Tests

Winglang incorporates a lightweight testing framework, which is built around the wing test command and the test keyword. It lets you to run the same tests, in isolation, on both the Wing simulator and in the cloud.

How to create a test

You can create a test by adding the following code structure to any Winglang file (.w):

test "<test-name>" {
  // test code
}

If a test throws an exception (typically using the assert function), it's considered to have failed.

Here's an example:

// example.w
bring math;

test "abs" {
  assert(1 == math.abs(-1));
}

Running tests in the Simulator

You can execute all tests in a .w file in the simulator using the following command:

% wing test example.w --target sim
pass ─ example.wsim » root/env0/test:abs


Tests 1 passed (1)
Test Files 1 passed (1)
Duration 0m0.54s

Notice: The --target sim argument can be omitted as it's the default target for the wing test command.

Tests run in isolation

Every Winglang test is executed in complete isolation. Take a look at the following code:

bring cloud;

let b = new cloud.Bucket();

test "bucket list should include created file" {
  b.put("file", "lorem ipsum");
  let listOfFile = b.list();
  assert(listOfFile.length == 1);
}

test "bucket starts empty" {
  let listOfFile = b.list();
  assert(listOfFile.length == 0);
}

In the first test (bucket list should include created file), a file is created in the bucket. The second test (bucket starts empty) verifies that the bucket is initialized without any file.

Running tests in the cloud

Consider the following example:

bring cloud;
bring util;

let b = new cloud.Bucket();
b.onCreate(inflight (key: str) => {
  if !key.startsWith("/dest") {
    let content = b.get(key);
    b.put("/dest/" + key, content.uppercase());
  }
});

test "bucket onCreate" {
  b.put("file", "lorem ipsum");
  // Using waitUntil for waiting until the async event system of onCreate
  // finished generating a the dest/file
  let foundUppercaseFile = util.waitUntil((): bool => {
      return b.exists("/dest/file");
  });
  assert(foundUppercaseFile && b.get("/dest/file") == "LOREM IPSUM");
}

Running the test on the tf-aws target

% wing test example.w -t tf-aws
✔ Compiling example.w to tf-aws...
✔ terraform init
✔ terraform apply
✔ Setting up test runner...
✔ Running tests...
pass ─ example.tfaws » root/Default/env0/test:bucket onCreate
✔ terraform destroy


Tests 1 passed (1)
Test Files 1 passed (1)
Duration 1m31.44s

By default, the tested resources will be destroyed at the end of the test. You can use the --no-clean to keep them up. The path to the randomized directory containing the output files will be displayed at the end of the test.

% wing test example.w -t tf-aws --no-clean
✔ Compiling example.w to tf-aws...
✔ terraform init
✔ terraform apply
✔ Setting up test runner...
✔ Running tests...
pass ─ example.tfaws » root/Default/env0/test:bucket onCreate
✔ terraform destroy
Clean up is disabled!
Output files available at /var/folders/1m/..../example.tfaws

Tests 1 passed (1)
Test Files 1 passed (1)
Duration 1m31.44s

Running tests in the console

Wing Console provides a straightforward method to run either a single test or all your tests.

Consider the following code:

// example.w
bring cloud;

let b = new cloud.Bucket();

test "bucket list should include created file" {
  b.put("file", "lorem ipsum");
  let listOfFile = b.list();
  assert(listOfFile.length == 1);
}

test "bucket starts empty" {
  let listOfFile = b.list();
  assert(listOfFile.length == 0);
}

test "this test should fail" {
  throw "test throws an exception fails";
}

Refer to the TESTS section in the image below. You have the option to run all tests or a single test.

Saving test output to a file

To save test output to a file, add the relative path to the file to the -o or --output-file option. The format is inferred by the extension, only .json is supported at the moment.

For example: wing test -t sim -o out.json /test/file.test.w wing test -t sim --output-file path/to/out.json /test/file.test.w