chore: add dockerfile.test + compose for running the spec suite in docker

Existing Dockerfile builds the production image with
BUNDLE_WITHOUT=development:test, so it can't run RSpec. This adds a
test-only image that ships every native lib the app loads at boot
(libvips, libpdfium, onnxruntime, chromium for cuprite) plus the full
dev/test gem bundle.

Usage:
  docker compose -f docker-compose.test.yml up --build
  # or run a subset:
  SPEC_FILES="spec/requests/well_known_spec.rb" \
    docker compose -f docker-compose.test.yml up --build --exit-code-from test

The bundle gems live in a named volume so `docker compose up` re-runs
are fast after the first build. Postgres uses tmpfs — no state
persists between runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Dockerfile.test

@@ -0,0 +1,70 @@
+# syntax=docker/dockerfile:1.7
+# Test-only image: runs the full Rails/RSpec suite with every native lib the
+# app loads at boot (libvips, libpdfium, onnxruntime, chromium for cuprite).
+# Source code is mounted at runtime via docker-compose.test.yml — only the
+# Gemfile is baked in so `bundle install` caches between runs.
+
+FROM ruby:4.0.1-alpine AS pdfium
+
+WORKDIR /download
+
+RUN apk --no-cache add wget && \
+    wget -O pdfium-linux.tgz "https://github.com/bblanchon/pdfium-binaries/releases/latest/download/pdfium-linux-musl-$(uname -m | sed 's/x86_64/x64/;s/aarch64/arm64/').tgz" && \
+    mkdir -p /pdfium-linux && \
+    tar -xzf pdfium-linux.tgz -C /pdfium-linux
+
+FROM ruby:4.0.1-alpine
+
+ENV RAILS_ENV=test \
+    BUNDLE_WITHOUT="" \
+    LANG=C.UTF-8 \
+    TZ=UTC
+
+WORKDIR /app
+
+# System deps:
+#   - libpq / libpq-dev  → pg gem
+#   - vips + vips-heif   → image processing (ruby-vips FFI)
+#   - onnxruntime        → field detection at boot
+#   - chromium + chromium-chromedriver → capybara/cuprite system specs
+#   - fontconfig + ttf-* → PDF rendering
+#   - build-base/git/yaml-dev → native gem compilation
+RUN apk add --no-cache \
+    build-base \
+    git \
+    bash \
+    curl \
+    yaml-dev \
+    libpq \
+    libpq-dev \
+    vips \
+    vips-dev \
+    vips-heif \
+    redis \
+    fontconfig \
+    ttf-dejavu \
+    onnxruntime \
+    nodejs \
+    yarn \
+    chromium \
+    chromium-chromedriver \
+    tzdata
+
+# libpdfium is not in Alpine packages — copy the prebuilt binary.
+COPY --from=pdfium /pdfium-linux/lib/libpdfium.so /usr/lib/libpdfium.so
+
+# Bundle deps. Copy only Gemfile/Gemfile.lock so this layer is cached while
+# source code changes beneath it.
+COPY Gemfile Gemfile.lock ./
+RUN bundle config set --local without "" && \
+    bundle install --jobs 4 --retry 3
+
+# Link onnxruntime.so into the onnxruntime gem's vendor dir (mirrors the
+# production Dockerfile) so the gem finds it at runtime.
+RUN ln -sf /usr/lib/libonnxruntime.so.1 \
+    "$(ruby -e "print Dir[Gem::Specification.find_by_name('onnxruntime').gem_dir + '/vendor/*.so'].first")"
+
+# Cuprite launches Chromium directly — point it at the Alpine binary.
+ENV CUPRITE_CHROME_PATH=/usr/bin/chromium-browser
+
+CMD ["bundle", "exec", "rspec"]

docker-compose.test.yml

@@ -0,0 +1,38 @@
+services:
+  test:
+    build:
+      context: .
+      dockerfile: Dockerfile.test
+    depends_on:
+      postgres:
+        condition: service_healthy
+    environment:
+      RAILS_ENV: test
+      DATABASE_URL: postgresql://postgres:postgres@postgres:5432/docuseal_test
+      # Silence bootsnap cache warnings when mounting source read-write.
+      BOOTSNAP_CACHE_DIR: /tmp/bootsnap
+    volumes:
+      - .:/app
+      - bundle:/usr/local/bundle
+    command: >
+      bash -c "
+        bin/rails db:prepare &&
+        bundle exec rspec ${SPEC_FILES:-spec}
+      "
+
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: postgres
+      POSTGRES_PASSWORD: postgres
+      POSTGRES_DB: docuseal_test
+    tmpfs:
+      - /var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U postgres"]
+      interval: 2s
+      timeout: 3s
+      retries: 10
+
+volumes:
+  bundle: