wing test

[eladb]

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Feature Spec

A proposal for a very simple unit testing capability that can help us raise the bar on quality. At the moment, our tests are not executing inflight code.

You can use wing test in order to execute tests that are built into the application.

Each test is a cloud function with the word test in its identifier "test".

For example:

// hello.w
bring cloud;

let b = new cloud.Bucket();
let t = inflight (e: str) => {
  print("inside inflight");
  b.put("file.txt", "hello");
  assert(b.get("file.txt") == "hello");
  assert(b.list().at(0) == "file1.txt");
};

new cloud.Function(t) as "test";

Now, if I run this:

$ wing test hello.w
2023-01-12T21:01:56.899Z {"message":"inside inflight"}
2023-01-12T21:01:56.901Z {"message":"Put (key=file.txt).","status":"success"}
2023-01-12T21:01:56.902Z {"message":"Get (key=file.txt).","status":"success","result":"\"hello\""}
2023-01-12T21:01:56.902Z {"message":"List (prefix=null).","status":"success","result":"[\"file.txt\"]"}
2023-01-12T21:01:56.902Z {"message":"Invoke (payload=\"{}\").","status":"failure","error":{}}
Error: assertion failed: '((await (await b.list()).at(0)) === "file1.txt")'
    at evalmachine.<anonymous>:37:23
    at Handler.handle (evalmachine.<anonymous>:38:15)
    at async exports.handler (evalmachine.<anonymous>:12:10)
    at async Object.withTrace (/Users/eladb/code/wing2/libs/wingsdk/lib/testing/simulator.js:107:38)
    at async main (/Users/eladb/code/wing2/apps/wing/test.js:13:3)

I can write multiple tests by simply creating additional functions:

new cloud.Function(...) as "test:bla";
new cloud.Function(...) as "test:blue";

Use Cases

Unit tests that cover both preflight and inflight.

Preflight code is executed during compilation, and this allows executing inflight as well.

Implementation Notes

Here's a little script I wrote that runs the root/test function inside a simulator. It takes in a .wsim file.

const sdk = require('@winglang/wingsdk');

async function main() {
  const s = new sdk.testing.Simulator({ simfile: process.argv[2] });
  await s.start();

  const f = s.getResource("root/test");

  s.onTrace({ 
    callback: trace => console.error(trace.timestamp, JSON.stringify(trace.data)) 
  });

  await f.invoke({});
  console.log("success");
}

main().catch(e => {
  console.error(e);
  process.exit(1);
});

Component

Other

[eladb]

And naturally we need built in support for snapshot testing

https://blog.janestreet.com/the-joy-of-expect-tests

[Chriscbr]

wing test is now available - I've created a separate issue for tracking support for snapshot tests #1214 🙂