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diff --git a/scripts/test-zfs-snap-prune.sh b/scripts/test-zfs-snap-prune.sh
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+#!/bin/bash
+# test-zfs-snap-prune.sh - Comprehensive test suite for zfs-snap-prune
+#
+# Runs various scenarios with mock data to verify the pruning logic.
+# No root or ZFS required - uses --test mode with mock data.
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PRUNE_SCRIPT="$SCRIPT_DIR/../custom/zfs-snap-prune"
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+NC='\033[0m'
+
+# Test counters - use temp files to avoid subshell issues with pipes
+COUNTER_FILE=$(mktemp)
+echo "0 0 0" > "$COUNTER_FILE"  # run passed failed
+trap "rm -f $COUNTER_FILE" EXIT
+
+# Time constants for generating test data
+DAY=$((24 * 60 * 60))
+NOW=$(date +%s)
+
+# Generate a snapshot line for mock data
+# Args: snapshot_name days_ago
+# Output: zroot/ROOT/default@name<TAB>epoch_timestamp
+make_snap() {
+    local name="$1"
+    local days_ago="$2"
+    local timestamp=$((NOW - (days_ago * DAY)))
+    echo -e "zroot/ROOT/default@${name}\t${timestamp}"
+}
+
+# Generate N snapshots with given prefix and starting age
+# Args: prefix count start_days_ago
+# NOTE: Outputs oldest first (like ZFS with -s creation), so start_age is the OLDEST
+make_snaps() {
+    local prefix="$1"
+    local count="$2"
+    local start_age="$3"
+    # Generate from oldest to newest (ZFS order with -s creation)
+    for ((i=count; i>=1; i--)); do
+        make_snap "${prefix}_${i}" $((start_age + i - 1))
+    done
+}
+
+# Increment counter in temp file
+# Args: position (1=run, 2=passed, 3=failed)
+inc_counter() {
+    local pos="$1"
+    local counters
+    read -r run passed failed < "$COUNTER_FILE"
+    case "$pos" in
+        1) run=$((run + 1)) ;;
+        2) passed=$((passed + 1)) ;;
+        3) failed=$((failed + 1)) ;;
+    esac
+    echo "$run $passed $failed" > "$COUNTER_FILE"
+}
+
+# Get counter values
+get_counters() {
+    cat "$COUNTER_FILE"
+}
+
+# Run a test case
+# Args: test_name expected_kept expected_deleted env_vars
+# Reads mock snapshot data from stdin
+run_test() {
+    local test_name="$1"
+    local expected_kept="$2"
+    local expected_deleted="$3"
+    shift 3
+    local env_vars="$*"
+
+    inc_counter 1  # TESTS_RUN++
+    echo -e "${BLUE}TEST:${NC} $test_name"
+
+    # Capture stdin (mock data) and pass to prune script
+    local mock_data
+    mock_data=$(cat)
+
+    # Run prune script with mock data on stdin
+    local output
+    output=$(echo "$mock_data" | env NOW_OVERRIDE="$NOW" $env_vars "$PRUNE_SCRIPT" --test --quiet 2>&1)
+
+    # Extract results
+    local result_line
+    result_line=$(echo "$output" | grep "^RESULT:" || echo "RESULT:kept=0,deleted=0")
+    local actual_kept
+    actual_kept=$(echo "$result_line" | sed 's/.*kept=\([0-9]*\).*/\1/')
+    local actual_deleted
+    actual_deleted=$(echo "$result_line" | sed 's/.*deleted=\([0-9]*\).*/\1/')
+
+    # Compare
+    if [[ "$actual_kept" == "$expected_kept" ]] && [[ "$actual_deleted" == "$expected_deleted" ]]; then
+        echo -e "  ${GREEN}PASS${NC} (kept=$actual_kept, deleted=$actual_deleted)"
+        inc_counter 2  # TESTS_PASSED++
+        return 0
+    else
+        echo -e "  ${RED}FAIL${NC}"
+        echo -e "    Expected: kept=$expected_kept, deleted=$expected_deleted"
+        echo -e "    Actual:   kept=$actual_kept, deleted=$actual_deleted"
+        inc_counter 3  # TESTS_FAILED++
+        return 1
+    fi
+}
+
+# Print section header
+section() {
+    echo ""
+    echo -e "${YELLOW}=== $1 ===${NC}"
+}
+
+# Verify prune script exists
+if [[ ! -x "$PRUNE_SCRIPT" ]]; then
+    chmod +x "$PRUNE_SCRIPT"
+fi
+
+echo -e "${GREEN}zfs-snap-prune Test Suite${NC}"
+echo "========================="
+echo "Using NOW=$NOW ($(date -d "@$NOW" '+%Y-%m-%d %H:%M:%S'))"
+echo "Default policy: KEEP_COUNT=20, MAX_AGE_DAYS=180"
+
+###############################################################################
+section "Basic Cases"
+###############################################################################
+
+# Test 1: Empty list
+echo -n "" | run_test "Empty snapshot list" 0 0
+
+# Test 2: Single snapshot
+make_snap "test1" 5 | run_test "Single snapshot (recent)" 1 0
+
+# Test 3: Under keep count - all recent
+make_snaps "recent" 10 1 | run_test "10 snapshots, all recent" 10 0
+
+# Test 4: Exactly at keep count
+make_snaps "exact" 20 1 | run_test "Exactly 20 snapshots" 20 0
+
+###############################################################################
+section "Over Keep Count - Age Matters"
+###############################################################################
+
+# Test 5: 25 snapshots, all recent (within 180 days)
+# Should keep all - none old enough to delete
+make_snaps "recent" 25 1 | run_test "25 snapshots, all recent (<180 days)" 25 0
+
+# Test 6: 25 snapshots, 5 are old (>180 days)
+# First 20 (most recent) kept by count, 5 oldest are >180 days old, so deleted
+{
+    make_snaps "old" 5 200      # oldest first (200-204 days ago)
+    make_snaps "recent" 20 1    # newest last (1-20 days ago)
+} | run_test "25 snapshots, 5 old (>180 days) - delete 5" 20 5
+
+# Test 7: 30 snapshots, 10 beyond limit but only 5 old enough
+{
+    make_snaps "old" 5 200      # 200-204 days old - delete these
+    make_snaps "medium" 5 100   # 100-104 days old - not old enough
+    make_snaps "recent" 20 1    # 1-20 days old
+} | run_test "30 snapshots, 5 medium age, 5 old - delete 5" 25 5
+
+###############################################################################
+section "Genesis Protection"
+###############################################################################
+
+# Test 8: Genesis at position 21, old - should NOT be deleted
+{
+    make_snap "genesis" 365    # oldest: 1 year old
+    make_snaps "recent" 20 1   # newest: 1-20 days ago
+} | run_test "Genesis at position 21 (old) - protected" 21 0
+
+# Test 9: Genesis at position 25, with other old snapshots
+{
+    make_snap "genesis" 365    # oldest: protected
+    make_snaps "old" 4 200     # 200-203 days old - should be deleted
+    make_snaps "recent" 20 1   # 1-20 days old
+} | run_test "Genesis at position 25 with 4 old - delete 4, keep genesis" 21 4
+
+# Test 10: Genesis within keep count (20 total snapshots)
+{
+    make_snap "genesis" 365     # oldest
+    make_snaps "more" 9 15      # 15-23 days ago
+    make_snaps "recent" 10 1    # 1-10 days ago
+} | run_test "Genesis at position 11 (within keep count)" 20 0
+
+###############################################################################
+section "Custom Configuration"
+###############################################################################
+
+# Test 11: Custom KEEP_COUNT=5
+make_snaps "test" 10 200 | \
+    run_test "KEEP_COUNT=5, 10 old snapshots - delete 5" 5 5 KEEP_COUNT=5
+
+# Test 12: Custom MAX_AGE_DAYS=30
+{
+    make_snaps "medium" 5 50   # 50-54 days old - now considered old with MAX_AGE=30
+    make_snaps "recent" 20 1   # 1-20 days ago
+} | run_test "MAX_AGE_DAYS=30, 5 snapshots >30 days - delete 5" 20 5 MAX_AGE_DAYS=30
+
+# Test 13: Very short retention
+make_snaps "test" 15 10 | \
+    run_test "KEEP_COUNT=3, MAX_AGE=7, 15 snaps (10+ days old) - delete 12" 3 12 KEEP_COUNT=3 MAX_AGE_DAYS=7
+
+# Test 14: Relaxed retention - nothing deleted
+make_snaps "test" 50 1 | \
+    run_test "KEEP_COUNT=100 - keep all 50" 50 0 KEEP_COUNT=100
+
+###############################################################################
+section "Edge Cases"
+###############################################################################
+
+# Test 15: Snapshot exactly at MAX_AGE boundary (180 days) - should be kept
+{
+    make_snap "boundary" 180     # Exactly 180 days - >= cutoff, kept
+    make_snaps "recent" 20 1     # 1-20 days ago
+} | run_test "1 snapshot exactly at 180 day boundary - keep" 21 0
+
+# Test 16: Snapshot just over MAX_AGE boundary (181 days) - should be deleted
+{
+    make_snap "over" 181        # 181 days - just over, should be deleted
+    make_snaps "recent" 20 1    # 1-20 days ago
+} | run_test "1 snapshot at 181 days - delete" 20 1
+
+# Test 17: Mixed boundary - some at 180, some at 181
+{
+    make_snap "over2" 182       # deleted
+    make_snap "over1" 181       # deleted
+    make_snap "boundary" 180    # kept (exactly at cutoff)
+    make_snaps "recent" 20 1    # 1-20 days ago
+} | run_test "2 over boundary, 1 at boundary - delete 2" 21 2
+
+# Test 18: Mixed naming patterns (ordered oldest to newest)
+{
+    make_snap "genesis" 365
+    make_snap "before-upgrade" 20
+    make_snap "manual_backup" 15
+    make_snap "pre-pacman_2025-01-10" 10
+    make_snap "pre-pacman_2025-01-15" 5
+} | run_test "Mixed snapshot names (5 total)" 5 0
+
+# Test 19: Large number of snapshots
+{
+    make_snaps "old" 100 200   # 200-299 days old
+    make_snaps "recent" 20 1   # 1-20 days ago
+} | run_test "120 snapshots, 100 old - delete 100" 20 100
+
+###############################################################################
+section "Realistic Scenarios"
+###############################################################################
+
+# Test 20: One year of weekly pacman updates + genesis
+# 52 snapshots (one per week) + genesis
+# Ordered oldest first: genesis (365 days), then week_51 (357 days), ..., week_0 (0 days)
+{
+    make_snap "genesis" 365
+    for ((week=51; week>=0; week--)); do
+        make_snap "pre-pacman_week_${week}" $((week * 7))
+    done
+} | run_test "1 year of weekly updates (52) + genesis" 27 26
+# Analysis (after tac, newest first):
+# Position 1-20: week_0 through week_19 (0-133 days) - kept by count
+# Position 21-26: week_20 through week_25 (140-175 days) - kept by age (<180)
+# Position 27-52: week_26 through week_51 (182-357 days) - deleted (>180)
+# Position 53: genesis (365 days) - protected
+# Kept: 20 + 6 + 1 = 27, Deleted: 26
+
+# Test 21: Fresh install with only genesis
+make_snap "genesis" 1 | run_test "Fresh install - only genesis" 1 0
+
+# Test 22: Burst of manual snapshots before big change
+{
+    make_snap "genesis" 30
+    make_snap "before-nvidia" 20
+    make_snap "before-DE-change" 19
+    make_snaps "pre-pacman" 18 1
+} | run_test "20 snaps + genesis (30 days old)" 21 0
+
+###############################################################################
+section "Results"
+###############################################################################
+
+# Read final counters
+read -r TESTS_RUN TESTS_PASSED TESTS_FAILED < "$COUNTER_FILE"
+
+echo ""
+echo "========================="
+echo -e "Tests run:    $TESTS_RUN"
+echo -e "Tests passed: ${GREEN}$TESTS_PASSED${NC}"
+echo -e "Tests failed: ${RED}$TESTS_FAILED${NC}"
+echo ""
+
+if [[ $TESTS_FAILED -eq 0 ]]; then
+    echo -e "${GREEN}All tests passed!${NC}"
+    exit 0
+else
+    echo -e "${RED}Some tests failed.${NC}"
+    exit 1
+fi