diff --git a/src/common/all_test.ts b/src/common/all_test.ts
index 77e7f22..1fe3b29 100644
--- a/src/common/all_test.ts
+++ b/src/common/all_test.ts
@@ -19,371 +19,423 @@ const {
 	testSuite,
 } = await getTestRunner();
 
+const ANSITest = {
+	'moveCursor()': () => {
+		assertEquals(Ansi.moveCursor(1, 2), '\x1b[2;3H');
+	},
+	'moveCursorForward()': () => {
+		assertEquals(Ansi.moveCursorForward(2), '\x1b[2C');
+	},
+	'moveCursorDown()': () => {
+		assertEquals(Ansi.moveCursorDown(7), '\x1b[7B');
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const BufferTest = {
+	'new Buffer': () => {
+		const b = new Buffer();
+		assertInstanceOf(b, Buffer);
+		assertEquals(b.strlen(), 0);
+	},
+	'.appendLine': () => {
+		const b = new Buffer();
+
+		// Carriage return and line feed
+		b.appendLine();
+		assertEquals(b.strlen(), 2);
+
+		b.clear();
+		assertEquals(b.strlen(), 0);
+
+		b.appendLine('foo');
+		assertEquals(b.strlen(), 5);
+	},
+	'.append': () => {
+		const b = new Buffer();
+
+		b.append('foobar');
+		assertEquals(b.strlen(), 6);
+		b.clear();
+
+		b.append('foobar', 3);
+		assertEquals(b.strlen(), 3);
+	},
+	'.flush': async () => {
+		const b = new Buffer();
+		b.appendLine('foobarbaz' + Ansi.ClearLine);
+		assertEquals(b.strlen(), 14);
+
+		await b.flush();
+
+		assertEquals(b.strlen(), 0);
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const DocumentTest = {
+	'.default': () => {
+		const doc = Document.default();
+		assertEquals(doc.numRows, 0);
+		assertTrue(doc.isEmpty());
+		assertEquals(doc.row(0), null);
+	},
+	'.insertRow': () => {
+		const doc = Document.default();
+		doc.insertRow(undefined, 'foobar');
+		assertEquals(doc.numRows, 1);
+		assertFalse(doc.isEmpty());
+		assertInstanceOf(doc.row(0), Row);
+	},
+	'.insert': () => {
+		const doc = Document.default();
+		assertFalse(doc.dirty);
+		doc.insert(Position.at(0, 0), 'foobar');
+		assertEquals(doc.numRows, 1);
+		assertTrue(doc.dirty);
+
+		doc.insert(Position.at(2, 0), 'baz');
+		assertEquals(doc.numRows, 1);
+		assertTrue(doc.dirty);
+
+		doc.insert(Position.at(9, 0), 'buzz');
+		assertEquals(doc.numRows, 1);
+		assertTrue(doc.dirty);
+		const row0 = doc.row(0);
+		assertEquals(row0?.toString(), 'foobazbarbuzz');
+		assertEquals(row0?.rstring(), 'foobazbarbuzz');
+		assertEquals(row0?.rsize, 13);
+
+		doc.insert(Position.at(0, 1), 'Lorem Ipsum');
+		assertEquals(doc.numRows, 2);
+		assertTrue(doc.dirty);
+	},
+	'.delete': () => {
+		const doc = Document.default();
+		doc.insert(Position.default(), 'foobar');
+		doc.delete(Position.at(3, 0));
+		assertEquals(doc.row(0)?.toString(), 'fooar');
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const EditorTest = {
+	'new Editor': () => {
+		const e = new Editor(defaultTerminalSize);
+		assertInstanceOf(e, Editor);
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const PositionTest = {
+	'.default': () => {
+		const p = Position.default();
+		assertEquals(p.x, 0);
+		assertEquals(p.y, 0);
+	},
+	'.at': () => {
+		const p = Position.at(5, 7);
+		assertEquals(p.x, 5);
+		assertEquals(p.y, 7);
+	},
+	'.from': () => {
+		const p1 = Position.at(1, 2);
+		const p2 = Position.from(p1);
+
+		p1.x = 2;
+		p1.y = 4;
+
+		assertEquals(p1.x, 2);
+		assertEquals(p1.y, 4);
+
+		assertEquals(p2.x, 1);
+		assertEquals(p2.y, 2);
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const RowTest = {
+	'.default': () => {
+		const row = Row.default();
+		assertEquals(row.toString(), '');
+	},
+	'.from': () => {
+		// From string
+		const row = Row.from('xyz');
+		assertEquals(row.toString(), 'xyz');
+
+		// From existing Row
+		assertEquals(Row.from(row).toString(), row.toString());
+
+		// From 'chars'
+		assertEquals(Row.from(['😺', '😸', '😹']).toString(), '😺😸😹');
+	},
+	'.append': () => {
+		const row = Row.from('foo');
+		row.append('bar');
+		assertEquals(row.toString(), 'foobar');
+	},
+	'.delete': () => {
+		const row = Row.from('foof');
+		row.delete(3);
+		assertEquals(row.toString(), 'foo');
+
+		row.delete(4);
+		assertEquals(row.toString(), 'foo');
+	},
+	'.split': () => {
+		// When you split a row, it's from the cursor position
+		// (Kind of like if the string were one-indexed)
+		const row = Row.from('foobar');
+		const row2 = Row.from('bar');
+		assertEquals(row.split(3).toString(), row2.toString());
+	},
+	'.find': () => {
+		const normalRow = Row.from('For whom the bell tolls');
+		assertEquals(normalRow.find('who'), 4);
+		assertNull(normalRow.find('foo'));
+
+		const emojiRow = Row.from('😺😸😹');
+		assertEquals(emojiRow.find('😹'), 2);
+		assertNull(emojiRow.find('🤰🏼'));
+	},
+	'.byteIndexToCharIndex': () => {
+		// Each 'character' is two bytes
+		const row = Row.from('😺😸😹👨‍👩‍👧‍👦');
+		assertEquals(row.byteIndexToCharIndex(4), 2);
+		assertEquals(row.byteIndexToCharIndex(2), 1);
+		assertEquals(row.byteIndexToCharIndex(0), 0);
+
+		// Return count on nonsense index
+		assertEquals(Fn.strlen(row.toString()), 10);
+		assertEquals(row.byteIndexToCharIndex(72), 10);
+
+		const row2 = Row.from('foobar');
+		assertEquals(row2.byteIndexToCharIndex(2), 2);
+	},
+	'.charIndexToByteIndex': () => {
+		// Each 'character' is two bytes
+		const row = Row.from('😺😸😹👨‍👩‍👧‍👦');
+		assertEquals(row.charIndexToByteIndex(2), 4);
+		assertEquals(row.charIndexToByteIndex(1), 2);
+		assertEquals(row.charIndexToByteIndex(0), 0);
+	},
+	'.cxToRx, .rxToCx': () => {
+		const row = Row.from('foo\tbar\tbaz');
+		row.update();
+		assertNotEquals(row.chars, row.rchars);
+		assertNotEquals(row.size, row.rsize);
+		assertEquals(row.size, 11);
+		assertEquals(row.rsize, row.size + (SCROLL_TAB_SIZE * 2) - 2);
+
+		const cx = 11;
+		const aRx = row.cxToRx(cx);
+		const rx = 11;
+		const aCx = row.rxToCx(aRx);
+		assertEquals(aCx, cx);
+		assertEquals(aRx, rx);
+	},
+};
+
+// ----------------------------------------------------------------------------
+
+const fnTest = {
+	'defined()': () => {
+		const { defined } = Fn;
+		assertFalse(defined(null));
+		assertFalse(defined(void 0));
+		assertFalse(defined(undefined));
+		assertTrue(defined(0));
+		assertTrue(defined(false));
+	},
+	'nullish()': () => {
+		const { nullish } = Fn;
+
+		assertTrue(nullish(null));
+		assertTrue(nullish(void 0));
+		assertTrue(nullish(undefined));
+		assertFalse(nullish(0));
+		assertFalse(nullish(false));
+	},
+	'arrayInsert() strings': () => {
+		const { arrayInsert } = Fn;
+
+		const a = ['😺', '😸', '😹'];
+		const b = arrayInsert(a, 1, 'x');
+		const c = ['😺', 'x', '😸', '😹'];
+		assertEquals(b, c);
+
+		const d = arrayInsert(c, 17, 'y');
+		const e = ['😺', 'x', '😸', '😹', 'y'];
+		assertEquals(d, e);
+
+		assertEquals(arrayInsert([], 0, 'foo'), ['foo']);
+	},
+	'arrayInsert() numbers': () => {
+		const { arrayInsert } = Fn;
+
+		const a = [1, 3, 5];
+		const b = [1, 3, 4, 5];
+		assertEquals(arrayInsert(a, 2, 4), b);
+
+		const c = [1, 2, 3, 4, 5];
+		assertEquals(arrayInsert(b, 1, 2), c);
+	},
+	'noop fn': () => {
+		assertExists(Fn.noop);
+		assertEquals(Fn.noop(), undefined);
+	},
+	'posSub()': () => {
+		assertEquals(Fn.posSub(14, 15), 0);
+		assertEquals(Fn.posSub(15, 1), 14);
+	},
+	'minSub()': () => {
+		assertEquals(Fn.minSub(13, 25, -1), -1);
+		assertEquals(Fn.minSub(25, 13, 0), 12);
+	},
+	'maxAdd()': () => {
+		assertEquals(Fn.maxAdd(99, 99, 75), 75);
+		assertEquals(Fn.maxAdd(25, 74, 101), 99);
+	},
+	'ord()': () => {
+		const { ord } = Fn;
+
+		// Invalid output
+		assertEquals(ord(''), 256);
+
+		// Valid output
+		assertEquals(ord('a'), 97);
+	},
+	'strChars() properly splits strings into unicode characters': () => {
+		const { strChars } = Fn;
+
+		assertEquals(strChars('😺😸😹'), ['😺', '😸', '😹']);
+	},
+	'ctrlKey()': () => {
+		const { ctrlKey, isControl } = Fn;
+
+		const ctrl_a = ctrlKey('a');
+		assertTrue(isControl(ctrl_a));
+		assertEquals(ctrl_a, String.fromCodePoint(0x01));
+
+		const invalid = ctrlKey('😺');
+		assertFalse(isControl(invalid));
+		assertEquals(invalid, '😺');
+	},
+	'isAscii()': () => {
+		const { isAscii } = Fn;
+
+		assertTrue(isAscii('asjyverkjhsdf1928374'));
+		assertFalse(isAscii('😺acalskjsdf'));
+		assertFalse(isAscii('ab😺ac'));
+	},
+	'isAsciiDigit()': () => {
+		const { isAsciiDigit } = Fn;
+
+		assertTrue(isAsciiDigit('1234567890'));
+		assertFalse(isAsciiDigit('A1'));
+		assertFalse(isAsciiDigit('/'));
+		assertFalse(isAsciiDigit(':'));
+	},
+	'isControl()': () => {
+		const { isControl } = Fn;
+
+		assertFalse(isControl('abc'));
+		assertTrue(isControl(String.fromCodePoint(0x01)));
+		assertFalse(isControl('😺'));
+	},
+	'strlen()': () => {
+		const { strlen } = Fn;
+
+		// Ascii length
+		assertEquals(strlen('abc'), 'abc'.length);
+
+		// Get number of visible unicode characters
+		assertEquals(strlen('😺😸😹'), 3);
+		assertNotEquals('😺😸😹'.length, strlen('😺😸😹'));
+
+		// Skin tone modifier + base character
+		assertEquals(strlen('🤰🏼'), 2);
+		assertNotEquals('🤰🏼'.length, strlen('🤰🏼'));
+
+		// This has 4 sub-characters, and 3 zero-width-joiners
+		assertEquals(strlen('👨‍👩‍👧‍👦'), 7);
+		assertNotEquals('👨‍👩‍👧‍👦'.length, strlen('👨‍👩‍👧‍👦'));
+	},
+	'truncate()': () => {
+		const { truncate } = Fn;
+
+		assertEquals(truncate('😺😸😹', 1), '😺');
+		assertEquals(truncate('😺😸😹', 5), '😺😸😹');
+		assertEquals(truncate('👨‍👩‍👧‍👦', 5), '👨‍👩‍👧');
+	},
+};
+
+// ----------------------------------------------------------------------------
+
 const encoder = new TextEncoder();
+
 const testKeyMap = (codes: string[], expected: string) => {
 	codes.forEach((code) => {
 		assertEquals(Fn.readKey(encoder.encode(code)), expected);
 	});
 };
 
+const readKeyTest = {
+	'empty input': () => {
+		assertEquals(Fn.readKey(new Uint8Array(0)), '');
+	},
+	'passthrough': () => {
+		// Ignore unhandled escape sequences
+		assertEquals(Fn.readKey(encoder.encode('\x1b[]')), '\x1b[]');
+
+		// Pass explicitly mapped values right through
+		assertEquals(
+			Fn.readKey(encoder.encode(KeyCommand.ArrowUp)),
+			KeyCommand.ArrowUp,
+		);
+		assertEquals(
+			Fn.readKey(encoder.encode(KeyCommand.Home)),
+			KeyCommand.Home,
+		);
+		assertEquals(
+			Fn.readKey(encoder.encode(KeyCommand.Delete)),
+			KeyCommand.Delete,
+		);
+
+		// And pass through whatever else
+		assertEquals(Fn.readKey(encoder.encode('foobaz')), 'foobaz');
+	},
+
+	'Esc': () => testKeyMap(['\x1b', Fn.ctrlKey('l')], KeyCommand.Escape),
+	'Backspace': () =>
+		testKeyMap(
+			[Fn.ctrlKey('h'), '\x7f'],
+			KeyCommand.Backspace,
+		),
+	'Home': () =>
+		testKeyMap(['\x1b[1~', '\x1b[7~', '\x1b[H', '\x1bOH'], KeyCommand.Home),
+	'End': () =>
+		testKeyMap(['\x1b[4~', '\x1b[8~', '\x1b[F', '\x1bOF'], KeyCommand.End),
+	'Enter': () => testKeyMap(['\n', '\r', '\v'], KeyCommand.Enter),
+};
+
+// ----------------------------------------------------------------------------
+// Test Suite Setup
+// ----------------------------------------------------------------------------
+
 testSuite({
-	'ANSI utils': {
-		'moveCursor()': () => {
-			assertEquals(Ansi.moveCursor(1, 2), '\x1b[2;3H');
-		},
-		'moveCursorForward()': () => {
-			assertEquals(Ansi.moveCursorForward(2), '\x1b[2C');
-		},
-		'moveCursorDown()': () => {
-			assertEquals(Ansi.moveCursorDown(7), '\x1b[7B');
-		},
-	},
-	Buffer: {
-		'new Buffer': () => {
-			const b = new Buffer();
-			assertInstanceOf(b, Buffer);
-			assertEquals(b.strlen(), 0);
-		},
-		'.appendLine': () => {
-			const b = new Buffer();
-
-			// Carriage return and line feed
-			b.appendLine();
-			assertEquals(b.strlen(), 2);
-
-			b.clear();
-			assertEquals(b.strlen(), 0);
-
-			b.appendLine('foo');
-			assertEquals(b.strlen(), 5);
-		},
-		'.append': () => {
-			const b = new Buffer();
-
-			b.append('foobar');
-			assertEquals(b.strlen(), 6);
-			b.clear();
-
-			b.append('foobar', 3);
-			assertEquals(b.strlen(), 3);
-		},
-		'.flush': async () => {
-			const b = new Buffer();
-			b.appendLine('foobarbaz' + Ansi.ClearLine);
-			assertEquals(b.strlen(), 14);
-
-			await b.flush();
-
-			assertEquals(b.strlen(), 0);
-		},
-	},
-	Document: {
-		'.default': () => {
-			const doc = Document.default();
-			assertEquals(doc.numRows, 0);
-			assertTrue(doc.isEmpty());
-			assertEquals(doc.row(0), null);
-		},
-		'.insertRow': () => {
-			const doc = Document.default();
-			doc.insertRow(undefined, 'foobar');
-			assertEquals(doc.numRows, 1);
-			assertFalse(doc.isEmpty());
-			assertInstanceOf(doc.row(0), Row);
-		},
-		'.insert': () => {
-			const doc = Document.default();
-			assertFalse(doc.dirty);
-			doc.insert(Position.at(0, 0), 'foobar');
-			assertEquals(doc.numRows, 1);
-			assertTrue(doc.dirty);
-
-			doc.insert(Position.at(2, 0), 'baz');
-			assertEquals(doc.numRows, 1);
-			assertTrue(doc.dirty);
-
-			doc.insert(Position.at(9, 0), 'buzz');
-			assertEquals(doc.numRows, 1);
-			assertTrue(doc.dirty);
-			const row0 = doc.row(0);
-			assertEquals(row0?.toString(), 'foobazbarbuzz');
-			assertEquals(row0?.rstring(), 'foobazbarbuzz');
-			assertEquals(row0?.rsize, 13);
-
-			doc.insert(Position.at(0, 1), 'Lorem Ipsum');
-			assertEquals(doc.numRows, 2);
-			assertTrue(doc.dirty);
-		},
-		'.delete': () => {
-			const doc = Document.default();
-			doc.insert(Position.default(), 'foobar');
-			doc.delete(Position.at(3, 0));
-			assertEquals(doc.row(0)?.toString(), 'fooar');
-		},
-	},
-	Editor: {
-		'new Editor': () => {
-			const e = new Editor(defaultTerminalSize);
-			assertInstanceOf(e, Editor);
-		},
-	},
-	Position: {
-		'.default': () => {
-			const p = Position.default();
-			assertEquals(p.x, 0);
-			assertEquals(p.y, 0);
-		},
-		'.at': () => {
-			const p = Position.at(5, 7);
-			assertEquals(p.x, 5);
-			assertEquals(p.y, 7);
-		},
-		'.from': () => {
-			const p1 = Position.at(1, 2);
-			const p2 = Position.from(p1);
-
-			p1.x = 2;
-			p1.y = 4;
-
-			assertEquals(p1.x, 2);
-			assertEquals(p1.y, 4);
-
-			assertEquals(p2.x, 1);
-			assertEquals(p2.y, 2);
-		},
-	},
-	Row: {
-		'.default': () => {
-			const row = Row.default();
-			assertEquals(row.toString(), '');
-		},
-		'.from': () => {
-			// From string
-			const row = Row.from('xyz');
-			assertEquals(row.toString(), 'xyz');
-
-			// From existing Row
-			assertEquals(Row.from(row).toString(), row.toString());
-
-			// From 'chars'
-			assertEquals(Row.from(['😺', '😸', '😹']).toString(), '😺😸😹');
-		},
-		'.append': () => {
-			const row = Row.from('foo');
-			row.append('bar');
-			assertEquals(row.toString(), 'foobar');
-		},
-		'.delete': () => {
-			const row = Row.from('foof');
-			row.delete(3);
-			assertEquals(row.toString(), 'foo');
-
-			row.delete(4);
-			assertEquals(row.toString(), 'foo');
-		},
-		'.split': () => {
-			// When you split a row, it's from the cursor position
-			// (Kind of like if the string were one-indexed)
-			const row = Row.from('foobar');
-			const row2 = Row.from('bar');
-			assertEquals(row.split(3).toString(), row2.toString());
-		},
-		'.find': () => {
-			const normalRow = Row.from('For whom the bell tolls');
-			assertEquals(normalRow.find('who'), 4);
-			assertNull(normalRow.find('foo'));
-
-			const emojiRow = Row.from('😺😸😹');
-			assertEquals(emojiRow.find('😹'), 2);
-			assertNull(emojiRow.find('🤰🏼'));
-		},
-		'.byteIndexToCharIndex': () => {
-			// Each 'character' is two bytes
-			const row = Row.from('😺😸😹👨‍👩‍👧‍👦');
-			assertEquals(row.byteIndexToCharIndex(4), 2);
-			assertEquals(row.byteIndexToCharIndex(2), 1);
-			assertEquals(row.byteIndexToCharIndex(0), 0);
-
-			// Return count on nonsense index
-			assertEquals(Fn.strlen(row.toString()), 10);
-			assertEquals(row.byteIndexToCharIndex(72), 10);
-
-			const row2 = Row.from('foobar');
-			assertEquals(row2.byteIndexToCharIndex(2), 2);
-		},
-		'.charIndexToByteIndex': () => {
-			// Each 'character' is two bytes
-			const row = Row.from('😺😸😹👨‍👩‍👧‍👦');
-			assertEquals(row.charIndexToByteIndex(2), 4);
-			assertEquals(row.charIndexToByteIndex(1), 2);
-			assertEquals(row.charIndexToByteIndex(0), 0);
-		},
-		'.cxToRx, .rxToCx': () => {
-			const row = Row.from('foo\tbar\tbaz');
-			row.update();
-			assertNotEquals(row.chars, row.rchars);
-			assertNotEquals(row.size, row.rsize);
-			assertEquals(row.size, 11);
-			assertEquals(row.rsize, row.size + (SCROLL_TAB_SIZE * 2) - 2);
-
-			const cx = 11;
-			const aRx = row.cxToRx(cx);
-			const rx = 11;
-			const aCx = row.rxToCx(aRx);
-			assertEquals(aCx, cx);
-			assertEquals(aRx, rx);
-		},
-	},
-	'fns': {
-		'arrayInsert() strings': () => {
-			const { arrayInsert } = Fn;
-
-			const a = ['😺', '😸', '😹'];
-			const b = arrayInsert(a, 1, 'x');
-			const c = ['😺', 'x', '😸', '😹'];
-			assertEquals(b, c);
-
-			const d = arrayInsert(c, 17, 'y');
-			const e = ['😺', 'x', '😸', '😹', 'y'];
-			assertEquals(d, e);
-
-			assertEquals(arrayInsert([], 0, 'foo'), ['foo']);
-		},
-		'arrayInsert() numbers': () => {
-			const { arrayInsert } = Fn;
-
-			const a = [1, 3, 5];
-			const b = [1, 3, 4, 5];
-			assertEquals(arrayInsert(a, 2, 4), b);
-
-			const c = [1, 2, 3, 4, 5];
-			assertEquals(arrayInsert(b, 1, 2), c);
-		},
-		'noop fn': () => {
-			assertExists(Fn.noop);
-			assertEquals(Fn.noop(), undefined);
-		},
-		'posSub()': () => {
-			assertEquals(Fn.posSub(14, 15), 0);
-			assertEquals(Fn.posSub(15, 1), 14);
-		},
-		'minSub()': () => {
-			assertEquals(Fn.minSub(13, 25, -1), -1);
-			assertEquals(Fn.minSub(25, 13, 0), 12);
-		},
-		'maxAdd()': () => {
-			assertEquals(Fn.maxAdd(99, 99, 75), 75);
-			assertEquals(Fn.maxAdd(25, 74, 101), 99);
-		},
-		'ord()': () => {
-			const { ord } = Fn;
-
-			// Invalid output
-			assertEquals(ord(''), 256);
-
-			// Valid output
-			assertEquals(ord('a'), 97);
-		},
-		'strChars() properly splits strings into unicode characters': () => {
-			const { strChars } = Fn;
-
-			assertEquals(strChars('😺😸😹'), ['😺', '😸', '😹']);
-		},
-		'ctrlKey()': () => {
-			const { ctrlKey, isControl } = Fn;
-
-			const ctrl_a = ctrlKey('a');
-			assertTrue(isControl(ctrl_a));
-			assertEquals(ctrl_a, String.fromCodePoint(0x01));
-
-			const invalid = ctrlKey('😺');
-			assertFalse(isControl(invalid));
-			assertEquals(invalid, '😺');
-		},
-		'isAscii()': () => {
-			const { isAscii } = Fn;
-
-			assertTrue(isAscii('asjyverkjhsdf1928374'));
-			assertFalse(isAscii('😺acalskjsdf'));
-			assertFalse(isAscii('ab😺ac'));
-		},
-		'isAsciiDigit()': () => {
-			const { isAsciiDigit } = Fn;
-
-			assertTrue(isAsciiDigit('1234567890'));
-			assertFalse(isAsciiDigit('A1'));
-			assertFalse(isAsciiDigit('/'));
-			assertFalse(isAsciiDigit(':'));
-		},
-		'isControl()': () => {
-			const { isControl } = Fn;
-
-			assertFalse(isControl('abc'));
-			assertTrue(isControl(String.fromCodePoint(0x01)));
-			assertFalse(isControl('😺'));
-		},
-		'strlen()': () => {
-			const { strlen } = Fn;
-
-			// Ascii length
-			assertEquals(strlen('abc'), 'abc'.length);
-
-			// Get number of visible unicode characters
-			assertEquals(strlen('😺😸😹'), 3);
-			assertNotEquals('😺😸😹'.length, strlen('😺😸😹'));
-
-			// Skin tone modifier + base character
-			assertEquals(strlen('🤰🏼'), 2);
-			assertNotEquals('🤰🏼'.length, strlen('🤰🏼'));
-
-			// This has 4 sub-characters, and 3 zero-width-joiners
-			assertEquals(strlen('👨‍👩‍👧‍👦'), 7);
-			assertNotEquals('👨‍👩‍👧‍👦'.length, strlen('👨‍👩‍👧‍👦'));
-		},
-		'truncate()': () => {
-			const { truncate } = Fn;
-
-			assertEquals(truncate('😺😸😹', 1), '😺');
-			assertEquals(truncate('😺😸😹', 5), '😺😸😹');
-			assertEquals(truncate('👨‍👩‍👧‍👦', 5), '👨‍👩‍👧');
-		},
-	},
-	'readKey()': {
-		'empty input': () => {
-			assertEquals(Fn.readKey(new Uint8Array(0)), '');
-		},
-		'passthrough': () => {
-			// Ignore unhandled escape sequences
-			assertEquals(Fn.readKey(encoder.encode('\x1b[]')), '\x1b[]');
-
-			// Pass explicitly mapped values right through
-			assertEquals(
-				Fn.readKey(encoder.encode(KeyCommand.ArrowUp)),
-				KeyCommand.ArrowUp,
-			);
-			assertEquals(
-				Fn.readKey(encoder.encode(KeyCommand.Home)),
-				KeyCommand.Home,
-			);
-			assertEquals(
-				Fn.readKey(encoder.encode(KeyCommand.Delete)),
-				KeyCommand.Delete,
-			);
-
-			// And pass through whatever else
-			assertEquals(Fn.readKey(encoder.encode('foobaz')), 'foobaz');
-		},
-
-		'Esc': () => testKeyMap(['\x1b', Fn.ctrlKey('l')], KeyCommand.Escape),
-		'Backspace': () =>
-			testKeyMap(
-				[Fn.ctrlKey('h'), '\x7f'],
-				KeyCommand.Backspace,
-			),
-		'Home': () =>
-			testKeyMap(['\x1b[1~', '\x1b[7~', '\x1b[H', '\x1bOH'], KeyCommand.Home),
-		'End': () =>
-			testKeyMap(['\x1b[4~', '\x1b[8~', '\x1b[F', '\x1bOF'], KeyCommand.End),
-		'Enter': () => testKeyMap(['\n', '\r', '\v'], KeyCommand.Enter),
-	},
+	'ANSI utils': ANSITest,
+	Buffer: BufferTest,
+	Document: DocumentTest,
+	Editor: EditorTest,
+	Position: PositionTest,
+	Row: RowTest,
+	fns: fnTest,
+	'readKey()': readKeyTest,
 });
diff --git a/src/common/document.ts b/src/common/document.ts
index 75b5dcf..8d2cc7c 100644
--- a/src/common/document.ts
+++ b/src/common/document.ts
@@ -81,7 +81,7 @@ export class Document {
 			const row = this.#rows[potential.y];
 
 			// Okay, we have to take the Javascript string index (potential.x), convert
-			// it to the Row character index, and then convert that to the Row render index
+			// it to the Row 'character' index, and then convert that to the Row render index
 			// so that the highlighted color starts in the right place.
 			const start = row.cxToRx(row.byteIndexToCharIndex(potential.x));
 
diff --git a/src/common/fns.ts b/src/common/fns.ts
index 3180abc..14494a8 100644
--- a/src/common/fns.ts
+++ b/src/common/fns.ts
@@ -11,6 +11,20 @@ const decoder = new TextDecoder();
  */
 export const noop = () => {};
 
+/**
+ * Does a value exist? (not null or undefined)
+ */
+export function defined(v: unknown): boolean {
+	return v !== null && typeof v !== 'undefined';
+}
+
+/**
+ * Is the value null or undefined?
+ */
+export function nullish(v: unknown): boolean {
+	return v === null || typeof v === 'undefined';
+}
+
 /**
  * Convert input from ANSI escape sequences into a form
  * that can be more easily mapped to editor commands
diff --git a/src/common/row.ts b/src/common/row.ts
index d66f409..6d56be7 100644
--- a/src/common/row.ts
+++ b/src/common/row.ts
@@ -107,6 +107,9 @@ export class Row {
 		return this.byteIndexToCharIndex(byteCount);
 	}
 
+	/**
+	 * Convert the raw row offset to the equivalent offset for screen rendering
+	 */
 	public cxToRx(cx: number): number {
 		let rx = 0;
 		let j;
@@ -120,6 +123,9 @@ export class Row {
 		return rx;
 	}
 
+	/**
+	 * Convert the screen rendering row offset to the file row offset
+	 */
 	public rxToCx(rx: number): number {
 		let curRx = 0;
 		let cx = 0;
@@ -137,6 +143,10 @@ export class Row {
 		return cx;
 	}
 
+	/**
+	 * Convert the index of a JS string into the equivalent
+	 * 'unicode character' index
+	 */
 	public byteIndexToCharIndex(byteIndex: number): number {
 		if (this.toString().length === this.chars.length) {
 			return byteIndex;
@@ -154,6 +164,10 @@ export class Row {
 		return this.chars.length;
 	}
 
+	/**
+	 * Convert the 'unicode character' index into the equivalent
+	 * JS string index
+	 */
 	public charIndexToByteIndex(charIndex: number): number {
 		if (charIndex === 0 || this.toString().length === this.chars.length) {
 			return charIndex;