debian: Add autopkgtest for upstream unit and integration tests

Add cfv-upstream test script that runs:
- Unit tests (test.py --unit)
- Integration tests - internal (test.py -i)
- Integration tests - external process (test.py -e)

The test script provides a 'python' shim for upstream tests that use
environment.

This matches the test suite run in CI and addresses maintainer feedback
about running tests in autopkgtests.

Author: sarsolot

debian/tests/cfv-upstream

@@ -0,0 +1,29 @@
+#!/bin/sh
+exec 2>&1
+set -e
+set -x
+
+cd "$(dirname "$0")/../.."
+
+if [ ! -f test/test.py ]; then
+  echo "test/test.py not found; are we in the source tree root?" >&2
+  exit 1
+fi
+
+# Provide a "python" shim for upstream tests that invoke /usr/bin/env python.
+tmpbin=$(mktemp -d)
+trap 'rm -rf "$tmpbin"' EXIT
+ln -s "$(command -v python3)" "$tmpbin/python"
+export PATH="$tmpbin:$PATH"
+
+python3 -W error -bb test/test.py --unit --exit-early
+
+ulimit -n || true
+ulimit -n 4096 || true
+
+python3 -W error -bb test/test.py -i --exit-early
+
+ulimit -n || true
+ulimit -n 4096 || true
+
+python3 test/test.py -e --exit-early

debian/tests/control

@@ -1,2 +1,5 @@
 Tests: cfv
 Depends: @
+
+Tests: cfv-upstream
+Depends: @, python3, coreutils, cksfv