What Happened

Test script failed silently after first passing test. The script used set -e (exit on error) combined with bash arithmetic increment:

set -e
TESTS_PASSED=0

log_success() {
    echo "[PASS] $1"
    ((TESTS_PASSED++))  # THIS CAUSES EXIT!
}

Why It Matters

((TESTS_PASSED++)) returns exit code based on the POST-increment value:

• When TESTS_PASSED=0: ((0++)) evaluates to 0 (falsy) → exit code 1
• set -e sees exit code 1 → script exits

This is a common bash gotcha that’s hard to debug because:

• No error message
• Happens on the FIRST success, not failure
• Looks like it should work

Resolution

Use explicit arithmetic assignment instead:

log_success() {
    echo "[PASS] $1"
    TESTS_PASSED=$((TESTS_PASSED + 1))  # Safe - always returns 0
}

Lesson

Never use ((var++)) with set -e. The increment operator’s return value is the pre-increment value, which is falsy when starting from 0.