babel-utils/babel-plugin-tester

Utilities for testing babel plugins

babel-plugin-tester's Issues

Upgrading from 5.x to 7.x produces different snapshots

• babel-plugin-tester version: 7.0.1
• node version: 10.16.3
• npm (or yarn) version: 1.12.1

Relevant code or config

https://github.com/necolas/react-native-web/blob/master/packages/babel-plugin-react-native-web/src/__tests__/index-test.js

What you did:

Updated babel-plugin-tester from 5 to 7

What happened:

All the snapshots broke because the output is now being compiled to ES5 code

    - const ReactNative = require('react-native-web/dist/index');
    + "use strict";
    +
    + var ReactNative = require("react-native-web/dist/index");

    - const unstable_createElement = require('react-native-web/dist/exports/createElement').default;
    + var unstable_createElement = require("react-native-web/dist/exports/createElement").default;

    - const ColorPropType = require('react-native-web/dist/exports/ColorPropType').default;
    + var ColorPropType = require("react-native-web/dist/exports/ColorPropType").default;

    - const StyleSheet = require('react-native-web/dist/exports/StyleSheet').default;
    + var StyleSheet = require("react-native-web/dist/exports/StyleSheet").default;

    - const View = require('react-native-web/dist/exports/View').default;
    + var View = require("react-native-web/dist/exports/View").default;

    - const TouchableOpacity = require('react-native-web/dist/exports/TouchableOpacity').default;
    + var TouchableOpacity = require("react-native-web/dist/exports/TouchableOpacity").default;

    - const processColor = require('react-native-web/dist/exports/processColor').default;
    + var processColor = require("react-native-web/dist/exports/processColor").default;

Reproduction repository:

https://github.com/necolas/react-native-web/

Problem description:

I want the snapshots not to change to compiled output

Issue with Babel `declare(...)` Api-Check Helper

• babel-plugin-tester version: 7.8.3
• node version: v12.14.0
• npm (or yarn) version: [email protected]

---

When using the declare(...) helper from @babel/helper-plugin-utils, the api.assertVersion(...) call gives me the following error:

  ● Test suite failed to run

    Requires Babel "^7.0.0-beta.41", but was loaded with "7.8.4". You'll need to update your @babel/core version.

      18 | export default declare((api, options, dirname) => {
      19 |   // check babel version
    > 20 |   api.assertVersion(7);

If you look at the error message, my @babel/core version is ahead of the minimum requirement. I believe this is the result of some incompatibility between the declare(...) helper and this library.

This message is not displayed if I switch to running my tests with @babel/helper-plugin-test-runner.

Please let me know if there's any additional information I can provide you with.

Failed test doesn't show diff

• babel-plugin-tester version: 5.4.0
• node version: 9.8.0
• npm (or yarn) version: 5.6.0

Relevant code or config

const pluginTester = require('babel-plugin-tester')
const myPlugin = require('./plugin')

pluginTester({
  plugin: myPlugin,
  filename: __filename,
  tests: [{
    fixture: '__fixtures__/1/from.js',
    outputFixture: '__fixtures__/1/to.js'
  }],
  babelOptions: {
    babelrc: true
  }
})

What you did:
I ran jest using jest test.js and the test failed, like it should, but I was expecting the usual diff showing what it got and what it expected, but only the following output appeared. Am I doing something wrong or does it only show that message?

What happened:

 FAIL  ./test.js
  ast-transform
    ✕ 1. ast-transform (57ms)

  ● ast-transform › 1. ast-transform

    AssertionError [ERR_ASSERTION]: Output is incorrect.

      at tester (node_modules/babel-plugin-tester/dist/index.js:206:28)
      at Object.<anonymous> (node_modules/babel-plugin-tester/dist/index.js:114:13)
      at step (node_modules/babel-plugin-tester/dist/index.js:43:191)
      at node_modules/babel-plugin-tester/dist/index.js:43:361

Test Suites: 1 failed, 1 total
Tests:       1 failed, 1 total
Snapshots:   0 total
Time:        1.49s
Ran all test suites matching /test.js/i.

same files - no match

Hi. I am diving into a simple test. Despite the content match of both the input and output files, the test results do differ in content due to the presence of (invisible) dots as apparent from the img below. How can it be avoided?

ReferenceError: describe is not defined

• babel-plugin-tester version:^5.4.0
• node version:v8.5.0
• npm (or yarn) version:5.3.0

Relevant code or config

var codeStr = "var a = 1";
var pluginTester = require('babel-plugin-tester')
var plugin = require("../lib/index")

pluginTester({
  plugin: plugin,
  tests: [
    codeStr
  ]
})

What you did:

I just use pluginTester to test my plugin and error happened.Should I install some other plugin?

What happened:

Reproduction repository:

Problem description:

Suggested solution:

Support babel 7.

• babel-plugin-tester version: v5.0.0
• node version: N/a
• npm (or yarn) version: N/a

What you did:
Tried to parse typescript using babel 7.

What happened:
It would not parse typescript.

Problem description:
Basically this npm package imports babel-core, but it was renamed to @babel/core in babel 7.

Suggested solution:
Possibly create a branch for babel 7 that imports @babel/core instead of babel-core and publish an alpha/beta of a new major version on the next npm channel from this branch.

How to ignore space diff?

When I test my plugin width babel-plugin-tester, I found the output and expected were only have difference of space. Could you tell me how to ignore the diff caused by space? THX.

plugins from babelOptions are applied differently in fixtures vs tests

• babel-plugin-tester version: 9.0.1
• node version: 14.3.0
• npm (or yarn) version: 1.22.4

Relevant code or config

import pluginTester from 'babel-plugin-tester/pure';
import * as path from 'path';
import plugin from 'babel-plugin-macros';

pluginTester({
  plugin,
  babelOptions: {
    plugins: [
      [
        'babel-plugin-module-resolver',
        {
          alias: {
            '@material-ui/utils': path.resolve(__dirname, '../src'),
          },
        },
      ],
    ],
  },
  filename: __filename,
  fixtures: path.resolve(__dirname, './__fixtures__'),
  tests: [
    {
      title: 'can throw on missing error codes',
      error: /unknown: Missing error code for message 'missing'. Did you forget to run `yarn extract-errors` first?/,
      code: `
        import MuiError from '@material-ui/utils/MuiError.macro';

        throw new MuiError('missing');`,
      pluginOptions: {
        muiError: {
          missingError: 'throw',
        },
      },
    },
  ],
});

What you did:

• use babel-plugin-module-resolver in babelOptions.plugins

What happened:

• Tests in tests pass since babel-plugin-module-resolver is applied before the plugin.

• Tests in fixtures fail because babel-plugin-module-resolver is not applied before plugin

  error message

  /home/eps1lon/Development/projects/mui/fork/packages/material-ui-utils/test/__fixtures__/literal/code.js: Cannot find module '@material-ui/utils/MuiError.macro' from '/home/eps1lon/Development/projects/mui/fork/packages/material-ui-utils/test/__fixtures__/literal'
  

Reproduction repository:

1. clone (checkout this specific commit) https://github.com/eps1lon/material-ui/tree/1ceb45f2f8ec509885fd68285f2ad90f8f1a4e44
2. yarn
3. yarn cross-env NODE_ENV=test mocha packages/material-ui-utils/test/MuiError.macro.test.js --watch

Problem description: I want to write the test that mirror actual usage. For babel macros I would need to use a different import source than what is actually used.

Suggested solution:

1. Always apply babelOptions.plugins first
2. Always apply babelOptions.plugins last but add an option so that we can configure it (either flag "applyFirst" or custom merger function)

Testing non-plugins

It would be nice to be able to use this tool for things other than plugins easily.

Right now I do stuff like this:

import pluginTester from 'babel-plugin-tester';
import printAST from 'ast-pretty-print';
import lib from './';

const plugin = () => {
  return {
    name: 'test-plugin',
    visitor: {
      Program(path) {
        let result = lib(path);
        let printed = printAST(result);
        path.pushContainer(
          'body', 
          t.expressionStatement(t.templateLiteral([
            t.templateElement({ raw: printed }, true)
          ]))
        );
      },
    },
  };
};

babelTester({
  plugin,
  snapshot: true,
  tests: [...]
});

But it'd be nice if I could get something lower level where I can just call a function on a Babel File and the returned result would get printed via ast-pretty-print for snapshotting.

babelTester({
  name: 'util',
  snapshot: true,
  fn: file => {
    return lib(file.path);
  },
  tests: [...]
});

Question: How can I set the filename for the babel state for testing?

• babel-plugin-tester version: 10.1.0
• node version: v18.8.0
• npm (or yarn) version: 4.0.0-rc.13

Relevant code or config

import pluginTester from "babel-plugin-tester";
import { PluginPass } from "@babel/core";

pluginTester({
	plugin: babelPlugin,
        filename: 'testing.ts', // <-- doesn't seem to propagate to `state.filename` - it's probably not the right option for this I assume
	tests: [{ code: "'hello';" }],
});

const babelPlugin = function babelPlugin(): {
	visitor: Visitor<PluginPass>;
} {
	return {
		visitor: {
			Identifier(path, state) {
				console.log(state.filename);
                        }
                 }
        }
}

What you did:
I'm trying to test out how to use state.filename inside of a plugin and how I can set it in the test code.

What happened:
I'm getting an error since the state.filename variable is by default undefined and I have not found a way to add it via the test.

Problem description:
I've tried solving this by setting the filename option (not sure if that's the correct one) but it did not work. I have also thought about using one of the wrapper options (I'm not sure what they do so, so far no luck 😅)

Feature request - Plugin options in fixtures directory

When using fixtures it would be nice if it was possible to provide plugin options in a options.json file.
This would make it easier to test different features of a plugin, where different settings can be provided.

TypeError: pluginTester is not a function (on version 8.0.1)

• babel-plugin-tester version: 8.0.1
• node version: v12.14.1
• yarn version: 1.21.1

Relevant code or config

const pluginTester = require("babel-plugin-tester");

pluginTester({});

What you did:
Ran the jest.

What happened:

TypeError: pluginTester is not a function

Problem description:

  "devDependencies": {
    "babel-plugin-tester": "8.0.1",
    "jest": "^25.1.0",
    "prettier": "^1.19.1"
  }

and run jest
It fails with the error above. (all other non-babel tester tests are green)

If I return back to version 7 it works fine. Have no idea what is wrong TBH :)

If I try to return jest to version 23 and 24 from 25, result is still the same. So probably some wrong babel compilation of source code of version 8? Have no idea TBH.

Suggested solution:

¯\_(ツ)_/¯

Best way to test code paths that throw errors?

• babel-plugin-tester version: 9.0.1
• node version: 10.16.3
• npm (or yarn) version: [email protected]

What you did:

Wrote code in the plugin that will throw an error if it is reached

What happened:

Test fails without the code path that throws an error being able to be tested correctly

Reproduction repository:

N/A

Problem description: If your babel plugin can enter a code path where it throws an error, I'm unsure how to test that code path

Suggested solution: Unsure right now

Cannot load babel plugins before SUT using .babelrc in fixtures

I am struggling to test a case where another plugin is changing the resolveModuleSource babel option. It seems that on options merge, plugins from a fixture .babelrc file are appended after the tested plugin. See below.

• babel-plugin-tester version: 3.3.0
• node version: 8.2
• npm (or yarn) version: yarn 0.27.5

Relevant code or config (.babelrc from fixtures)

{
  "plugins": [["./custom_resolver.js", { "foo": "bar" }]]
}

What you did:

I created a test with the following option: babelOptions: { babelrc: true },

What happened:

The custom babel config was loaded, but plugins were added after the SUT, whereas I needed them to be loaded before the SUT.

Reproduction repository:

See real34/tmp-babel-plugin-inline-import-graphql-ast@29ee949

You can checkout the sample repo and run yarn test to reproduce the error. It should generate a snapshot file without any error (the error is due to plugins sort order, which causes https://github.com/real34/tmp-babel-plugin-inline-import-graphql-ast/blob/29ee949fb817615bd61553d01e55af11baf2d19f/index.js#L20 to not be executed with the correct module resolver)

Suggested solution:

It would be great to provide/document a way to create a .babelrc file where the plugin and its options could be inserted anywhere in the plugins definitions. Or at least how to configure plugins to be run before the SUT.

The simplest solution I can think of would be to prepend plugins definition in

babel-plugin-tester/src/index.js

Line 213 in 6085c16

plugins: [[plugin, pluginOptions]],

from a new option key (something like: babelPreviousPlugins for instance)... but it feels a bit hacky no?

Another solution for my use case would be to support .babelrc.js files (see babel/babel#4630), which may allow here to define a custom source resolver

Maybe format should also be executed on output file

• babel-plugin-tester version: 11.0.4
• node version: 19.5.0
• npm (or yarn) version: pnpm 7.26.0

Relevant code or config

pluginTester({
  plugin: babelPluginJsxAssetUrlImport,
  fixtures: path.join(__dirname, 'fixtures'),
  babelOptions: {
    plugins: ['@babel/plugin-syntax-jsx']
  }
});

Problem description:

I create a simple fixture, then tormented by semicolons and blank lines. like this:

In fact the two files are exactly the same

Suggested solution:

before run expect, maybe should format output file use prettier.

ReferenceError: describe is not defined

• babel-plugin-tester 5.0.0:
• node 8.7.0:
• npm 5.4.2:

Relevant code or config

const pluginTester = require('babel-plugin-tester');

// normally you would import this from your plugin module
function identifierReversePlugin() {
  return {
    name: 'identifier reverse',
    visitor: {
      Identifier(idPath) {
        idPath.node.name = idPath.node.name.split('').reverse().join('')
      },
    },
  }
}

pluginTester({
  plugin: identifierReversePlugin,
  snapshot: true,
  tests: [
    {code: '"hello";', snapshot: false},
    {
      code: 'var hello = "hi";',
      output: 'var olleh = "hi";',
    },
    `
      function sayHi(person) {
        return 'Hello ' + person + '!'
      }
      console.log(sayHi('Jenny'))
    `,
  ],
})

What you did:
Run the sample code from the docs

What happened:
Throws with:

  return describe(describeBlockTitle, function () {
  ^

ReferenceError: describe is not defined

Testing plugin metadata

It's possible to return metadata from the babel file transform result with a plugin. Is there a feature that can be used in the plugin tester to extract the metadata?

const babelFileResult = transform();
console.log('code', babelFileResult.code);
console.log('metadata, babelFileResult.metadata);

If not, would it be possible to have a feature that matches the returned metadata somehow?

This metadata can be set with a plugin and can return some useful information such as when the plugin is trying to extract some infomation from the source code while transforming it

Errors

It'd be nice if this util could capture errors

{
  title: 'test',
  code: 'code',
  // one of
  error: true,
  error: 'Expected Error Message',
  error: /test on error/,
  error: SyntaxError,
  error: err => /foo/.test(err) && err instanceof SyntaxError,
},
```'

Or:

```js
{
  title: 'test',
  code: 'code',
  snapshot: true,
  error: true,
},

Only/Skip

It'd be nice to be able to configure test.only or test.skip:

{
  title: 'not working yet',
  ...
  skip: true,
},

{
  title: 'currently focused on',
  ...
  only: true,
},

Using api.assertVersion() in plugin breaks this package.

• babel-plugin-tester version: 8.0.0, 8.0.1
• node version: 10.18.1
• npm (or yarn) version: 6.13.6 (npm)

---

Relevant code or config:

Dummy plugin using api.assertVersion.

const { declare } = require("@babel/helper-plugin-utils");
const plugin = declare(({ assertVersion }) => {
	assertVersion(7);
	return { name: "dummy-plugin" };
});

---

What you did:

Execute tests.

---

What happened:

Requires Babel "^7.0.0-beta.41", but was loaded with "7.7.2". You'll need to update your @babel/core version.

Attempting to infer the name of your plugin failed. Tried to invoke the plugin which threw the error.

---

Reproduction repository:

babel-plugin-remove-template-literals-whitespace

---

Problem description:

Issue lies in getPluginName method, which has exactly same issue as is mentioned here. This method instantiate provided plugin with exports of @babel/core obtained in pluginTester method.

As a hotfix, api.assertVersion method in passed babel reference can be overloaded with noop only in getPluginName method.

name = plugin(/* api = */ Object.assign({}, babel, { assertVersion: noop }), /* options = */ {}, /* dirname = */ "").name;

But still, a proper fix will be required.

---

Suggested solution:

Not sure.

The line feed on windows is failing the tests

Hello

I'm using babel-plugin-tester to test a Babel plugin I am working on. (Great tool BTW; thanks for sharing this.)

My tests were failing for no apparent reason. Then I realize that the following line of code was returning an error because of a difference with the line feed \r\n vs \n.

I fixed the problem by replacing the following line of code:

assert.equal(actual, output, 'actual output does not match output.js')

... with this ...

const normalizeNewline = require('normalize-newline');
assert.equal(normalizeNewline(actual), normalizeNewline(output), 'actual output does not match output.js')

regeneratorRuntime is not defined

since you're using async function here and didn't use babel-plugin-transform-runtime.

Maybe set the target of env preset to 6 or add transform-regenerator to blacklist?

[Request|Idea]: Improve assertion error on fixture

• babel-plugin-tester version:5.5.2
• node version: v8.11.2
• npm (or yarn) version: [email protected]

What you did:
I have a fixture setup with an input/output code file and the following test configuration.

What happened:
On error the messaging is very generic and doesn't clue into the failure.

Screenshot of fixture input/output error:

Screenshot of snapshot error:

Reproduction repository:
I don't have one at this point that is public.

Problem description:
Error is not descriptive doesn't help point the user to resolution.

Suggested solution:
I know that snapshots look better since that functionality is built into jest. I think we should be able to use similar logic to find the difference between the 2 files contents.

Version 11.x Discussion

Hello! After nearly two years, the 11.0.0 version of babel-plugin-tester has been released 🎉🎉, and with it comes a bevy of improvements bringing the project up to date with the latest and greatest in the JavaScript ecosystem:

• ESM support
• Windows and WSL support
• First-class support for fixtures alongside test objects
• Built-in TypeScript support (no need for external @types/babel-plugin-tester package)
• Explicit Vitest, node:test, and Jasmine support with documented examples
• Built-in debug support
• Support for executing the results of transformations
• Support for configuring tests via environment variables
• Support for setup and teardown functions that run in a consistent order
• Support for testing presets as well as plugins
• Support for custom plugin and preset run order
• And more!

To ensure as smooth an experience as possible, preserving backwards compatibility was a priority for this release. The vast majority of babel-plugin-tester users should be able to migrate to the latest version without incident. However, if you notice any BC-breaking changes or have any questions or suggestions, feel free to leave a comment here or, if you encounter a problem, open a new issue.

I'll keep this issue pinned until the next minor release. Happy testing!

Setting babelrc to true isn't picking up .babelrc

I'm having an issue when doing:

babelOptions: {
    // doesn't work
    babelrc: true
},

This results in an unexpected token error as my test is attempting to parse code that requires multiple babel presets to parse (its a react component). This can easily be fixed by supplying the presets directly in the test config, or by adding the extends option like so:

babelOptions: {
    // this works
    presets: ["es2015", "stage-0", "react"],
    // this works too
    extends: path.resolve(__dirname, '..', '.babelrc'),
},

I'm wondering if I'm missing something here in regards to preferred approach when using a .babelrc? Looking through the code I don't see any logic around the babelrc boolean so I am unsure as to the desired experience here.

I would be happy to PR a fix if this indeed a bug, or update the documentation if I'm just missing something here. Thanks for this tool, it's super useful 👍

Support a fixtures directory

per the babel contributing docs and the generator-babel-plugin fixtures (for example), I think it would be really handy to support a fixturesDirectory which would do basically this

Document how to test a preset

Problem description:

plugin and pluginName are plugin-centric.
I would like to test a preset which bundle a couple of plugins.

Suggested solution:

Could you please document how to do that (if it's possible)?

Seven PRs with various bugfixes and requested features

Hello!

First, thanks so much for this awesome package, it has saved me hours of dev time! I've been using it to develop a dozen little babel plugins that do various things for my projects, but I've run into some difficulties using it. My strategy has been to copy-paste some on-the-fly fixes between projects which is not ideal, so I went ahead and bundled these fixes/features together into my own babel-plugin-tester fork which my team and I have been using successfully for a little while.

Today, I feel confident enough to contribute these fixes back upstream and hopefully retire the fork. They are:

1. #88: fix plugin order application for fixtures
   • Fixes #74
2. #89: fix fixtureOutputExt being ignored in root options.json
3. #90: add support for only, skip, and title test options in fixtures
4. #91: add support for arbitrary run order of plugin under test
   • Implements #76
5. #92: bring back (lightweight) plugin name inference
   • Partially reverts #78
6. #93: fix README typos, update with latest features, verbiage improvements

Additional details are in each PR. With the exception of #91 (which relies on #88), each PR is self-contained and doesn't rely on merging the others, so they can be modified, rejected, or accepted as desired. I also submitted a PR that combines these other six PRs together since the octopus merge strategy can't do it effectively.

Thanks again for this package!

Async plugin support

• babel-plugin-tester version: 10.0.0
• node version: v14.7.0
• npm (or yarn) version: 1.22.10

Relevant code or config

What you did:
Write an asynchronous babel plugin.

What happened:
You appear to be using an async plugin/preset, but Babel has been called synchronously

Reproduction repository:

Problem description:
babel-plugin-tester doesn't support asynchronous plugins (introduced in 7.13.0) because it calls babel.transform synchronously here, and babel.transformSync here.

Suggested solution:
Check for the existence of babel.transformAsync and use that, or fallback to synchronous call to babel.trasnform. Happy to make a PR if this is an acceptable solution!

Including typescript in tests

Hi,

this is more a question than a bug report - I'm pretty sure I'm missing something fairly obvious.

I'm trying to write a babel plugin that analyses typescript files, so I was trying to write a simple test file that analyses some code and prints out the typescript definition.

import pluginTester from "babel-plugin-tester";

pluginTester({
  plugin: identifierReversePlugin,
  snapshot: true,
  tests: [
    {
      code: `
import React from 'react'

interface Test {
  name: string;
}

const User: React.FC<Test> = () => {
  return null;
}
`,
      snapshot: true,
    },
  ],
});

function identifierReversePlugin() {
  return {
    name: "analyse ts",
    visitor: {
      Identifier(idPath) {
        console.log(idPath);
      },
    },
  };
}

However, when I run the test it throws the error

SyntaxError: unknown: Unexpected reserved word 'interface'. (3:0)

      1 | import React from 'react'
      2 |
    > 3 | interface Test {
        | ^
      4 |   name: string;
      5 | }
      6 |

I've tried to google my way through it but whatever I try, the error persists.

Would love some pointers on getting this to run :)

Best

Suggestion: Fixture output file extension configuration.

• babel-plugin-tester version: ^9.1.0
• node version: v12.16.3
• yarn version: 1.19.1

folder structure (some files ommited):

ROOT
|-- package.json
|-- src
    |-- __tests__
    |   |-- __fixtures__
    |   |   |-- firstTest
    |   |   |     \-- code.ts
    |   |   \-- secondTest
    |   |         \-- code.ts
    |   \-- index-test.ts
    \-- index.ts

content of src/__tests__/index-test.ts file:

import pluginTester from "babel-plugin-tester";
import * as path from "path";

import plugin from ".."; // my babel plugin

pluginTester({
    plugin,
    pluginName: "plugin",
    endOfLine: "crlf",
    babelOptions: {
        presets: ["@babel/preset-env", "@babel/preset-typescript"],
        plugins: [
            "@babel/plugin-proposal-class-properties",
            "@babel/plugin-proposal-export-default-from",
            "@babel/proposal-object-rest-spread",
        ],
    },
    filename: __filename,
    fixtures: path.join(__dirname, '__fixtures__'),
});

What you did:
run jest via 'yarn test' command ("test": "jest" in package.json)

What happened:
test run succesfully and created files __fixtures__/*/output.ts

Problem description:
output files have .ts extension because source files are written in typescript, but theyre actually transpiled javascripts, so they should have .js extension.

Suggested solution:
add option to speicfy output file extension:
fixtureOutputExt?: string | (test: string) => string where:

• string: all output files use this extension
• (testName: string) => string: projection 'test name' to output extension: name => name === "firstTest" ? ".jsx" : ".js";

How to specify the ordering of the tested plugin

Hi.

I'm trying to write a babel plugin that transforms one decorator into a different one. For instance transform

class MyClass {
  @injectIfEnabled('FEATURE') router
}

into

class MyClass {
  @inject router
}

when that feature is enabled or into

class MyClass {
  @inject router
}

when it's not.

I'm running these:

• babel-plugin-tester 9.2.0:
• node 14:
• npm (or yarn) version: 6.14

The problem I'm facing is that since my plugin looks for class properties with a decorator named injectIfEnabled, I need the plugin to run before @babel/plugin-proposal-decorators has transpiled decorators.

I can't seem to find a way of specifying that the plugin under testing must run in a specific order:

pluginTester({
    plugin: myPlugin,
    pluginName: 'my-plugin',
    babelOptions: {
        plugins: [
          ['@babel/plugin-syntax-decorators', { legacy: true }],
          // myPlugin should run here
          ['@babel/plugin-proposal-class-properties', { loose: true }]
        ]
    },
})

Am I missing something or this is really not possible right now?