diff --git a/test/dist.test.js b/test/dist.test.js
index 23a5564..c7a021b 100644
--- a/test/dist.test.js
+++ b/test/dist.test.js
@@ -1,5 +1,4 @@
 /* eslint-env es6, node */
-'use strict';
 
 /* note: dynamic imports are used because 'dist' may not exist */
 
diff --git a/test/integration.test.js b/test/integration.test.js
index 1c227c9..a0b5e32 100644
--- a/test/integration.test.js
+++ b/test/integration.test.js
@@ -4,8 +4,6 @@
 
 // spell-checker:ignore (names) Deno ; (vars) ESM ESMs vNodeJSMajor vNodeJSminor ; (words) cyclomatic
 
-'use strict';
-
 const fs = require('fs');
 const path = require('path');
 const util = require('util');
diff --git a/test/unit.test.js b/test/unit.test.js
index 8c24967..149cdbd 100644
--- a/test/unit.test.js
+++ b/test/unit.test.js
@@ -1,7 +1,6 @@
 /* eslint-disable functional/immutable-data , functional/no-loop-statement , security-node/non-literal-reg-expr , security/detect-non-literal-regexp , security/detect-object-injection */
 /* eslint-env es6, node */
 // spell-checker:ignore (vars) ESM ESMs vNodeJSMajor vNodeJSminor
-'use strict';
 
 const path = require('path');
 
@@ -26,13 +25,14 @@ function typeOf(value) {
 
 function xdgPathRegex(name) {
 	return new RegExp(
+		// biome-ignore lint/style/useTemplate: # better clarity with comment
 		'(^|' +
 			regexpEscape(path.sep) +
 			')' +
 			regexpEscape(name) +
 			'(' +
 			// for windows, `name` may be embedded within the generated paths (instead of always trailing as in MacOS/*nix)
-			(isWinOS ? regexpEscape(path.sep) + '|' : '') +
+			(isWinOS ? `${regexpEscape(path.sep)}|` : '') +
 			'$)',
 	);
 }
@@ -324,8 +324,8 @@ test('correct paths with only XDG_*_HOME set', (t) => {
 		data: 'XDG_DATA_HOME',
 		state: 'XDG_STATE_HOME',
 	};
-	delete process.env.XDG_CONFIG_DIRS;
-	delete process.env.XDG_DATA_DIRS;
+	process.env.XDG_CONFIG_DIRS = void 0;
+	process.env.XDG_DATA_DIRS = void 0;
 	Object.keys(envVars).forEach((key) => {
 		const env = envVars[key];
 		process.env[env] = path.join('.', env);
@@ -385,8 +385,8 @@ test('correct "isolated" paths with only XDG_*_HOME set', (t) => {
 		data: 'XDG_DATA_HOME',
 		state: 'XDG_STATE_HOME',
 	};
-	delete process.env.XDG_CONFIG_DIRS;
-	delete process.env.XDG_DATA_DIRS;
+	process.env.XDG_CONFIG_DIRS = void 0;
+	process.env.XDG_DATA_DIRS = void 0;
 	for (const key of Object.keys(envVars)) {
 		const env = envVars[key];
 		process.env[env] = path.join('.', env);
@@ -446,8 +446,8 @@ test('correct non-"isolated" paths with only XDG_*_HOME set', (t) => {
 		data: 'XDG_DATA_HOME',
 		state: 'XDG_STATE_HOME',
 	};
-	delete process.env.XDG_CONFIG_DIRS;
-	delete process.env.XDG_DATA_DIRS;
+	process.env.XDG_CONFIG_DIRS = void 0;
+	process.env.XDG_DATA_DIRS = void 0;
 	Object.keys(envVars).forEach((key) => {
 		const env = envVars[key];
 		process.env[env] = path.join('.', env);
@@ -685,8 +685,7 @@ test('correct non-"isolated" paths with XDG_* set', (t) => {
 test('correctly derive anonymous (CJS)', (t) => {
 	const command = 'node';
 	process.env.TEST_MODULE_PATH = './build/lab/src/mod.cjs.js';
-	const script =
-		'"p = require(\'' + process.env.TEST_MODULE_PATH + '\'); console.log(p.$name({}));"';
+	const script = `"p = require('${process.env.TEST_MODULE_PATH}'); console.log(p.$name({}));"`;
 	const args = ['-e', isWinOS ? script : script.replace('$name', '\\$name')];
 	const options = { shell: true, encoding: 'utf-8' };
 
@@ -705,8 +704,7 @@ if (settledSupportForESMs) {
 	test('correctly derive anonymous (ESM/[import CJS])', (t) => {
 		const command = 'node';
 		process.env.TEST_MODULE_PATH = './build/lab/src/mod.cjs.js';
-		const script =
-			'"import p from \'' + process.env.TEST_MODULE_PATH + '\'; console.log(p.$name({}));"';
+		const script = `"import p from '${process.env.TEST_MODULE_PATH}'; console.log(p.$name({}));"`;
 		const args = [
 			'--input-type=module',
 			'-e',
@@ -728,8 +726,7 @@ if (settledSupportForESMs) {
 	test('correctly derive anonymous (ESM/[esm-wrapper])', (t) => {
 		const command = 'node';
 		process.env.TEST_MODULE_PATH = './build/lab/src/esm-wrapper/mod.esm.js';
-		const script =
-			'"import p from \'' + process.env.TEST_MODULE_PATH + '\'; console.log(p.$name({}));"';
+		const script = `"import p from '${process.env.TEST_MODULE_PATH}'; console.log(p.$name({}));"`;
 		const args = [
 			'--input-type=module',
 			'-e',
@@ -751,8 +748,7 @@ if (settledSupportForESMs) {
 	test('correctly derive anonymous (ESM)', (t) => {
 		const command = 'node';
 		process.env.TEST_MODULE_PATH = './build/esm/src/mod.esm.js';
-		const script =
-			'"import p from \'' + process.env.TEST_MODULE_PATH + '\'; console.log(p.$name({}));"';
+		const script = `"import p from '${process.env.TEST_MODULE_PATH}'; console.log(p.$name({}));"`;
 		const args = [
 			'--input-type=module',
 			'-e',