Chore: Introduce integration tests

[JamesHenry]

No description provided.

[not-an-aardvark]

LGTM, I just have a few minor questions.

[not-an-aardvark]

If I'm not mistaken, this could just be cwd: __dirname.

[JamesHenry]

Ah yeah, that used to be nested that's why there is the join there!

[not-an-aardvark]

I think it would be possible to just use eslint.Linter here:

const linter = new eslint.Linter();

linter.defineParser("typescript-eslint-parser", require("../../parser"));
linter.defineRules(rules);
const messages = linter.verify(
  code,
  {
    parser: 'typescript-eslint-parser',
    parserOptions: {
      ecmaVersion: 8,
      ecmaFeatures: {
        jsx: true,
        experimentalObjectRestSpread: true,
        globalReturn: true
      },
      sourceType: sourceType || "script"
    }
  },
  { filename: 'fake-filename.js' }
)

[JamesHenry]

Unless I am mistaken when using the Linter, it is not possible to use extends. Being able to write integration tests concisely using presets is important IMO.

[JamesHenry]

E.g.

typescript-eslint-parser/tests/integration/typescript.spec.js

Lines 9 to 27 in 9ae4baa

	it("should fundamentally work with `eslint:all`", () => {
	verifyAndAssertMessages(
	unpad(`
	"use strict";
	const foo: string = "bar";
	`),
	{},
	["2:7 'foo' is assigned a value but never used. no-unused-vars"],
	"script",
	{
	baseConfig: {
	extends: ["eslint:all"],
	rules: {
	"eol-last": "off"
	}
	}
	}
	);
	});

[not-an-aardvark]

You're correct that it's not possible to use extends with Linter, but it doesn't seem like extends is being used for any of these tests. Were you planning to add it?

(I don't mean to block the PR with this concern -- I'm just bringing it up in case you made a mistake.)

[JamesHenry]

The one I pasted in directly above, line 20?

[not-an-aardvark]

Oops, I missed that, sorry. (I hadn't realized that this function was also being used from other files.)

[JamesHenry]

Yeah I wasn't a huge fan of the huge single file used by babel-eslint so I extracted it and refactored it within a helper function.

Thanks for the review!

[not-an-aardvark]

Do we need to copy-paste babel-eslint's license here since the tests are from babel-eslint?

[JamesHenry]

Yes, definitely

[JamesHenry]

Done

[not-an-aardvark]

Should these commented tests be removed?

[JamesHenry]

Yeah probably, there are some that will definitely never be relevant, some that I was planning on digging into at some point... Would definitely be fine just getting rid of them though.

[JamesHenry]

I have cleaned up the babel-eslint tests somewhat (all the flow ones now gone, for example), but have left in some commented out tests as they will form a useful basis for the custom Referencer which will come in a follow up PR.