diff --git a/test/browser/define.d.ts b/test/browser/define.d.ts
index 1e9efb55b8a..1fde8f77e5e 100644
--- a/test/browser/define.d.ts
+++ b/test/browser/define.d.ts
@@ -1,5 +1,5 @@
-import type { TestConfigBase } from '../types';
+import type { TestConfigBrowser } from '../types';
 
 declare global {
-	function defineTest(config: TestConfigBase): TestConfigBase;
+	function defineTest(config: TestConfigBrowser): TestConfigBrowser;
 }
diff --git a/test/browser/index.js b/test/browser/index.js
index f018571a648..2167a4210a9 100644
--- a/test/browser/index.js
+++ b/test/browser/index.js
@@ -13,58 +13,65 @@ const fixturify = require('fixturify');
 const { rollup } = require('../../browser/dist/rollup.browser.js');
 const { assertFilesAreEqual, runTestSuiteWithSamples, compareError } = require('../utils.js');
 
-runTestSuiteWithSamples('browser', resolve(__dirname, 'samples'), (directory, config) => {
-	(config.skip ? it.skip : config.solo ? it.only : it)(
-		basename(directory) + ': ' + config.description,
-		async () => {
-			let bundle;
-			try {
-				bundle = await rollup({
-					input: 'main',
-					onwarn: warning => {
-						if (!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))) {
-							throw new Error(
-								`Unexpected warnings (${warning.code}): ${warning.message}\n` +
-									'If you expect warnings, list their codes in config.expectedWarnings'
-							);
-						}
-					},
-					strictDeprecations: true,
-					...config.options
-				});
-			} catch (error) {
+runTestSuiteWithSamples(
+	'browser',
+	resolve(__dirname, 'samples'),
+	/**
+	 * @param {import('../types').TestConfigBrowser} config
+	 */
+	(directory, config) => {
+		(config.skip ? it.skip : config.solo ? it.only : it)(
+			basename(directory) + ': ' + config.description,
+			async () => {
+				let bundle;
+				try {
+					bundle = await rollup({
+						input: 'main',
+						onwarn: warning => {
+							if (!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))) {
+								throw new Error(
+									`Unexpected warnings (${warning.code}): ${warning.message}\n` +
+										'If you expect warnings, list their codes in config.expectedWarnings'
+								);
+							}
+						},
+						strictDeprecations: true,
+						...config.options
+					});
+				} catch (error) {
+					if (config.error) {
+						compareError(error, config.error);
+						return;
+					} else {
+						throw error;
+					}
+				}
 				if (config.error) {
-					compareError(error, config.error);
-					return;
-				} else {
-					throw error;
+					throw new Error('Expected an error while rolling up');
+				}
+				let output;
+				try {
+					({ output } = await bundle.generate({
+						exports: 'auto',
+						format: 'es',
+						...(config.options || {}).output
+					}));
+				} catch (error) {
+					if (config.generateError) {
+						compareError(error, config.generateError);
+						return;
+					} else {
+						throw error;
+					}
 				}
-			}
-			if (config.error) {
-				throw new Error('Expected an error while rolling up');
-			}
-			let output;
-			try {
-				({ output } = await bundle.generate({
-					exports: 'auto',
-					format: 'es',
-					...(config.options || {}).output
-				}));
-			} catch (error) {
 				if (config.generateError) {
-					compareError(error, config.generateError);
-					return;
-				} else {
-					throw error;
+					throw new Error('Expected an error while generating output');
 				}
+				assertOutputMatches(output, directory);
 			}
-			if (config.generateError) {
-				throw new Error('Expected an error while generating output');
-			}
-			assertOutputMatches(output, directory);
-		}
-	);
-});
+		);
+	}
+);
 
 function assertOutputMatches(output, directory) {
 	/** @type any */
diff --git a/test/chunking-form/index.js b/test/chunking-form/index.js
index f0dd86fcd40..d26628eef97 100644
--- a/test/chunking-form/index.js
+++ b/test/chunking-form/index.js
@@ -8,55 +8,64 @@ const { runTestSuiteWithSamples, assertDirectoriesAreEqual } = require('../utils
 
 const FORMATS = ['es', 'cjs', 'amd', 'system'];
 
-runTestSuiteWithSamples('chunking form', resolve(__dirname, 'samples'), (directory, config) => {
-	(config.skip ? describe.skip : config.solo ? describe.only : describe)(
-		basename(directory) + ': ' + config.description,
-		() => {
-			let bundle;
+runTestSuiteWithSamples(
+	'chunking form',
+	resolve(__dirname, 'samples'),
+	/**
+	 * @param {import('../types').TestConfigChunkingForm} config
+	 */
+	(directory, config) => {
+		(config.skip ? describe.skip : config.solo ? describe.only : describe)(
+			basename(directory) + ': ' + config.description,
+			async () => {
+				let bundle;
 
-			if (config.before) {
-				before(config.before);
-			}
-			if (config.after) {
-				after(config.after);
-			}
+				if (config.before) {
+					await before(config.before);
+				}
+				if (config.after) {
+					await after(config.after);
+				}
 
-			for (const format of FORMATS) {
-				it('generates ' + format, async () => {
-					chdir(directory);
-					bundle =
-						bundle ||
-						(await rollup({
-							input: [directory + '/main.js'],
-							onwarn: warning => {
-								if (!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))) {
-									throw new Error(
-										`Unexpected warnings (${warning.code}): ${warning.message}\n` +
-											'If you expect warnings, list their codes in config.expectedWarnings'
-									);
-								}
+				for (const format of FORMATS) {
+					it('generates ' + format, async () => {
+						chdir(directory);
+						bundle =
+							bundle ||
+							(await rollup({
+								input: [directory + '/main.js'],
+								onwarn: warning => {
+									if (
+										!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))
+									) {
+										throw new Error(
+											`Unexpected warnings (${warning.code}): ${warning.message}\n` +
+												'If you expect warnings, list their codes in config.expectedWarnings'
+										);
+									}
+								},
+								strictDeprecations: true,
+								...config.options
+							}));
+						await generateAndTestBundle(
+							bundle,
+							{
+								dir: `${directory}/_actual/${format}`,
+								exports: 'auto',
+								format,
+								chunkFileNames: 'generated-[name].js',
+								validate: true,
+								...(config.options || {}).output
 							},
-							strictDeprecations: true,
-							...config.options
-						}));
-					await generateAndTestBundle(
-						bundle,
-						{
-							dir: `${directory}/_actual/${format}`,
-							exports: 'auto',
-							format,
-							chunkFileNames: 'generated-[name].js',
-							validate: true,
-							...(config.options || {}).output
-						},
-						`${directory}/_expected/${format}`,
-						config
-					);
-				});
+							`${directory}/_expected/${format}`,
+							config
+						);
+					});
+				}
 			}
-		}
-	);
-});
+		);
+	}
+);
 
 async function generateAndTestBundle(bundle, outputOptions, expectedDirectory, config) {
 	await bundle.write({
diff --git a/test/chunking-form/samples/deprecated/empty-module-no-treeshake/_config.js b/test/chunking-form/samples/deprecated/empty-module-no-treeshake/_config.js
index 3fa8b308782..bd12a97ad57 100644
--- a/test/chunking-form/samples/deprecated/empty-module-no-treeshake/_config.js
+++ b/test/chunking-form/samples/deprecated/empty-module-no-treeshake/_config.js
@@ -1,5 +1,6 @@
 const assert = require('node:assert');
 const path = require('node:path');
+// @ts-expect-error not included in types
 const { getObject } = require('../../../../utils');
 
 module.exports = defineTest({
diff --git a/test/cli/index.js b/test/cli/index.js
index 02f667cabde..d287bfd3684 100644
--- a/test/cli/index.js
+++ b/test/cli/index.js
@@ -57,8 +57,10 @@ async function runTest(config, command) {
 				env: { ...process.env, FORCE_COLOR: '0', ...config.env },
 				killSignal: 'SIGKILL'
 			},
-			(error, code, stderr) => {
-				if (config.after) config.after(error, code, stderr);
+			async (error, code, stderr) => {
+				if (config.after) {
+					await config.after(error, code, stderr);
+				}
 				if (error && !error.killed) {
 					if (config.error) {
 						if (!config.error(error)) {
@@ -94,7 +96,7 @@ async function runTest(config, command) {
 						}
 
 						if (config.exports) {
-							config.exports(module.exports);
+							await config.exports(module.exports);
 						}
 					} catch (error) {
 						if (config.error) {
diff --git a/test/cli/samples/config-type-module/_config.js b/test/cli/samples/config-type-module/_config.js
index f586b2ac67f..772593d9d2a 100644
--- a/test/cli/samples/config-type-module/_config.js
+++ b/test/cli/samples/config-type-module/_config.js
@@ -1,3 +1,4 @@
+// @ts-expect-error not included in types
 const { assertIncludes } = require('../../../utils.js');
 
 module.exports = defineTest({
diff --git a/test/file-hashes/index.js b/test/file-hashes/index.js
index 74e5ed61446..360b6396cfb 100644
--- a/test/file-hashes/index.js
+++ b/test/file-hashes/index.js
@@ -2,7 +2,9 @@ const path = require('node:path');
 /**
  * @type {import('../../src/rollup/types')} Rollup
  */
+// @ts-expect-error not included in types
 const rollup = require('../../dist/rollup');
+// @ts-expect-error not included in types
 const { runTestSuiteWithSamples } = require('../utils.js');
 
 runTestSuiteWithSamples(
diff --git a/test/form/index.js b/test/form/index.js
index 1761eb74b56..e45c7e1aa90 100644
--- a/test/form/index.js
+++ b/test/form/index.js
@@ -4,78 +4,92 @@ const { basename, resolve } = require('node:path');
 /**
  * @type {import('../../src/rollup/types')} Rollup
  */
+// @ts-expect-error not included in types
 const { rollup } = require('../../dist/rollup');
 const { normaliseOutput, runTestSuiteWithSamples } = require('../utils.js');
 
 const FORMATS = ['amd', 'cjs', 'system', 'es', 'iife', 'umd'];
 
-runTestSuiteWithSamples('form', resolve(__dirname, 'samples'), (directory, config) => {
-	const isSingleFormatTest = existsSync(directory + '/_expected.js');
-	const itOrDescribe = isSingleFormatTest ? it : describe;
-	(config.skip ? itOrDescribe.skip : config.solo ? itOrDescribe.only : itOrDescribe)(
-		basename(directory) + ': ' + config.description,
-		() => {
-			let bundle;
-			const runRollupTest = async (inputFile, bundleFile, defaultFormat) => {
-				const warnings = [];
-				if (config.before) config.before();
-				try {
-					process.chdir(directory);
-					bundle =
-						bundle ||
-						(await rollup({
-							input: directory + '/main.js',
-							onwarn: warning => {
-								if (!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))) {
-									warnings.push(warning);
-								}
+runTestSuiteWithSamples(
+	'form',
+	resolve(__dirname, 'samples'),
+	/**
+	 * @param {import('../types').TestConfigForm} config
+	 */
+	(directory, config) => {
+		const isSingleFormatTest = existsSync(directory + '/_expected.js');
+		const itOrDescribe = isSingleFormatTest ? it : describe;
+		(config.skip ? itOrDescribe.skip : config.solo ? itOrDescribe.only : itOrDescribe)(
+			basename(directory) + ': ' + config.description,
+			() => {
+				let bundle;
+				const runRollupTest = async (inputFile, bundleFile, defaultFormat) => {
+					const warnings = [];
+					if (config.before) {
+						await config.before();
+					}
+					try {
+						process.chdir(directory);
+						bundle =
+							bundle ||
+							(await rollup({
+								input: directory + '/main.js',
+								onwarn: warning => {
+									if (
+										!(config.expectedWarnings && config.expectedWarnings.includes(warning.code))
+									) {
+										warnings.push(warning);
+									}
+								},
+								strictDeprecations: true,
+								...config.options
+							}));
+						await generateAndTestBundle(
+							bundle,
+							{
+								exports: 'auto',
+								file: inputFile,
+								format: defaultFormat,
+								validate: true,
+								...(config.options || {}).output
 							},
-							strictDeprecations: true,
-							...config.options
-						}));
-					await generateAndTestBundle(
-						bundle,
-						{
-							exports: 'auto',
-							file: inputFile,
-							format: defaultFormat,
-							validate: true,
-							...(config.options || {}).output
-						},
-						bundleFile,
-						config
-					);
-				} finally {
-					if (config.after) config.after();
-				}
-				if (warnings.length > 0) {
-					const codes = new Set();
-					for (const { code } of warnings) {
-						codes.add(code);
+							bundleFile,
+							config
+						);
+					} finally {
+						if (config.after) {
+							await config.after();
+						}
 					}
-					throw new Error(
-						`Unexpected warnings (${[...codes].join(', ')}): \n${warnings
-							.map(({ message }) => `${message}\n\n`)
-							.join('')}` + 'If you expect warnings, list their codes in config.expectedWarnings'
-					);
+					if (warnings.length > 0) {
+						const codes = new Set();
+						for (const { code } of warnings) {
+							codes.add(code);
+						}
+						throw new Error(
+							`Unexpected warnings (${[...codes].join(', ')}): \n${warnings
+								.map(({ message }) => `${message}\n\n`)
+								.join('')}` + 'If you expect warnings, list their codes in config.expectedWarnings'
+						);
+					}
+				};
+
+				if (isSingleFormatTest) {
+					return runRollupTest(directory + '/_actual.js', directory + '/_expected.js', 'es');
 				}
-			};
 
-			if (isSingleFormatTest) {
-				return runRollupTest(directory + '/_actual.js', directory + '/_expected.js', 'es');
+				for (const format of config.formats || FORMATS)
+					it('generates ' + format, () =>
+						runRollupTest(
+							directory + '/_actual/' + format + '.js',
+							directory + '/_expected/' + format + '.js',
+							format
+						)
+					);
 			}
-
-			for (const format of config.formats || FORMATS)
-				it('generates ' + format, () =>
-					runRollupTest(
-						directory + '/_actual/' + format + '.js',
-						directory + '/_expected/' + format + '.js',
-						format
-					)
-				);
-		}
-	);
-});
+		);
+	}
+);
 
 async function generateAndTestBundle(bundle, outputOptions, expectedFile, { show }) {
 	await bundle.write(outputOptions);
diff --git a/test/form/samples/addon-functions/_config.js b/test/form/samples/addon-functions/_config.js
index b7c5b899b3b..3379a2debf8 100644
--- a/test/form/samples/addon-functions/_config.js
+++ b/test/form/samples/addon-functions/_config.js
@@ -1,4 +1,5 @@
 const assert = require('node:assert');
+// @ts-expect-error not included in types
 const { replaceDirectoryInStringifiedObject } = require('../../../utils');
 const assertChunkData = chunk =>
 	assert.strictEqual(
diff --git a/test/form/samples/import-assertions/keep-dynamic-assertions/_config.js b/test/form/samples/import-assertions/keep-dynamic-assertions/_config.js
index 0d2f5af3c66..6cd9a15555a 100644
--- a/test/form/samples/import-assertions/keep-dynamic-assertions/_config.js
+++ b/test/form/samples/import-assertions/keep-dynamic-assertions/_config.js
@@ -1,6 +1,6 @@
 module.exports = defineTest({
 	description: 'keep import assertions for dynamic imports',
-	expectedWarnings: 'UNRESOLVED_IMPORT',
+	expectedWarnings: ['UNRESOLVED_IMPORT'],
 	options: {
 		external: id => {
 			if (id === 'unresolved') return null;
diff --git a/test/form/samples/import-assertions/keeps-static-assertions/_config.js b/test/form/samples/import-assertions/keeps-static-assertions/_config.js
index 8780ad60a25..5dfbc1b2c0e 100644
--- a/test/form/samples/import-assertions/keeps-static-assertions/_config.js
+++ b/test/form/samples/import-assertions/keeps-static-assertions/_config.js
@@ -1,6 +1,6 @@
 module.exports = defineTest({
 	description: 'keeps any import assertions on input',
-	expectedWarnings: 'UNRESOLVED_IMPORT',
+	expectedWarnings: ['UNRESOLVED_IMPORT'],
 	options: {
 		external: id => {
 			if (id === 'unresolved') return null;
diff --git a/test/form/samples/import-assertions/removes-dynamic-assertions/_config.js b/test/form/samples/import-assertions/removes-dynamic-assertions/_config.js
index e16ab4730a8..5330ee734d0 100644
--- a/test/form/samples/import-assertions/removes-dynamic-assertions/_config.js
+++ b/test/form/samples/import-assertions/removes-dynamic-assertions/_config.js
@@ -1,6 +1,6 @@
 module.exports = defineTest({
 	description: 'keep import assertions for dynamic imports',
-	expectedWarnings: 'UNRESOLVED_IMPORT',
+	expectedWarnings: ['UNRESOLVED_IMPORT'],
 	options: {
 		external: id => {
 			if (id === 'unresolved') return null;
diff --git a/test/form/samples/import-assertions/removes-static-assertions/_config.js b/test/form/samples/import-assertions/removes-static-assertions/_config.js
index e48102f7749..8f8d7c07fd6 100644
--- a/test/form/samples/import-assertions/removes-static-assertions/_config.js
+++ b/test/form/samples/import-assertions/removes-static-assertions/_config.js
@@ -1,6 +1,6 @@
 module.exports = defineTest({
 	description: 'keeps any import assertions on input',
-	expectedWarnings: 'UNRESOLVED_IMPORT',
+	expectedWarnings: ['UNRESOLVED_IMPORT'],
 	options: {
 		external: id => {
 			if (id === 'unresolved') return null;
diff --git a/test/function/index.js b/test/function/index.js
index 56c8e81269d..80995398251 100644
--- a/test/function/index.js
+++ b/test/function/index.js
@@ -3,6 +3,7 @@ const path = require('node:path');
 /**
  * @type {import('../../src/rollup/types')} Rollup
  */
+// @ts-expect-error not included in types
 const rollup = require('../../dist/rollup');
 const { compareError, compareWarnings, runTestSuiteWithSamples } = require('../utils.js');
 
@@ -58,9 +59,11 @@ runTestSuiteWithSamples(
 	(directory, config) => {
 		(config.skip ? it.skip : config.solo ? it.only : it)(
 			path.basename(directory) + ': ' + config.description,
-			() => {
+			async () => {
 				if (config.show) console.group(path.basename(directory));
-				if (config.before) config.before();
+				if (config.before) {
+					await config.before();
+				}
 				process.chdir(directory);
 				const warnings = [];
 
@@ -173,7 +176,9 @@ runTestSuiteWithSamples(
 										}
 										if (config.show) console.groupEnd();
 										if (unintendedError) throw unintendedError;
-										if (config.after) config.after();
+										if (config.after) {
+											return config.after();
+										}
 									});
 							});
 					})
@@ -183,7 +188,9 @@ runTestSuiteWithSamples(
 						} else {
 							throw error;
 						}
-						if (config.after) config.after();
+						if (config.after) {
+							return config.after();
+						}
 					});
 			}
 		);
diff --git a/test/sourcemaps/samples/transform-without-sourcemap-render-chunk/_config.js b/test/function/samples/transform-without-sourcemap-render-chunk/_config.js
similarity index 95%
rename from test/sourcemaps/samples/transform-without-sourcemap-render-chunk/_config.js
rename to test/function/samples/transform-without-sourcemap-render-chunk/_config.js
index 11336d4d5cf..46076d52430 100644
--- a/test/sourcemaps/samples/transform-without-sourcemap-render-chunk/_config.js
+++ b/test/function/samples/transform-without-sourcemap-render-chunk/_config.js
@@ -17,7 +17,8 @@ module.exports = defineTest({
 					return { code, map: null };
 				}
 			}
-		]
+		],
+		output: { sourcemap: true }
 	},
 	warnings: [
 		{
diff --git a/test/function/samples/transform-without-sourcemap-render-chunk/main.js b/test/function/samples/transform-without-sourcemap-render-chunk/main.js
new file mode 100644
index 00000000000..69305ae375a
--- /dev/null
+++ b/test/function/samples/transform-without-sourcemap-render-chunk/main.js
@@ -0,0 +1 @@
+assert.strictEqual(42, 42);
diff --git a/test/sourcemaps/index.js b/test/sourcemaps/index.js
index ece3af688f2..8e49fea4797 100644
--- a/test/sourcemaps/index.js
+++ b/test/sourcemaps/index.js
@@ -2,7 +2,9 @@ const path = require('node:path');
 /**
  * @type {import('../../src/rollup/types')} Rollup
  */
+// @ts-expect-error not included in types
 const rollup = require('../../dist/rollup');
+// @ts-expect-error not included in types
 const { compareWarnings, runTestSuiteWithSamples } = require('../utils.js');
 
 const FORMATS = ['amd', 'cjs', 'system', 'es', 'iife', 'umd'];
@@ -10,11 +12,14 @@ const FORMATS = ['amd', 'cjs', 'system', 'es', 'iife', 'umd'];
 runTestSuiteWithSamples(
 	'sourcemaps',
 	path.resolve(__dirname, 'samples'),
-	(directory, configuration) => {
-		(configuration.skip ? describe.skip : configuration.solo ? describe.only : describe)(
-			path.basename(directory) + ': ' + configuration.description,
+	/**
+	 * @param {import('../types').TestConfigSourcemap} config
+	 */
+	(directory, config) => {
+		(config.skip ? describe.skip : config.solo ? describe.only : describe)(
+			path.basename(directory) + ': ' + config.description,
 			() => {
-				for (const format of configuration.formats || FORMATS) {
+				for (const format of config.formats || FORMATS) {
 					it('generates ' + format, async () => {
 						process.chdir(directory);
 						const warnings = [];
@@ -22,25 +27,25 @@ runTestSuiteWithSamples(
 							input: directory + '/main.js',
 							onwarn: warning => warnings.push(warning),
 							strictDeprecations: true,
-							...configuration.options
+							...config.options
 						};
 						const outputOptions = {
 							exports: 'auto',
 							file: directory + '/_actual/bundle.' + format + '.js',
 							format,
 							sourcemap: true,
-							...(configuration.options || {}).output
+							...(config.options || {}).output
 						};
 
 						let bundle = await rollup.rollup(inputOptions);
-						await generateAndTestBundle(bundle, outputOptions, configuration, format, warnings);
+						await generateAndTestBundle(bundle, outputOptions, config, format, warnings);
 						// cache rebuild does not reemit warnings.
-						if (configuration.warnings) {
+						if (config.warnings) {
 							return;
 						}
 						// test cache noop rebuild
 						bundle = await rollup.rollup({ cache: bundle, ...inputOptions });
-						await generateAndTestBundle(bundle, outputOptions, configuration, format, warnings);
+						await generateAndTestBundle(bundle, outputOptions, config, format, warnings);
 					});
 				}
 			}
@@ -48,17 +53,14 @@ runTestSuiteWithSamples(
 	}
 );
 
-async function generateAndTestBundle(bundle, outputOptions, configuration, format, warnings) {
-	await bundle.write(outputOptions);
-	if (configuration.warnings) {
-		compareWarnings(warnings, configuration.warnings);
+async function generateAndTestBundle(bundle, outputOptions, config, format, warnings) {
+	if (config.warnings) {
+		compareWarnings(warnings, config.warnings);
 	} else if (warnings.length > 0) {
 		throw new Error(`Unexpected warnings`);
 	}
-	if (configuration.test) {
-		const {
-			output: [{ code, map, fileName }]
-		} = await bundle.generate(outputOptions);
-		await configuration.test(code, map, { fileName, format });
-	}
+	const {
+		output: [{ code, map, fileName }]
+	} = await bundle.generate(outputOptions);
+	await config.test(code, map, { fileName, format });
 }
diff --git a/test/sourcemaps/samples/transform-without-sourcemap-render-chunk/main.js b/test/sourcemaps/samples/transform-without-sourcemap-render-chunk/main.js
deleted file mode 100644
index 5c72ff35124..00000000000
--- a/test/sourcemaps/samples/transform-without-sourcemap-render-chunk/main.js
+++ /dev/null
@@ -1 +0,0 @@
-console.log( 42 );
diff --git a/test/types.d.ts b/test/types.d.ts
index 1a8a28cbdb6..d9d31b6f4dd 100644
--- a/test/types.d.ts
+++ b/test/types.d.ts
@@ -1,127 +1,233 @@
-/* eslint-disable @typescript-eslint/member-ordering */
 import type { SourceMap } from 'magic-string';
 import type { RollupBuild, RollupError, RollupOptions } from '../src/rollup/types';
 
 export interface TestConfigBase {
 	/**
-	 * Only run this test. Should never be committed.
+	 * Description of the test. Determines the name of the test in the test
+	 * runner.
 	 */
-	solo?: boolean;
+	description: string;
+	/**
+	 * Only run this test if the major Node version is high enough.
+	 */
+	minNodeVersion?: number;
+	/**
+	 * Only run this test on Windows.
+	 */
+	onlyWindows?: boolean;
 	/**
 	 * Skip this test.
 	 */
 	skip?: boolean;
 	/**
-	 * Display in the test output.
+	 * Do not run this test on Windows.
 	 */
-	show?: boolean;
+	skipIfWindows?: boolean;
 	/**
-	 * Execute the bundled code.
+	 * Only run this test. Should never be committed.
 	 */
-	execute?: boolean;
+	solo?: boolean;
+}
 
+export interface TestConfigBrowser extends TestConfigBase {
 	/**
-	 * Description of the test.
+	 * Expected error when running rollup.rollup()
 	 */
-	description: string;
+	error?: RollupError;
 	/**
-	 * Rollup options
+	 * Expected warning codes. Any of these warnings will not cause the test to
+	 * fail.
+	 */
+	expectedWarnings?: string[];
+	/**
+	 * Expected error when running bundle.generate().
+	 */
+	generateError?: RollupError;
+	/**
+	 * Rollup options for bundling.
 	 */
 	options?: RollupOptions;
+}
+
+export interface TestConfigChunkingForm extends TestConfigBase {
 	/**
-	 * Bundle formats to test.
+	 * Called after the test is run.
 	 */
-	formats?: string[];
+	after?: () => void | Promise<void>;
 	/**
-	 * The global context executed the bundled code.
+	 * Called before the test is run.
 	 */
-	context?: Record<string, any>;
+	before?: () => void | Promise<void>;
 	/**
-	 * The directory to run the test in.
+	 * Expected warning codes. Any of these warnings will not cause the test to
+	 * fail.
+	 */
+	expectedWarnings?: string[];
+	/**
+	 * The directory to bundle the code in.
 	 */
 	nestedDir?: string;
+	/**
+	 * Rollup options for bundling.
+	 */
+	options?: RollupOptions;
+	/**
+	 * Execute the AMD module.
+	 */
+	runAmd?:
+		| boolean
+		| {
+				exports?: (exportObject: any) => void | Promise<void>;
+		  };
+}
 
+export interface TestConfigCli extends TestConfigBase {
 	/**
-	 * Called before the test is run.
+	 * Assert the stderr stream, return true to abort the test.
 	 */
-	before?: () => void | Promise<void>;
+	abortOnStderr?: (data: string) => boolean | void | Promise<boolean | void>;
 	/**
 	 * Called after the test is run.
 	 */
-	after?: () => void | Promise<void>;
-
+	after?: (error: Error | null, stdout: string, stderr: string) => void | Promise<void>;
 	/**
-	 * Test the expected error.
+	 * Called before the test is run.
 	 */
-	error?: RollupError;
-	generateError?: RollupError;
+	before?: () => void | Promise<void>;
+	command?: string;
+	cwd?: string;
 	/**
-	 * Test the expected warnings.
+	 * Environment variables to set for the test.
 	 */
-	warnings?: RollupError[] | ((warnings: RollupError[]) => boolean | void);
+	env?: Record<string, string | boolean | undefined>;
 	/**
-	 * Expected warning codes
+	 * Test the expected error. Assertions about the test output will only
+	 * be performed afterward if you return "true" or do not supply this option.
 	 */
-	expectedWarnings?: string | string[];
+	error?: (error: RollupError) => boolean | void;
 	/**
-	 * Test the output of the build.
+	 * Execute the bundled code.
 	 */
-	test?: (code: string, map: SourceMap) => void | Promise<void>;
+	execute?: boolean;
 	/**
-	 * Assetions for the exports of the bundle.
+	 * Run assertions against the exports of the bundle after executing it.
 	 */
 	exports?: (exportObject: any) => void | Promise<void>;
-
-	skipIfWindows?: boolean;
-	onlyWindows?: boolean;
-	minNodeVersion?: string;
+	/**
+	 * Run assertions against the generated code when bundling to stdout.
+	 */
+	result?: (code: string) => void;
+	retry?: number;
+	/**
+	 * Display generated output in console.
+	 */
+	show?: boolean;
+	/**
+	 * Assert the stderr of the build. Assertions about the test output will only
+	 * be performed afterward if you return "true" or do not supply this option.
+	 */
+	stderr?: (stderr: string) => boolean | undefined;
+	/**
+	 * Run assertions after the command has finished.
+	 */
+	test?: () => void;
 }
 
-// eslint-disable-next-line @typescript-eslint/no-empty-interface
-export interface TestConfigForm extends TestConfigBase {}
-// eslint-disable-next-line @typescript-eslint/no-empty-interface
-export interface TestConfigSourcemap extends TestConfigBase {}
-
 export interface TestConfigFileHash extends TestConfigBase {
-	options1?: RollupOptions;
-	options2?: RollupOptions;
+	options1: RollupOptions;
+	options2: RollupOptions;
 }
 
-export interface TestConfigCli extends TestConfigBase {
-	command?: string;
-	cwd?: string;
-	retry?: number;
+export interface TestConfigForm extends TestConfigBase {
 	/**
-	 * Environment variables to set for the test.
+	 * Called after the test is run.
 	 */
-	env?: Record<string, string | boolean | undefined>;
+	after?: () => void | Promise<void>;
 	/**
-	 * Assert the stderr of the build.
+	 * Called before the test is run.
 	 */
-	stderr?: (stderr: string) => void | Promise<void>;
+	before?: () => void | Promise<void>;
 	/**
-	 * Assert the stderr stream, return true to abort the test.
+	 * Expected warning codes. Any of these warnings will not cause the test to
+	 * fail.
 	 */
-	abortOnStderr?: (data: string) => boolean | void | Promise<boolean | void>;
-
-	result?: (code: string) => void;
-}
-
-export interface TestConfigChunkingForm extends TestConfigBase {
+	expectedWarnings?: string[];
 	/**
-	 * Execute the AMD module.
+	 * Output formats to test.
 	 */
-	runAmd?:
-		| boolean
-		| {
-				exports?: (exportObject: any) => void | Promise<void>;
-		  };
+	formats?: string[];
+	/**
+	 * Rollup options for bundling.
+	 */
+	options?: RollupOptions;
 }
 
 export interface TestConfigFunction extends TestConfigBase {
-	runtimeError?(error: Error): void;
-	bundle?(bundle: RollupBuild): void;
-	code?(code: string): void;
+	/**
+	 * Called after the test is run.
+	 */
+	after?: () => void | Promise<void>;
+	/**
+	 * Called before the test is run.
+	 */
+	before?: () => void | Promise<void>;
+	/**
+	 * Make assertions against the generated Rollup output object.
+	 */
+	bundle?: (bundle: RollupBuild) => void | Promise<void>;
+	/**
+	 * Make assertions against the generated code.
+	 */
+	code?: (code: string | Record<string, string>) => void;
+	/**
+	 * The global context executed the bundled code.
+	 */
+	context?: Record<string, any>;
+	/**
+	 * Expected error when running rollup.rollup()
+	 */
+	error?: RollupError;
+	/**
+	 * Assetions for the exports of the bundle.
+	 */
+	exports?: (exportObject: any) => void | Promise<void>;
+	/**
+	 * Expected error when running bundle.generate().
+	 */
+	generateError?: RollupError;
+	/**
+	 * Make assertions against an expected runtime error.
+	 */
+	runtimeError?: (error: Error) => void;
+	/**
+	 * Display generated output in console.
+	 */
+	show?: boolean;
+	/**
+	 * Test the expected warnings.
+	 */
+	warnings?: RollupError[] | ((warnings: RollupError[]) => boolean | void);
 }
 
-export type RunTestFunction = <C extends TestConfigBase>(directory: string, config: C) => void;
+export interface TestConfigSourcemap extends TestConfigBase {
+	/**
+	 * Output formats to test.
+	 */
+	formats?: string[];
+	/**
+	 * Rollup options for bundling.
+	 */
+	options?: RollupOptions;
+	/**
+	 * Generate the bundle and run assertions.
+	 */
+	test: (
+		code: string,
+		map: SourceMap,
+		options: { fileName: string; format: string }
+	) => void | Promise<void>;
+	/**
+	 * List expected warnings.
+	 */
+	warnings?: RollupError[];
+}