Testing this plugin

Running the tests

We use Jest test suites.

However, since we're using Yarn, simply running jest may not work.

To support npm modules, the actual command we use for our tests is this:

$ yarn node --experimental-vm-modules $(yarn bin jest)

Testing the main class

This is the code I used for one of the test suites:

test(
	'Bundles sass sources from import statements',
	async function testSASSImport() {
		await expect(new Promise((ok, fail) => {
			const plugin = new ESBuildSASSModulesPlugin();

			const dir = p.dirname(p.resolve(PATH_SAMPLE_SIMPLE_SCSS, '../../'));

			const fakeEsb =
				{ async onResolve(filter, fn) {
					const
						{ path: pathSCSS
						, namespace: namespaceSCSS
						} = await fn(
						{ path: PATH_SAMPLE_SIMPLE_SCSS
						, kind: 'import-statement'
						, importer: p.resolve(PATH_SAMPLE_SIMPLE_JS)
						, resolveDir: dir
						}
					);

					expect(pathSCSS).toBe(p.resolve(PATH_SAMPLE_SIMPLE_SCSS));
					expect(namespaceSCSS)
						.toBe(ESBuildSASSModulesPlugin.namespace);

					const
						{ path: pathSASS
						, namespace: namespaceSASS
						} = await fn(
						{ path: PATH_SAMPLE_SIMPLE_SASS
						, kind: 'import-statement'
						, importer: p.resolve(PATH_SAMPLE_SIMPLE_JS)
						}
					);

					expect(pathSASS).toBe(p.resolve(PATH_SAMPLE_SIMPLE_SASS));
					expect(namespaceSASS)
						.toBe(ESBuildSASSModulesPlugin.namespace);
				}
				, onLoad(filter, fn) {
					ok(fn);
				}
				, async resolve(path) {
					if(path === PATH_SAMPLE_SIMPLE_SCSS) {
						return { path: p.resolve(PATH_SAMPLE_SIMPLE_SCSS) };
					}

					if(path === PATH_SAMPLE_SIMPLE_SASS) {
						return { path: p.resolve(PATH_SAMPLE_SIMPLE_SASS) };
					}
				}
				};

			expect(() => plugin.setup(fakeEsb)).not.toThrow();
		})
		.then(chainTestSASSbuild(
			PATH_SAMPLE_SIMPLE_SCSS,
			PATH_SAMPLE_SIMPLE_SCSS_COMPILED
		))
		.then(chainTestSASSbuild(
			PATH_SAMPLE_SIMPLE_SASS,
			PATH_SAMPLE_SIMPLE_SASS_COMPILED
		))).resolves.toBeTruthy();
	}
);

Basically, I used a fake esbuild object to test the correctness of the main behavior.

Testing the index file

test(
	'Builds a simple program',
	async function testSimpleBuild() {
		await testBuild(
			buildSimple(),
			PATH_SAMPLE_SIMPLE_JS_COMPILED
		);
	}
);

The testBuild() will chain an esbuild result (in this case, returned from buildSimple()) to a check that compares the produced outfile with a known compiled file (PATH_SAMPLE_SIMPLE_JS_COMPILED, in this case).

The list of PATH constants is found in test/constants.js. You can find a set of useful utils for tests in test/utils.js