diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..986df3b
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,12 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = tab
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[{README.md,*.yml,*.d.ts}]
+indent_style = space
+indent_size = 2
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
new file mode 100644
index 0000000..29966a2
--- /dev/null
+++ b/.github/workflows/main.yml
@@ -0,0 +1,31 @@
+name: run-checks
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        # Include all major maintenance + active LTS + current Node.js versions.
+        # https://github.com/nodejs/Release#release-schedule
+        node: [12, 14, 16]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Set up Node.js
+        uses: actions/setup-node@v1
+        with:
+          node-version: ${{ matrix.node }}
+      - name: Install dependencies
+        run: npm install
+      - name: Build
+        run: npm run build
+      - name: Test
+        run: npm test
diff --git a/.github/workflows/publish-on-tag.yml b/.github/workflows/publish-on-tag.yml
index 10d7ad5..b0e5835 100644
--- a/.github/workflows/publish-on-tag.yml
+++ b/.github/workflows/publish-on-tag.yml
@@ -3,7 +3,7 @@ name: publish-on-tag
 on:
   push:
     tags:
-    - '*'
+      - '*'
 
 jobs:
   publish:
@@ -11,6 +11,12 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+      - name: Install dependencies
+        run: npm install
+      - name: Build
+        run: npm run build
+      - name: Test
+        run: npm test
       - name: Publish
         env:
           NPM_TOKEN: ${{secrets.NPM_TOKEN}}
diff --git a/Gruntfile.js b/Gruntfile.js
deleted file mode 100644
index 74cf2ee..0000000
--- a/Gruntfile.js
+++ /dev/null
@@ -1,93 +0,0 @@
-module.exports = function(grunt) {
-
-	grunt.initConfig({
-		'shell': {
-			'options': {
-				'stdout': true,
-				'stderr': true,
-				'failOnError': true
-			},
-			'transform-data': {
-				'command': 'npm run build'
-			},
-			'cover-html': {
-				'command': 'istanbul cover --report "html" --verbose --dir "coverage" "tests/tests.js"'
-			},
-			'cover-coveralls': {
-				'command': 'istanbul cover --verbose --dir "coverage" "tests/tests.js" && coveralls < coverage/lcov.info; rm -rf coverage/lcov*'
-			},
-			'test-narwhal': {
-				'command': 'echo "Testing in Narwhal..."; export NARWHAL_OPTIMIZATION=-1; narwhal "tests/tests.js"'
-			},
-			'test-phantomjs': {
-				'command': 'echo "Testing in PhantomJS..."; phantomjs "tests/tests.js"'
-			},
-			'test-rhino': {
-				'command': 'echo "Testing in Rhino..."; rhino -opt -1 "tests.js"',
-				'options': {
-					'execOptions': {
-						'cwd': 'tests'
-					}
-				}
-			},
-			'test-ringo': {
-				'command': 'echo "Testing in Ringo..."; ringo -o -1 "tests/tests.js"'
-			},
-			'test-node': {
-				'command': 'echo "Testing in Node..."; node "tests/tests.js"'
-			},
-			'test-browser': {
-				'command': 'echo "Testing in a browser..."; open "tests/index.html"'
-			}
-		},
-		'template': {
-			'build': {
-				'options': {
-					'data': function() {
-						return require('./scripts/export-data.js');
-					}
-				},
-				'files': {
-					'koi8-r.js': ['src/koi8-r.js']
-				}
-			},
-			'build-tests': {
-				'options': {
-					'data': function() {
-						return require('./scripts/export-data.js');
-					}
-				},
-				'files': {
-					'tests/tests.js': ['tests/tests.src.js']
-				}
-			}
-		}
-	});
-
-	grunt.loadNpmTasks('grunt-shell');
-	grunt.loadNpmTasks('grunt-template');
-
-	grunt.registerTask('cover', 'shell:cover-html');
-	grunt.registerTask('ci', [
-		'shell:test-narwhal',
-		'shell:test-phantomjs',
-		'shell:test-rhino',
-		'shell:test-ringo',
-		'shell:test-node'
-	]);
-	grunt.registerTask('test', [
-		'ci',
-		'shell:test-browser'
-	]);
-
-	grunt.registerTask('build', [
-		'shell:transform-data',
-		'default'
-	]);
-
-	grunt.registerTask('default', [
-		'template',
-		'shell:test-node'
-	]);
-
-};
diff --git a/README.md b/README.md
index 9224a7c..39f95b9 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# koi8-r [![koi8-r on npm](https://img.shields.io/npm/v/koi8-r)](https://www.npmjs.com/package/koi8-r)
+# koi8-r [![Build status](https://github.com/mathiasbynens/koi8-r/workflows/run-checks/badge.svg)](https://github.com/mathiasbynens/koi8-r/actions?query=workflow%3Arun-checks) [![koi8-r on npm](https://img.shields.io/npm/v/koi8-r)](https://www.npmjs.com/package/koi8-r)
 
 _koi8-r_ is a robust JavaScript implementation of [the koi8-r character encoding as defined by the Encoding Standard](https://encoding.spec.whatwg.org/#koi8-r).
 
diff --git a/data/index.txt b/data/index.txt
index f8d6dff..639e9c4 100644
--- a/data/index.txt
+++ b/data/index.txt
@@ -1,11 +1,8 @@
-# Any copyright is dedicated to the Public Domain.
-# https://creativecommons.org/publicdomain/zero/1.0/
-#
 # For details on index index-koi8-r.txt see the Encoding Standard
 # https://encoding.spec.whatwg.org/
 #
 # Identifier: c5497cd9071cb352c0e56b219154e539badf63de40b71578f09e2e11fe7d50ae
-# Date: 2016-01-20
+# Date: 2018-01-06
 
   0	0x2500	─ (BOX DRAWINGS LIGHT HORIZONTAL)
   1	0x2502	│ (BOX DRAWINGS LIGHT VERTICAL)
diff --git a/package.json b/package.json
index 348be12..ad4c72e 100644
--- a/package.json
+++ b/package.json
@@ -35,18 +35,12 @@
 	"scripts": {
 		"download": "curl https://encoding.spec.whatwg.org/index-koi8-r.txt > data/index.txt",
 		"build": "node scripts/transform-data.js",
-		"test": "node tests/tests.js"
+		"test": "node tests/tests.js",
+		"cover": "istanbul cover --report html --verbose --dir coverage tests/tests.js"
 	},
 	"devDependencies": {
-		"coveralls": "^2.11.6",
-		"grunt": "^0.4.5",
-		"grunt-shell": "^1.1.2",
-		"grunt-template": "^0.2.3",
 		"istanbul": "^0.4.2",
-		"jsesc": "^2.1.0",
-		"qunit-extras": "^1.4.5",
-		"qunitjs": "~1.11.0",
-		"requirejs": "^2.1.22",
-		"string.fromcodepoint": "^0.2.1"
+		"jsesc": "^3.0.2",
+		"lodash.template": "^4.5.0"
 	}
 }
diff --git a/scripts/export-data.js b/scripts/export-data.js
index 8b9e2c9..8fa0665 100644
--- a/scripts/export-data.js
+++ b/scripts/export-data.js
@@ -1,18 +1,18 @@
-var fs = require('fs');
-var jsesc = require('jsesc');
+const fs = require('fs');
+const jsesc = require('jsesc');
 
 function readJSON(path) {
 	return JSON.parse(fs.readFileSync(path, 'utf-8'));
 }
 
 module.exports = {
-	'labels': jsesc(readJSON('data/labels.json'), {
-		'compact': false,
-		'indentLevel': 2
+	labels: jsesc(readJSON('data/labels.json'), {
+		compact: false,
+		indentLevel: 2,
 	}),
-	'encoded': jsesc(readJSON('data/encoded.json'), { 'wrap': true }),
-	'decoded': jsesc(readJSON('data/decoded.json'), { 'wrap': true }),
-	'indexByCodePoint': jsesc(readJSON('data/index-by-code-point.json')),
-	'indexByPointer': jsesc(readJSON('data/index-by-pointer.json')),
-	'version': readJSON('package.json').version
+	encoded: jsesc(readJSON('data/encoded.json'), { wrap: true }),
+	decoded: jsesc(readJSON('data/decoded.json'), { wrap: true }),
+	indexByCodePoint: jsesc(readJSON('data/index-by-code-point.json')),
+	indexByPointer: jsesc(readJSON('data/index-by-pointer.json')),
+	version: readJSON('package.json').version
 };
diff --git a/scripts/transform-data.js b/scripts/transform-data.js
index 9871c23..3d27d51 100644
--- a/scripts/transform-data.js
+++ b/scripts/transform-data.js
@@ -1,43 +1,43 @@
-var fs = require('fs');
-var jsesc = require('jsesc');
-require('string.fromcodepoint');
+const fs = require('fs');
+const jsesc = require('jsesc');
+const template = require('lodash.template');
 
 function format(object) {
 	return jsesc(object, {
-		'json': true,
-		'compact': false
+		json: true,
+		compact: false,
 	}) + '\n';
 }
 
 function parse(source) {
-	var indexByCodePoint = {};
-	var indexByPointer = {};
-	var decoded = '';
-	var encoded = '';
+	const indexByCodePoint = {};
+	const indexByPointer = {};
+	let decoded = '';
+	let encoded = '';
 	var lines = source.split('\n');
-	lines.forEach(function(line) {
-		var data = line.trim().split('\t');
+	for (const line of lines) {
+		const data = line.trim().split('\t');
 		if (data.length != 3) {
-			return;
+			continue;
 		}
-		var pointer = Number(data[0]);
-		var codePoint = Number(data[1]);
-		var symbol = String.fromCodePoint(codePoint);
+		const pointer = Number(data[0]);
+		const codePoint = Number(data[1]);
+		const symbol = String.fromCodePoint(codePoint);
 		decoded += symbol;
 		encoded += String.fromCodePoint(pointer + 0x80);
 		indexByCodePoint[codePoint] = pointer;
 		indexByPointer[pointer] = symbol;
-	});
+	}
 	return {
-		'decoded': decoded,
-		'encoded': encoded,
-		'indexByCodePoint': indexByCodePoint,
-		'indexByPointer': indexByPointer
+		decoded: decoded,
+		encoded: encoded,
+		indexByCodePoint: indexByCodePoint,
+		indexByPointer: indexByPointer
 	};
 }
 
-var source = fs.readFileSync('./data/index.txt', 'utf-8');
-var result = parse(source);
+const source = fs.readFileSync('./data/index.txt', 'utf-8');
+const result = parse(source);
 fs.writeFileSync(
 	'./data/index-by-code-point.json',
 	format(result.indexByCodePoint)
@@ -54,3 +54,19 @@ fs.writeFileSync(
 	'./data/encoded.json',
 	format(result.encoded)
 );
+
+// tests/tests.src.js → tests/tests.js
+const TEST_TEMPLATE = fs.readFileSync('./tests/tests.src.js', 'utf8');
+const createTest = template(TEST_TEMPLATE, {
+	interpolate: /<\%=([\s\S]+?)%\>/g,
+});
+const testCode = createTest(require('./export-data.js'));
+fs.writeFileSync('./tests/tests.js', testCode);
+
+// src/koi8-r.src.js -> koi8-r.js
+const LIB_TEMPLATE = fs.readFileSync('./src/koi8-r.src.js', 'utf8');
+const createLib = template(LIB_TEMPLATE, {
+	interpolate: /<\%=([\s\S]+?)%\>/g,
+});
+const libCode = createLib(require('./export-data.js'));
+fs.writeFileSync('./koi8-r.js', libCode);
diff --git a/src/koi8-r.js b/src/koi8-r.src.js
similarity index 69%
rename from src/koi8-r.js
rename to src/koi8-r.src.js
index 989b6ee..c7d7f2d 100644
--- a/src/koi8-r.js
+++ b/src/koi8-r.src.js
@@ -1,21 +1,5 @@
 /*! https://mths.be/koi8-r v<%= version %> by @mathias | MIT license */
-;(function(root) {
-
-	// Detect free variables `exports`.
-	var freeExports = typeof exports == 'object' && exports;
-
-	// Detect free variable `module`.
-	var freeModule = typeof module == 'object' && module &&
-		module.exports == freeExports && module;
-
-	// Detect free variable `global`, from Node.js/io.js or Browserified code,
-	// and use it as `root`.
-	var freeGlobal = typeof global == 'object' && global;
-	if (freeGlobal.global === freeGlobal || freeGlobal.window === freeGlobal) {
-		root = freeGlobal;
-	}
-
-	/*--------------------------------------------------------------------------*/
+;(function() {
 
 	var object = {};
 	var hasOwnProperty = object.hasOwnProperty;
@@ -33,7 +17,7 @@
 			return '&#' + codePoint + ';';
 		}
 		// Else, `mode == 'fatal'`.
-		throw Error();
+		throw new Error();
 	};
 
 	// https://encoding.spec.whatwg.org/#single-byte-decoder
@@ -113,32 +97,12 @@
 	};
 
 	var koi8r = {
-		'encode': encode,
-		'decode': decode,
-		'labels': <%= labels %>,
-		'version': '<%= version %>'
+		encode: encode,
+		decode: decode,
+		labels: <%= labels %>,
+		version: '<%= version %>',
 	};
 
-	// Some AMD build optimizers, like r.js, check for specific condition patterns
-	// like the following:
-	if (
-		typeof define == 'function' &&
-		typeof define.amd == 'object' &&
-		define.amd
-	) {
-		define(function() {
-			return koi8r;
-		});
-	}	else if (freeExports && !freeExports.nodeType) {
-		if (freeModule) { // in Node.js, io.js or RingoJS v0.8.0+
-			freeModule.exports = koi8r;
-		} else { // in Narwhal or RingoJS v0.7.0-
-			for (var key in koi8r) {
-				koi8r.hasOwnProperty(key) && (freeExports[key] = koi8r[key]);
-			}
-		}
-	} else { // in Rhino or a web browser
-		root.koi8r = koi8r;
-	}
+	module.exports = koi8r;
 
-}(this));
+}());
diff --git a/tests/tests.src.js b/tests/tests.src.js
index 09e688e..dd9ffdc 100644
--- a/tests/tests.src.js
+++ b/tests/tests.src.js
@@ -1,158 +1,111 @@
-(function(root) {
-	'use strict';
+const assert = require('assert');
 
-	var noop = Function.prototype;
+const koi8r = require('../koi8-r.js');
 
-	var load = (typeof require == 'function' && !(root.define && define.amd)) ?
-		require :
-		(!root.document && root.java && root.load) || noop;
+console.log('Testing `koi8r.encode`…');
+assert.strictEqual(
+	koi8r.encode('\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F'),
+	'\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F',
+	'U+0000 to U+007F remain unchanged'
+);
+assert.strictEqual(
+	koi8r.encode(<%= decoded %>),
+	<%= encoded %>,
+	'Encoding all other symbols in the character set'
+);
+assert.throws(
+	() => {
+		koi8r.encode('\uFFFF');
+	},
+	Error,
+	'Encoding a code point that is invalid for this encoding throws an error in `fatal` mode, which is the implied default for `encode()`'
+);
+assert.throws(
+	() => {
+		koi8r.encode('\uFFFF', { mode: 'fatal' });
+	},
+	Error,
+	'Encoding a code point that is invalid for this encoding throws an error in `fatal` mode'
+);
+assert.throws(
+	() => {
+		koi8r.encode('\uFFFF', { mode: 'FATAL' });
+	},
+	Error,
+	'Mode names are case-insensitive'
+);
+assert.throws(
+	() => {
+		koi8r.encode('\uFFFF', { mode: 'fAtAl' });
+	},
+	Error,
+	'Mode names are case-insensitive'
+);
+assert.strictEqual(
+	koi8r.encode('\uFFFF', { mode: 'html' }),
+	'&#65535;',
+	'Encoding a code point that is invalid for this encoding returns an HTML entity in `html` mode'
+);
+assert.strictEqual(
+	koi8r.encode('\uFFFF', { mode: 'HTML' }),
+	'&#65535;',
+	'Mode names are case-insensitive'
+);
+assert.strictEqual(
+	koi8r.encode('\uFFFF', { mode: 'hTmL' }),
+	'&#65535;',
+	'Mode names are case-insensitive'
+);
 
-	var QUnit = (function() {
-		return root.QUnit || (
-			root.addEventListener || (root.addEventListener = noop),
-			root.setTimeout || (root.setTimeout = noop),
-			root.QUnit = load('../node_modules/qunitjs/qunit/qunit.js') || root.QUnit,
-			addEventListener === noop && delete root.addEventListener,
-			root.QUnit
-		);
-	}());
-
-	var qe = load('../node_modules/qunit-extras/qunit-extras.js');
-	if (qe) {
-		qe.runInContext(root);
-	}
-
-	// The `koi8r` object to test
-	var koi8r = root.koi8r || (root.koi8r = (
-		koi8r = load('../koi8-r.js') || root.koi8r,
-		koi8r = koi8r.koi8r || koi8r
-	));
-
-	/*--------------------------------------------------------------------------*/
-
-	// `throws` is a reserved word in ES3; alias it to avoid errors
-	var raises = QUnit.assert['throws'];
-
-	// explicitly call `QUnit.module()` instead of `module()`
-	// in case we are in a CLI environment
-	QUnit.module('koi8-r');
-
-	test('koi8r.encode', function() {
-		equal(
-			koi8r.encode('\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F'),
-			'\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F',
-			'U+0000 to U+007F remain unchanged'
-		);
-		equal(
-			koi8r.encode(<%= decoded %>),
-			<%= encoded %>,
-			'Encoding all other symbols in the character set'
-		);
-		raises(
-			function() {
-				koi8r.encode('\uFFFF');
-			},
-			Error,
-			'Encoding a code point that is invalid for this encoding throws an error in `fatal` mode, which is the implied default for `encode()`'
-		);
-		raises(
-			function() {
-				koi8r.encode('\uFFFF', { 'mode': 'fatal' });
-			},
-			Error,
-			'Encoding a code point that is invalid for this encoding throws an error in `fatal` mode'
-		);
-		raises(
-			function() {
-				koi8r.encode('\uFFFF', { 'mode': 'FATAL' });
-			},
-			Error,
-			'Mode names are case-insensitive'
-		);
-		raises(
-			function() {
-				koi8r.encode('\uFFFF', { 'mode': 'fAtAl' });
-			},
-			Error,
-			'Mode names are case-insensitive'
-		);
-		equal(
-			koi8r.encode('\uFFFF', { 'mode': 'html' }),
-			'&#65535;',
-			'Encoding a code point that is invalid for this encoding returns an HTML entity in `html` mode'
-		);
-		equal(
-			koi8r.encode('\uFFFF', { 'mode': 'HTML' }),
-			'&#65535;',
-			'Mode names are case-insensitive'
-		);
-		equal(
-			koi8r.encode('\uFFFF', { 'mode': 'hTmL' }),
-			'&#65535;',
-			'Mode names are case-insensitive'
-		);
-	});
-
-	test('koi8r.decode', function() {
-		equal(
-			koi8r.decode('\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F'),
-			'\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F',
-			'U+0000 to U+007F remain unchanged'
-		);
-		equal(
-			koi8r.decode(<%= encoded %>),
-			<%= decoded %>,
-			'Decoding all other symbols in the character set'
-		);
-		equal(
-			koi8r.decode('\uFFFF'),
-			'\uFFFD',
-			'Decoding a byte that is invalid for this encoding returns U+FFFD in `replacement` mode, which is the implied default for `decode()`'
-		);
-		equal(
-			koi8r.decode('\uFFFF', { 'mode': 'replacement' }),
-			'\uFFFD',
-			'Decoding a byte that is invalid for this encoding returns U+FFFD in `replacement` mode'
-		);
-		equal(
-			koi8r.decode('\uFFFF', { 'mode': 'REPLACEMENT' }),
-			'\uFFFD',
-			'Mode names are case-insensitive'
-		);
-		equal(
-			koi8r.decode('\uFFFF', { 'mode': 'rEpLaCeMeNt' }),
-			'\uFFFD',
-			'Mode names are case-insensitive'
-		);
-		raises(
-			function() {
-				koi8r.decode('\uFFFF', { 'mode': 'fatal' });
-			},
-			Error,
-			'Decoding a byte that is invalid for this encoding throws an error in `fatal` mode'
-		);
-		raises(
-			function() {
-				koi8r.decode('\uFFFF', { 'mode': 'FATAL' });
-			},
-			Error,
-			'Decoding a byte that is invalid for this encoding throws an error in `fatal` mode'
-		);
-		raises(
-			function() {
-				koi8r.decode('\uFFFF', { 'mode': 'fAtAl' });
-			},
-			Error,
-			'Mode names are case-insensitive'
-		);
-	});
-
-	/*--------------------------------------------------------------------------*/
-
-	// configure QUnit and call `QUnit.start()` for
-	// Narwhal, Node.js, PhantomJS, Rhino, and RingoJS
-	if (!root.document || root.phantom) {
-		QUnit.config.noglobals = true;
-		QUnit.start();
-	}
-}(typeof global == 'object' && global || this));
+console.log('Testing `koi8r.decode`…');
+assert.strictEqual(
+	koi8r.decode('\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F'),
+	'\0\x01\x02\x03\x04\x05\x06\x07\b\t\n\x0B\f\r\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F !"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~\x7F',
+	'U+0000 to U+007F remain unchanged'
+);
+assert.strictEqual(
+	koi8r.decode(<%= encoded %>),
+	<%= decoded %>,
+	'Decoding all other symbols in the character set'
+);
+assert.strictEqual(
+	koi8r.decode('\uFFFF'),
+	'\uFFFD',
+	'Decoding a byte that is invalid for this encoding returns U+FFFD in `replacement` mode, which is the implied default for `decode()`'
+);
+assert.strictEqual(
+	koi8r.decode('\uFFFF', { mode: 'replacement' }),
+	'\uFFFD',
+	'Decoding a byte that is invalid for this encoding returns U+FFFD in `replacement` mode'
+);
+assert.strictEqual(
+	koi8r.decode('\uFFFF', { mode: 'REPLACEMENT' }),
+	'\uFFFD',
+	'Mode names are case-insensitive'
+);
+assert.strictEqual(
+	koi8r.decode('\uFFFF', { mode: 'rEpLaCeMeNt' }),
+	'\uFFFD',
+	'Mode names are case-insensitive'
+);
+assert.throws(
+	() => {
+		koi8r.decode('\uFFFF', { mode: 'fatal' });
+	},
+	Error,
+	'Decoding a byte that is invalid for this encoding throws an error in `fatal` mode'
+);
+assert.throws(
+	() => {
+		koi8r.decode('\uFFFF', { mode: 'FATAL' });
+	},
+	Error,
+	'Decoding a byte that is invalid for this encoding throws an error in `fatal` mode'
+);
+assert.throws(
+	() => {
+		koi8r.decode('\uFFFF', { mode: 'fAtAl' });
+	},
+	Error,
+	'Mode names are case-insensitive'
+);