API Automated Testing


npm install @ply-ct/ply --save-dev

Or, to run anywhere:

npm install -g @ply-ct/ply


Ply API testing starts with a YAML file containing requests. Here's a GET request to retrieve topics for the ply-demo repository using GitHub API v3:

  url: ''
  method: GET
    Accept: application/vnd.github.mercy-preview+json

Run a request

Suppose you save this in a file named "github.ply.yaml". Then you can submit the repositoryTopics request from a command line by typing:

ply -s github.ply.yaml

The -s argument tells Ply not to verify the response (-s is short for --submit, meaning submit an ad hoc request and don't bother with verification).

Verify response

If you run without -s you'll get an error saying, "Expected result file not found". Ply verification works by comparing expected vs actual. So a complete test requires an expected result file. Run again with --create, and the expected result file will be created from the actual response.

ply --create github.ply.yaml

Output looks like this:

Request 'repositoryTopics' submitted at 8/28/2020, 10:54:40:667
Creating expected result: ./results/expected/github.yaml
Test 'repositoryTopics' PASSED in 303 ms

During execution Ply submits the request and writes actual result file "./results/actual/github.yaml" based on the response. Because of --create, Ply then copies the actual result over expected result file "./results/expected/github.yaml" before comparing. This test naturally passes since the results are identical.

Expected results

Auto-creating an expected result provides a good starting point. But looking at "./results/expected/github.yaml", you'll notice that it includes many response headers that are not of interest for testing purposes. Here's a cleaned-up version of similar expected results from ply-demo:

    url: '${github.organization}/${github.repository}/topics'
    method: GET
      Accept: application/vnd.github.mercy-preview+json
      code: 200
      message: OK
      content-type: application/json; charset=utf-8
      status: 200 OK
    body: |-
        "names": [

The subset of response headers included in expected results YAML are those we care about for comparison. In this test, body content is our main concern.


Something else about this example that may be noticed by sharp-eyed observers: our request URL contains placeholders like ${github.organization}. Ply supports JavaScript template literal syntax for substituting dynamic values in both requests and results. Values come from JSON files and/or environment variables, as described in the docs under Values.

Even more powerfully, your multi-request suites can embed expressions that reference runtime values from previous responses. For instance, the URL or body of a subsequent request in our github.ply.yaml file could have something like this:


which uses the special @ character to reference the first topic name from above (resolving to 'rest-api'). This enables you to string together sequential requests that each depend on response output from preceding ones. Check out the Results topic for details and examples.


If you have Visual Studio Code with the Ply extension, you can graphically stitch together multiple requests into a workflow. See the Ply flows documentation for details.


For very complex testing scenarios, you'll want even greater control over request execution. Implement a Ply case suite using TypeScript for programmatic access to your requests/responses. Here's add new movie from ply-demo:

@test('add new movie')
async createMovie(values: any) {
    const result = await'createMovie', values);
    // capture movie id from response -- used in downstream values
    this.movieId = result.response?.body?.id;`Created movie: id=${this.movieId}`);

Applying the @test decorator to a method automatically makes it a Ply case. At this point this.requestSuite has already been loaded from request YAML (in the case suite's constructor):

this.requestSuite = ply.loadSuiteSync('test/requests/movies-api.ply.yaml');

Then in createMovie() above, the request named 'createMovie' from movies-api.ply.yaml is invoked by calling Ply's API method

Running a case suite from the command line is similar to running a request suite:

ply test/cases/movieCrud.ply.ts

This executes all cases in movieCrud.ply.ts (in the order they're declared), and compiles actual results from all requests into a file named after the @suite ("movie-crud.yaml"). At the end of the run, actual results are compared against expected to determine whether the suite has passed.


Body content in request YAML can be any text payload (typically JSON). GraphQL syntax is also supported, as in this example which queries the GitHub GraphQL API for ply-demo repository topics:

  url: ''
  method: POST
    Authorization: Bearer ${githubToken}
    Content-Type: application/json
    User-Agent: ${github.organization}
  body: |-
    query {
      repository(owner: "${github.organization}", name: "${github.repository}") {
        repositoryTopics(first: 10) {
          edges {
            node {
              topic {




Demo Project

VS Code Extension