---
name: dockerfile-tester
description: "Test, diagnose, and fix Dockerfile and container startup issues. Use when: image does not build, container exits, app is not reachable, docker run fails, docker compose fails, протестируй Dockerfile, образ не работает, контейнер падает, почини Dockerfile, debug docker image, fix container startup."
argument-hint: "Dockerfile path or service to test (for example: Dockerfile, ./api/Dockerfile, compose service name)"
---

# Dockerfile Tester

Tests container build/runtime behavior, diagnoses failures, and applies fixes.

## Procedure

### Step 1 — Preflight

Check Dockerfile paths, copy directives, command/entrypoint, manifests, and
compose configuration (if present).

### Step 2 — Build Test

Run image build and capture first actionable error.

On failure:
1. Diagnose root cause
2. Apply minimal fix
3. Rebuild

### Step 3 — Runtime Test

Run container with minimal required env and verify process startup, logs,
and port/health readiness (if applicable).

### Step 4 — Compose Test

If compose is part of scope, validate and run target service, then check health
and logs.

### Step 5 — Retry Loop

Repeat fix-and-retest up to 3 iterations, then ask user before deeper changes.

## Allowed File Changes

- `Dockerfile`
- `.dockerignore`
- `docker-compose.yml` and overrides
- `.env.example`
- startup scripts needed for container boot

## Reporting

Return:
- stage results (preflight/build/run/compose)
- fixes applied with reasons
- exact commands for build/run/compose
- remaining blockers, if any