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Tutorial

Learn WebSocket testing

Most API tests send a request and check the answer. A WebSocket doesn't work that way. The connection stays open, messages arrive when the server decides to send them, and the most common bugs happen when the connection ends rather than while it's working.

These lessons assume you know what an HTTP request is. If not, start with the API testing tutorial. Every example connects to the two sockets at wss://api.testingapis.com: one echoes what you send, one pushes a stock price every second. The messages and close codes shown are the ones they actually sent, and most lessons let you open the socket from the page. Both sockets need a free account; the examples and Connect buttons work once you're signed in.

8 lessons3 levelsFree

Beginner

3 lessons

What a WebSocket is, how one opens, and how messages travel in both directions.

  1. 01What a WebSocket isA connection that stays open, and either side can talk first.
  2. 02The opening handshakeHow an HTTP request becomes a socket, and the ways it fails before the first message.
  3. 03Sending and receiving messagesText, binary, JSON, size limits, and commands hidden in ordinary messages.

Intermediate

3 lessons

Streams the server pushes, how connections end, and what a client should do when one drops.

  1. 04Testing streams the server pushesSequence numbers, timing, the last message, and data that repeats.
  2. 05Closing and close codes1000, 1006, 1009 and the rest, and who gets the last word.
  3. 06Disconnects and reconnectingDetecting a dead connection, backing off, and not losing messages in the gap.

Advanced

2 lessons

Tests that wait for messages without guessing, and the security and load problems of long-lived connections.

  1. 07Automating WebSocket testsTurning events into something a test can wait for, with timeouts that fail clearly.
  2. 08Security and loadTokens without headers, origin checks, limits per connection, and testing thousands of sockets.