET_ALL
+
+def bright(s):
+    return Style.BRIGHT + s + Style.RESET_ALL
+
+def run_tests(tests):
+    print(yellow("Run test sequence: ") + ' '.join(tests))
+    arg = ['./vm-run.sh'] + tests
+    cmd = subprocess.Popen(arg, stdout=subprocess.PIPE)
+    out = cmd.stdout.read().decode()
+    found = False
+    for i in out.splitlines():
+        if i.startswith('FAIL '):
+            t = i.split(' ')[1]
+            if t == tests[-1]:
+                found = True
+            else:
+                print(red("Unexpected FAIL: ", bright=True) + t)
+                return None
+    return found
+
+def reduce(tests):
+    if len(tests) < 2:
+        return None
+
+    # Try to remove first half of the test cases to speed up the initial process
+    if len(tests) > 10:
+        a = list(tests[int(len(tests) / 2):])
+        res = run_tests(a)
+        if res is None:
+            return None
+        if res:
+            return a
+
+    # Try to remove test cases one-by-one (starting with larger groups to speed
+    # up)
+    for count in [27, 9, 6, 3, 1]:
+        for i in range(0, len(tests) - count, count):
+            b = list(tests)
+            del b[i:i + count]
+            if len(b) < 2:
+                continue
+            res = run_tests(b)
+            if res is None:
+                return None
+            if res:
+                return b
+
+    return None
+
+def main():
+    tests = sys.argv[1:]
+    num_tests = len(tests)
+    if not run_tests(tests):
+        print(red("Full test sequence did not result in an error", bright=True))
+        return
+    while True:
+        new_tests = reduce(tests)
+        if (not new_tests) or len(new_tests) == len(tests):
+            break
+        tests = new_tests
+        print(yellow("Found a shorter sequence: ", bright=True) + ' '.join(tests))
+    if len(tests) < num_tests:
+        print(bright("Minimal sequence:"))
+        print(' '.join(tests))
+    else:
+        print(yellow("Could not remove any test cases without losing the failure"))
+
+if __name__ == "__main__":
+    main()