test: add unit tests for find_rpm_linux_srcdir

Simulate RPM BUILD directory layouts across distros to validate the
source extraction logic introduced in the previous commit:
- Flat layout (Fedora < 42, RHEL 9, aarch64 variant)
- Nested layout (Fedora 42+, aarch64 variant)
- configs/ directory exclusion
- Error cases: ambiguous matches, missing source, excessive depth

Signed-off-by: Or Shoval <oshoval@redhat.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

Author: oshoval

test/unit/test-fedora-source-nesting.sh

@@ -0,0 +1,69 @@
+#!/bin/bash
+# Test find_rpm_linux_srcdir() from kpatch-build.
+#
+# Verifies source directory detection across RPM BUILD layouts:
+#   Flat:   BUILD/kernel-6.12.0/linux-6.12.0-100.fc41.x86_64/         (Fedora <42, RHEL, CentOS)
+#   Nested: BUILD/kernel-6.14.0-build/kernel-6.14/linux-6.14.0-63.fc42.x86_64/  (Fedora 42+)
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")/../.." && pwd)"
+
+# Stub kpatch-build helpers so die doesn't exit and logger doesn't need a logfile.
+die()    { echo "die: $*" >&2; return 1; }
+logger() { cat >/dev/null; }
+
+source "$SCRIPT_DIR/kpatch-build/kpatch-funcs.sh"
+
+TESTDIR=$(mktemp -d)
+trap 'rm -rf "$TESTDIR"' EXIT
+ERRORS=0
+
+# Create a BUILD tree, run find_rpm_linux_srcdir, check result.
+#   $1 = test name
+#   $2 = expected: "ok" (source moved) or "fail" (die called)
+#   $3... = paths to create under BUILD/
+assert_layout() {
+	local name="$1" expect="$2"; shift 2
+	local dir="$TESTDIR/$name"
+	local rc=0
+
+	mkdir -p "$dir/BUILD" "$dir/dest"
+	for p in "$@"; do mkdir -p "$dir/BUILD/$p"; done
+
+	RPMTOPDIR="$dir" KERNEL_SRCDIR="$dir/dest/linux" \
+		find_rpm_linux_srcdir 2>/dev/null || rc=$?
+
+	case "$expect" in
+		ok)   [[ $rc -eq 0 && -d "$dir/dest/linux" ]] || { echo "FAIL  $name"; ((ERRORS++)); return; } ;;
+		fail) [[ $rc -ne 0 ]] || { echo "FAIL  $name — expected error"; ((ERRORS++)); return; } ;;
+	esac
+	echo "ok    $name"
+}
+
+# Flat layout: Fedora 41 / RHEL / CentOS
+assert_layout "flat-fc41-x86_64"   ok    "kernel-6.12.0/linux-6.12.0-100.fc41.x86_64"
+assert_layout "flat-fc41-aarch64"  ok    "kernel-6.12.0/linux-6.12.0-100.fc41.aarch64"
+assert_layout "flat-rhel9"         ok    "kernel-5.14.0/linux-5.14.0-362.el9.x86_64"
+
+# Nested layout: Fedora 42+
+assert_layout "nested-fc42"        ok    "kernel-6.14.0-build/kernel-6.14/linux-6.14.0-63.fc42.x86_64"
+assert_layout "nested-fc42-arm"    ok    "kernel-6.14.0-build/kernel-6.14/linux-6.14.0-63.fc42.aarch64"
+
+# configs/linux-* dirs must be ignored by the nested search
+assert_layout "nested-with-configs" ok   "kernel-6.14.0-build/configs/linux-extra" \
+                                         "kernel-6.14.0-build/kernel-6.14/linux-6.14.0-63.fc42.x86_64"
+
+# Error: ambiguous (multiple matches)
+assert_layout "multi-flat"         fail  "kernel-6.14.0/linux-6.14.0-aaa" \
+                                         "kernel-6.14.0/linux-6.14.0-bbb"
+assert_layout "multi-nested"       fail  "kernel-6.14.0-build/kernel-6.14/linux-aaa" \
+                                         "kernel-6.14.0-build/kernel-6.14/linux-bbb"
+
+# Error: nothing to find
+assert_layout "empty-build"        fail
+assert_layout "no-linux-dir"       fail  "kernel-6.14.0-build/kernel-6.14/sources"
+assert_layout "too-deep"           fail  "a/b/c/d/linux-6.14.0"
+
+echo ""
+[[ $ERRORS -gt 0 ]] && { echo "$ERRORS test(s) failed"; exit 1; }
+echo "All tests passed."