add README

Signed-off-by: Mohammed Al Sahaf <msaa1990@gmail.com>

caddytest/spec/README.md

@@ -0,0 +1,120 @@
+# Caddy spec tests
+
+End-to-end HTTP tests for Caddy handlers, written in
+[Hurl](https://hurl.dev/). Each test drives a real Caddy process via the
+admin API on `:2019`, runs requests against `:9080` / `:9443`, and asserts
+on status, headers, and body. The Go integration suite under
+[`caddytest/integration`](../integration/) covers scenarios that need Go logic;
+this directory covers everything that is just "HTTP in, HTTP out."
+
+## Layout
+
+```
+spec/
+├── README.md
+├── hurl_vars.properties      # Shared variables ({{indexed_root}}, etc.)
+└── http/
+    ├── <directive>/
+    │   ├── spec.hurl         # One spec per directive
+    │   └── assets/           # Optional fixtures (file_server, templates, …)
+    └── …
+```
+
+Each `spec.hurl` is self-contained: it `POST`s its own Caddyfile to
+`/load`, then issues the requests that validate the directive. Because
+`/load` replaces the entire config, blocks within a file don't interfere
+with each other.
+
+## Prerequisites
+
+- Hurl 7.x — `brew install hurl` on macOS, or the
+  [official install guide](https://hurl.dev/docs/installation.html).
+- A Caddy binary running with the admin API on `:2019`. For coverage,
+  build with `-cover`:
+  ```bash
+  cd cmd/caddy && go build -cover -tags nobadger,nopgx,nomysql -o caddy-coverage
+  ```
+
+## Running
+
+Start Caddy in one terminal:
+
+```bash
+mkdir -p /tmp/caddy-coverage
+GOCOVERDIR=/tmp/caddy-coverage ./cmd/caddy/caddy-coverage run
+```
+
+Run the suite from the repo root in another terminal:
+
+```bash
+hurl --test \
+     --variables-file caddytest/spec/hurl_vars.properties \
+     --retry 3 --retry-interval 500 \
+     caddytest/spec/http/**/spec.hurl
+```
+
+Run a single spec:
+
+```bash
+hurl --test \
+     --variables-file caddytest/spec/hurl_vars.properties \
+     caddytest/spec/http/file_server/spec.hurl
+```
+
+The CI workflow in [`.github/workflows/ci.yml`](../../.github/workflows/ci.yml) runs the same command.
+
+`--retry 3 --retry-interval 500` is a safety net for the brief window after every `POST /load` when the TLS app is being re-provisioned and may not yet have a cert for `localhost`. It only fires on failure; passing requests pay nothing.
+
+## Coverage
+
+After the suite finishes, stop the daemon and convert the binary
+coverage profile:
+
+```bash
+./cmd/caddy/caddy-coverage stop
+go tool covdata textfmt -i=/tmp/caddy-coverage -o coverage.out
+go tool cover -html=coverage.out          # browser view
+go tool cover -func=coverage.out | less   # per-function summary
+```
+
+Filter to a specific package:
+
+```bash
+go tool cover -func=coverage.out | grep modules/caddyhttp/fileserver
+```
+
+## Writing a spec
+
+1. Create `http/<directive>/spec.hurl`.
+2. For each scenario, write a `POST /load` with a minimal Caddyfile,
+   then the request(s) that exercise it.
+3. Use real assertions on observable state — status, headers, body,
+   side-effect files. Avoid placeholder configs (e.g. routing logs to
+   `discard`); they prove only that the directive parses, not that it
+   works.
+4. If the directive has visible side effects you can't read from the
+   response, expose them with a sidecar site. For example, the `log`
+   spec writes to `/tmp/caddy-log-spec/*.log` and adds a `:9081
+   file_server` block so a follow-up GET can assert on the log
+   contents.
+5. Add reusable fixture paths to
+   [`hurl_vars.properties`](hurl_vars.properties) instead of hard-coding
+   them.
+
+### Conventions
+
+- **Ports** — `9080` (HTTP), `9443` (HTTPS), `:9081` for sidecar
+  backends. Admin API is `:2019`. These are also what `--retry`
+  assumes.
+- **TLS** — always include `[Options]\ninsecure: true` on HTTPS
+  requests; the local CA is not trusted.
+- **Templating** — Hurl renders `{{name}}` as variable substitution. If
+  you need literal `{{` in a Caddyfile (e.g. a `templates` body), escape
+  it as `\{\{ ... \}\}`.
+
+## Resources
+
+- [Hurl manual](https://hurl.dev/docs/manual.html)
+- [Caddy admin API](https://caddyserver.com/docs/api)
+- [Caddyfile reference](https://caddyserver.com/docs/caddyfile)
+- [Go coverage tooling](https://go.dev/testing/coverage/)