[BUG] Error when running with Docker

[Jonny Morley]

Checklist

• I checked the FAQ section of the documentation
• I looked for similar issues in the issue tracker
• I am using the latest version of Schemathesis

Describe the bug

Schemathesis run via Docker won't connect to my locally running application.

To Reproduce

1. Create a dummy server file - app.js

const http = require("http")

const server = http.createServer((req, res) => {
  if (req.method === "GET") {
    if (req.url === "/cats") {
      res.writeHead(200, { "Content-Type": "application/json" })
      res.end(JSON.stringify({ message: "Hello" }))
    }
  }
})

const PORT = 3003

server.listen(PORT, () => {
  console.log(`Server is running on port ${PORT}`)
})

2. Create a dummy OpenAPI specification - cats-swagger.yml

openapi: 3.0.0
info:
  title: Simple JSON API
  version: 1.0.0
paths:
  /cats:
    get:
      summary: Get a friendly greeting
      responses:
        '200':
          description: Successful response
          content:
            application/json:
              schema:
                type: object
                properties:
                  message:
                    type: string
                    example: Hello

3. Run the server - node app.js

4. Run schemathesis via Docker

docker run --platform linux/amd64 --network host -v $(pwd)/cats-swagger.yml:/mnt/cats-swagger.yml schemathesis/schemathesis:latest run --hypothesis-max-examples=1 --base-url http://0.0.0.0:3003 /mnt/cats-swagger.yml

(I've tried against localhost and 127.0.0.1 also)

5. Observe the error

======================= Schemathesis test session starts =======================
Schema location: file:///mnt/cats-swagger.yml
Base URL: http://0.0.0.0:3003
Specification version: Open API 3.0.0
Workers: 1
Collected API operations: 1

GET /cats E                                                               [100%]

==================================== ERRORS ====================================
__________________________________ GET /cats ___________________________________
Network Error

Connection failed

    Failed to establish a new connection: [Errno 111] Connection refused

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=================================== SUMMARY ====================================

No checks were performed.

Hint: You can visualize test results in Schemathesis.io by using `--report` in your CLI command.

Expected behavior

No network errors

Environment

- OS: MacOS (Apple M1 Pro)
- Python version: N/A
- Schemathesis version: Latest
- Spec version: Open API 3.0.0

Tested on both Work and Home laptop (same specs)

Additional context

Include any other relevant details, like logs or screenshots.

[Dmitry Dygalo]

Hi @morley92

Hm, seems to be MacOS-specific, as it seems to work on my Linux machine but fails on my laptop. I'll take a closer look in the next following days.

[Dmitry Dygalo]

Using host.docker.internal:

docker run --platform linux/amd64 -v $(pwd)/cats-swagger.yml:/mnt/cats-swagger.yml schemathesis/schem
athesis:latest run --hypothesis-max-examples=1 --base-url http://host.docker.internal:3003 /mnt/cats-swagger.yml

======================= Schemathesis test session starts =======================
Schema location: file:///mnt/cats-swagger.yml
Base URL: http://host.docker.internal:3003
Specification version: Open API 3.0.0
Workers: 1
Collected API operations: 1

GET /cats .                                                               [100%]

=================================== SUMMARY ====================================

Performed checks:
    not_a_server_error                    1 / 1 passed          PASSED 

Tip: Use the `--report` CLI option to visualize test results via Schemathesis.io.
We run additional conformance checks on reports from public repos.

============================== 1 passed in 0.02s ===============================

Here is the relevant section from Docker for Mac docs:

The host has a changing IP address, or none if you have no network access. We recommend that you connect to the special DNS name host.docker.internal, which resolves to the internal IP address used by the host.

I'll update the docs to mention this.

[Jonny Morley]

thankyou!