Meta tweaks

package.json

@@ -4,6 +4,7 @@
 	"description": "Type check values",
 	"license": "MIT",
 	"repository": "sindresorhus/is",
+	"funding": "https://github.com/sindresorhus/is?sponsor=1",
 	"author": {
 		"name": "Sindre Sorhus",
 		"email": "sindresorhus@gmail.com",

readme.md

@@ -6,7 +6,6 @@ For example, `is.string('🦄') //=> true`
 
 <img src="header.gif" width="182" align="right">
 
-
 ## Highlights
 
 - Written in TypeScript
@@ -15,14 +14,12 @@ For example, `is.string('🦄') //=> true`
 - Actively maintained
 - 2 million weekly downloads
 
-
 ## Install
 
 ```
 $ npm install @sindresorhus/is
 ```
 
-
 ## Usage
 
 ```js
@@ -38,15 +35,23 @@ is.number(6);
 //=> true
 ```
 
-[Assertions](#type-assertions) perform the same type checks, but throw errors if the type does not match.
+[Assertions](#type-assertions) perform the same type checks, but throw an error if the type does not match.
 
 ```js
 const {assert} = require('@sindresorhus/is');
 
-assert.string(foo);
+assert.string(2);
-// foo is known to be a string here
+//=> Error: Expected value which is `string`, received value of type `number`.
 ```
 
+And with TypeScript:
+
+```ts
+import {assert} from '@sindresorhus/is';
+
+assert.string(foo);
+// `foo` is now typed as a `string`.
+```
 
 ## API
 
@@ -406,7 +411,6 @@ is.all(is.string, '🦄', [], 'unicorns');
 //=> false
 ```
 
-
 ## Type guards
 
 When using `is` together with TypeScript, [type guards](http://www.typescriptlang.org/docs/handbook/advanced-types.html#type-guards-and-differentiating-types) are being used extensively to infer the correct type inside if-else statements.
@@ -437,18 +441,20 @@ padLeft('🦄', '🌈');
 
 ## Type assertions
 
-The type guards are also available as [typescript assertions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions), which throw an error for unexpected types. It is a convenient one-line version of the often repetitive "if-not-expected-type-throw" pattern.
+The type guards are also available as [type assertions](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions), which throw an error for unexpected types. It is a convenient one-line version of the often repetitive "if-not-expected-type-throw" pattern.
 
 ```ts
 import {assert} from '@sindresorhus/is';
 
 const handleMovieRatingApiResponse = (response: unknown) => {
 	assert.plainObject(response);
-	// `response` is typed as a plain `object` with `unknown` properties
+	// `response` is now typed as a plain `object` with `unknown` properties.
+
 	assert.number(response.rating);
-	// `response.rating` is typed as a `number`
+	// `response.rating` is now typed as a `number`.
+
 	assert.string(response.title);
-	// `response.title` is typed as a `string`
+	// `response.title` is now typed as a `string`.
 
 	return `${response.title} (${response.rating * 10})`;
 };
@@ -456,8 +462,8 @@ const handleMovieRatingApiResponse = (response: unknown) => {
 handleMovieRatingApiResponse({rating: 0.87, title: 'The Matrix'});
 //=> 'The Matrix (8.7)'
 
-handleMovieRatingApiResponse({status: 'system maintenance'});
+// This throws an error.
-//=> throws error
+handleMovieRatingApiResponse({rating: '🦄'});
 ```
 
 ## FAQ
@@ -477,14 +483,12 @@ For the ones I found, pick 3 of these.
 
 The most common mistakes I noticed in these modules was using `instanceof` for type checking, forgetting that functions are objects, and omitting `symbol` as a primitive.
 
-
 ## For enterprise
 
 Available as part of the Tidelift Subscription.
 
 The maintainers of @sindresorhus/is and thousands of other packages are working with Tidelift to deliver commercial support and maintenance for the open source dependencies you use to build your applications. Save time, reduce risk, and improve code health, while paying the maintainers of the exact dependencies you use. [Learn more.](https://tidelift.com/subscription/pkg/npm-sindresorhus-is?utm_source=npm-sindresorhus-is&utm_medium=referral&utm_campaign=enterprise&utm_term=repo)
 
-
 ## Related
 
 - [ow](https://github.com/sindresorhus/ow) - Function argument validation for humans
@@ -498,7 +502,6 @@ The maintainers of @sindresorhus/is and thousands of other packages are working
 - [is-blob](https://github.com/sindresorhus/is-blob) - Check if a value is a Blob - File-like object of immutable, raw data
 - [has-emoji](https://github.com/sindresorhus/has-emoji) - Check whether a string has any emoji
 
-
 ## Maintainers
 
 - [Sindre Sorhus](https://github.com/sindresorhus)

source/index.ts

@@ -387,7 +387,7 @@ is.all = (predicate: Predicate, ...values: unknown[]): boolean => predicateOnArr
 
 const assertType = (condition: boolean, description: string, value: unknown): asserts condition => {
 	if (!condition) {
-		throw new TypeError(`Expected value which is "${description}", received value of type ${is(value)}.`);
+		throw new TypeError(`Expected value which is \`${description}\`, received value of type \`${is(value)}\`.`);
 	}
 };
 

test/test.ts

@@ -1,14 +1,13 @@
+import fs = require('fs');
+import net = require('net');
+import Stream = require('stream');
 import {inspect} from 'util';
 import test, {ExecutionContext} from 'ava';
 import {JSDOM} from 'jsdom';
 import {Subject, Observable} from 'rxjs';
-import is, {assert, AssertionTypeDescription, TypeName} from '../source';
-
-import fs = require('fs');
-import net = require('net');
-import Stream = require('stream');
 import tempy = require('tempy');
 import ZenObservable = require('zen-observable');
+import is, {assert, AssertionTypeDescription, TypeName} from '../source';
 
 class PromiseSubclassFixture<T> extends Promise<T> {}
 class ErrorSubclassFixture extends Error {}
@@ -26,7 +25,7 @@ interface Test {
 }
 
 const invertAssertThrow = (description: string, fn: () => void | never, value: unknown): void | never => {
-	const expectedAssertErrorMessage = `Expected value which is "${description}", received value of type ${is(value)}.`;
+	const expectedAssertErrorMessage = `Expected value which is \`${description}\`, received value of type \`${is(value)}\`.`;
 
 	try {
 		fn();
@@ -555,8 +554,8 @@ const testType = (t: ExecutionContext, type: string, exclude?: string[]) => {
 
 		for (const fixture of fixtures) {
 			assertIs(testIs(fixture), `Value: ${inspect(fixture)}`);
-			const valueType = JSON.stringify(typeDescription ? typeDescription : typename);
+			const valueType = typeDescription ? typeDescription : typename;
-			assertAsserts(() => testAssert(fixture), `Expected value which is ${valueType}, received value of type ${is(fixture)}.`);
+			assertAsserts(() => testAssert(fixture), `Expected value which is \`${valueType!}\`, received value of type \`${is(fixture)}\`.`);
 
 			if (isTypeUnderTest && typename) {
 				t.is(is(fixture), typename);
@@ -597,8 +596,12 @@ test('is.numericString', t => {
 	testType(t, 'numericString');
 	t.false(is.numericString(''));
 	t.false(is.numericString(1));
-	t.throws(() => assert.numericString(''));
+	t.throws(() => {
-	t.throws(() => assert.numericString(1));
+		assert.numericString('');
+	});
+	t.throws(() => {
+		assert.numericString(1);
+	});
 });
 
 test('is.array', t => {
@@ -611,7 +614,10 @@ test('is.function', t => {
 
 test('is.boundFunction', t => {
 	t.false(is.boundFunction(function () {})); // eslint-disable-line prefer-arrow-callback
-	t.throws(() => assert.boundFunction(function () {})); // eslint-disable-line prefer-arrow-callback
+
+	t.throws(() => {
+		assert.boundFunction(function () {}); // eslint-disable-line prefer-arrow-callback
+	});
 });
 
 test('is.buffer', t => {
@@ -660,8 +666,11 @@ test('is.asyncFunction', t => {
 	if (is.asyncFunction(fixture)) {
 		// eslint-disable-next-line promise/prefer-await-to-then
 		t.true(is.function_(fixture().then));
-		// eslint-disable-next-line promise/prefer-await-to-then
+
-		t.notThrows(() => assert.function_(fixture().then));
+		t.notThrows(() => {
+			// eslint-disable-next-line promise/prefer-await-to-then
+			assert.function_(fixture().then);
+		});
 	}
 });
 
@@ -747,13 +756,21 @@ test('is.directInstanceOf', t => {
 
 	t.true(is.directInstanceOf(error, Error));
 	t.true(is.directInstanceOf(errorSubclass, ErrorSubclassFixture));
-	t.notThrows(() => assert.directInstanceOf(error, Error));
+	t.notThrows(() => {
-	t.notThrows(() => assert.directInstanceOf(errorSubclass, ErrorSubclassFixture));
+		assert.directInstanceOf(error, Error);
+	});
+	t.notThrows(() => {
+		assert.directInstanceOf(errorSubclass, ErrorSubclassFixture);
+	});
 
 	t.false(is.directInstanceOf(error, ErrorSubclassFixture));
 	t.false(is.directInstanceOf(errorSubclass, Error));
-	t.throws(() => assert.directInstanceOf(error, ErrorSubclassFixture));
+	t.throws(() => {
-	t.throws(() => assert.directInstanceOf(errorSubclass, Error));
+		assert.directInstanceOf(error, ErrorSubclassFixture);
+	});
+	t.throws(() => {
+		assert.directInstanceOf(errorSubclass, Error);
+	});
 });
 
 test('is.urlInstance', t => {
@@ -763,10 +780,18 @@ test('is.urlInstance', t => {
 	t.false(is.urlInstance(undefined));
 	t.false(is.urlInstance(null));
 
-	t.notThrows(() => assert.urlInstance(url));
+	t.notThrows(() => {
-	t.throws(() => assert.urlInstance({}));
+		assert.urlInstance(url);
-	t.throws(() => assert.urlInstance(undefined));
+	});
-	t.throws(() => assert.urlInstance(null));
+	t.throws(() => {
+		assert.urlInstance({});
+	});
+	t.throws(() => {
+		assert.urlInstance(undefined);
+	});
+	t.throws(() => {
+		assert.urlInstance(null);
+	});
 });
 
 test('is.urlString', t => {
@@ -777,11 +802,21 @@ test('is.urlString', t => {
 	t.false(is.urlString(undefined));
 	t.false(is.urlString(null));
 
-	t.notThrows(() => assert.urlString(url));
+	t.notThrows(() => {
-	t.throws(() => assert.urlString(new URL(url)));
+		assert.urlString(url);
-	t.throws(() => assert.urlString({}));
+	});
-	t.throws(() => assert.urlString(undefined));
+	t.throws(() => {
-	t.throws(() => assert.urlString(null));
+		assert.urlString(new URL(url));
+	});
+	t.throws(() => {
+		assert.urlString({});
+	});
+	t.throws(() => {
+		assert.urlString(undefined);
+	});
+	t.throws(() => {
+		assert.urlString(null);
+	});
 });
 
 test('is.truthy', t => {
@@ -795,16 +830,30 @@ test('is.truthy', t => {
 	// t.true(is.truthy(1n));
 	t.true(is.truthy(BigInt(1)));
 
-	t.notThrows(() => assert.truthy('unicorn'));
+	t.notThrows(() => {
-	t.notThrows(() => assert.truthy('🦄'));
+		assert.truthy('unicorn');
-	t.notThrows(() => assert.truthy(new Set()));
+	});
-	t.notThrows(() => assert.truthy(Symbol('🦄')));
+	t.notThrows(() => {
-	t.notThrows(() => assert.truthy(true));
+		assert.truthy('🦄');
-	t.notThrows(() => assert.truthy(1));
+	});
+	t.notThrows(() => {
+		assert.truthy(new Set());
+	});
+	t.notThrows(() => {
+		assert.truthy(Symbol('🦄'));
+	});
+	t.notThrows(() => {
+		assert.truthy(true);
+	});
+	t.notThrows(() => {
+		assert.truthy(1);
+	});
 
-	// Disabled until TS supports it for an ESnnnn target.
+	// TODO: Disabled until TS supports it for an ESnnnn target.
 	// t.notThrows(() => assert.truthy(1n));
-	t.notThrows(() => assert.truthy(BigInt(1)));
+	t.notThrows(() => {
+		assert.truthy(BigInt(1));
+	});
 });
 
 test('is.falsy', t => {
@@ -814,19 +863,33 @@ test('is.falsy', t => {
 	t.true(is.falsy(null));
 	t.true(is.falsy(undefined));
 	t.true(is.falsy(NaN));
-	// Disabled until TS supports it for an ESnnnn target.
+	// TODO: Disabled until TS supports it for an ESnnnn target.
 	// t.true(is.falsy(0n));
 	t.true(is.falsy(BigInt(0)));
 
-	t.notThrows(() => assert.falsy(false));
+	t.notThrows(() => {
-	t.notThrows(() => assert.falsy(0));
+		assert.falsy(false);
-	t.notThrows(() => assert.falsy(''));
+	});
-	t.notThrows(() => assert.falsy(null));
+	t.notThrows(() => {
-	t.notThrows(() => assert.falsy(undefined));
+		assert.falsy(0);
-	t.notThrows(() => assert.falsy(NaN));
+	});
-	// Disabled until TS supports it for an ESnnnn target.
+	t.notThrows(() => {
+		assert.falsy('');
+	});
+	t.notThrows(() => {
+		assert.falsy(null);
+	});
+	t.notThrows(() => {
+		assert.falsy(undefined);
+	});
+	t.notThrows(() => {
+		assert.falsy(NaN);
+	});
+	// TODO: Disabled until TS supports it for an ESnnnn target.
 	// t.notThrows(() => assert.falsy(0n));
-	t.notThrows(() => assert.falsy(BigInt(0)));
+	t.notThrows(() => {
+		assert.falsy(BigInt(0));
+	});
 });
 
 test('is.nan', t => {
@@ -852,24 +915,32 @@ test('is.primitive', t => {
 		// 6n
 	];
 
-	for (const el of primitives) {
+	for (const element of primitives) {
-		t.true(is.primitive(el));
+		t.true(is.primitive(element));
-		t.notThrows(() => assert.primitive(el));
+		t.notThrows(() => {
+			assert.primitive(element);
+		});
 	}
 });
 
 test('is.integer', t => {
 	testType(t, 'integer', ['number', 'safeInteger']);
 	t.false(is.integer(1.4));
-	t.throws(() => assert.integer(1.4));
+	t.throws(() => {
+		assert.integer(1.4);
+	});
 });
 
 test('is.safeInteger', t => {
 	testType(t, 'safeInteger', ['number', 'integer']);
 	t.false(is.safeInteger(2 ** 53));
 	t.false(is.safeInteger(-(2 ** 53)));
-	t.throws(() => assert.safeInteger(2 ** 53));
+	t.throws(() => {
-	t.throws(() => assert.safeInteger(-(2 ** 53)));
+		assert.safeInteger(2 ** 53);
+	});
+	t.throws(() => {
+		assert.safeInteger(-(2 ** 53));
+	});
 });
 
 test('is.plainObject', t => {
@@ -887,15 +958,33 @@ test('is.iterable', t => {
 	t.false(is.iterable(Infinity));
 	t.false(is.iterable({}));
 
-	t.notThrows(() => assert.iterable(''));
+	t.notThrows(() => {
-	t.notThrows(() => assert.iterable([]));
+		assert.iterable('');
-	t.notThrows(() => assert.iterable(new Map()));
+	});
-	t.throws(() => assert.iterable(null));
+	t.notThrows(() => {
-	t.throws(() => assert.iterable(undefined));
+		assert.iterable([]);
-	t.throws(() => assert.iterable(0));
+	});
-	t.throws(() => assert.iterable(NaN));
+	t.notThrows(() => {
-	t.throws(() => assert.iterable(Infinity));
+		assert.iterable(new Map());
-	t.throws(() => assert.iterable({}));
+	});
+	t.throws(() => {
+		assert.iterable(null);
+	});
+	t.throws(() => {
+		assert.iterable(undefined);
+	});
+	t.throws(() => {
+		assert.iterable(0);
+	});
+	t.throws(() => {
+		assert.iterable(NaN);
+	});
+	t.throws(() => {
+		assert.iterable(Infinity);
+	});
+	t.throws(() => {
+		assert.iterable({});
+	});
 });
 
 test('is.asyncIterable', t => {
@@ -910,16 +999,30 @@ test('is.asyncIterable', t => {
 	t.false(is.asyncIterable(Infinity));
 	t.false(is.asyncIterable({}));
 
-	t.notThrows(() => assert.asyncIterable({
+	t.notThrows(() => {
-		[Symbol.asyncIterator]: () => { }
+		assert.asyncIterable({
-	}));
+			[Symbol.asyncIterator]: () => { }
+		});
+	});
 
-	t.throws(() => assert.asyncIterable(null));
+	t.throws(() => {
-	t.throws(() => assert.asyncIterable(undefined));
+		assert.asyncIterable(null);
-	t.throws(() => assert.asyncIterable(0));
+	});
-	t.throws(() => assert.asyncIterable(NaN));
+	t.throws(() => {
-	t.throws(() => assert.asyncIterable(Infinity));
+		assert.asyncIterable(undefined);
-	t.throws(() => assert.asyncIterable({}));
+	});
+	t.throws(() => {
+		assert.asyncIterable(0);
+	});
+	t.throws(() => {
+		assert.asyncIterable(NaN);
+	});
+	t.throws(() => {
+		assert.asyncIterable(Infinity);
+	});
+	t.throws(() => {
+		assert.asyncIterable({});
+	});
 });
 
 test('is.class', t => {
@@ -932,7 +1035,10 @@ test('is.class', t => {
 
 	for (const classDeclaration of classDeclarations) {
 		t.true(is.class_(classDeclaration));
-		t.notThrows(() => assert.class_(classDeclaration));
+
+		t.notThrows(() => {
+			assert.class_(classDeclaration);
+		});
 	}
 });
 
@@ -952,16 +1058,25 @@ test('is.typedArray', t => {
 
 	for (const item of typedArrays) {
 		t.true(is.typedArray(item));
-		t.notThrows(() => assert.typedArray(item));
+
+		t.notThrows(() => {
+			assert.typedArray(item);
+		});
 	}
 
 	t.false(is.typedArray(new ArrayBuffer(1)));
 	t.false(is.typedArray([]));
 	t.false(is.typedArray({}));
 
-	t.throws(() => assert.typedArray(new ArrayBuffer(1)));
+	t.throws(() => {
-	t.throws(() => assert.typedArray([]));
+		assert.typedArray(new ArrayBuffer(1));
-	t.throws(() => assert.typedArray({}));
+	});
+	t.throws(() => {
+		assert.typedArray([]);
+	});
+	t.throws(() => {
+		assert.typedArray({});
+	});
 });
 
 test('is.arrayLike', t => {
@@ -977,15 +1092,27 @@ test('is.arrayLike', t => {
 	t.false(is.arrayLike(new Map()));
 
 	(function () {
-		t.notThrows(() => assert.arrayLike(arguments)); // eslint-disable-line prefer-rest-params
+		t.notThrows(() => {
+			assert.arrayLike(arguments); // eslint-disable-line prefer-rest-params
+		});
 	})();
 
-	t.notThrows(() => assert.arrayLike([]));
+	t.notThrows(() => {
-	t.notThrows(() => assert.arrayLike('unicorn'));
+		assert.arrayLike([]);
+	});
+	t.notThrows(() => {
+		assert.arrayLike('unicorn');
+	});
 
-	t.throws(() => assert.arrayLike({}));
+	t.throws(() => {
-	t.throws(() => assert.arrayLike(() => { }));
+		assert.arrayLike({});
-	t.throws(() => assert.arrayLike(new Map()));
+	});
+	t.throws(() => {
+		assert.arrayLike(() => {});
+	});
+	t.throws(() => {
+		assert.arrayLike(new Map());
+	});
 });
 
 test('is.inRange', t => {
@@ -1018,20 +1145,57 @@ test('is.inRange', t => {
 		is.inRange(0, [1, 2, 3]);
 	});
 
-	t.notThrows(() => assert.inRange(x, [0, 5]));
+	t.notThrows(() => {
-	t.notThrows(() => assert.inRange(x, [5, 0]));
+		assert.inRange(x, [0, 5]);
-	t.notThrows(() => assert.inRange(x, [-5, 5]));
+	});
-	t.notThrows(() => assert.inRange(x, [5, -5]));
-	t.throws(() => assert.inRange(x, [4, 8]));
-	t.notThrows(() => assert.inRange(-7, [-5, -10]));
-	t.notThrows(() => assert.inRange(-5, [-5, -10]));
-	t.notThrows(() => assert.inRange(-10, [-5, -10]));
 
-	t.notThrows(() => assert.inRange(x, 10));
+	t.notThrows(() => {
-	t.notThrows(() => assert.inRange(0, 0));
+		assert.inRange(x, [5, 0]);
-	t.notThrows(() => assert.inRange(-2, -3));
+	});
-	t.throws(() => assert.inRange(x, 2));
+
-	t.throws(() => assert.inRange(-3, -2));
+	t.notThrows(() => {
+		assert.inRange(x, [-5, 5]);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(x, [5, -5]);
+	});
+
+	t.throws(() => {
+		assert.inRange(x, [4, 8]);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(-7, [-5, -10]);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(-5, [-5, -10]);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(-10, [-5, -10]);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(x, 10);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(0, 0);
+	});
+
+	t.notThrows(() => {
+		assert.inRange(-2, -3);
+	});
+
+	t.throws(() => {
+		assert.inRange(x, 2);
+	});
+
+	t.throws(() => {
+		assert.inRange(-3, -2);
+	});
 
 	t.throws(() => {
 		assert.inRange(0, []);
@@ -1049,7 +1213,9 @@ test('is.inRange', t => {
 test('is.domElement', t => {
 	testType(t, 'domElement');
 	t.false(is.domElement({nodeType: 1, nodeName: 'div'}));
-	t.throws(() => assert.domElement({nodeType: 1, nodeName: 'div'}));
+	t.throws(() => {
+		assert.domElement({nodeType: 1, nodeName: 'div'});
+	});
 
 	const htmlTagNameToTypeName = {
 		div: 'HTMLDivElement',
@@ -1081,24 +1247,32 @@ test('is.infinite', t => {
 test('is.evenInteger', t => {
 	for (const el of [-6, 2, 4]) {
 		t.true(is.evenInteger(el));
-		t.notThrows(() => assert.evenInteger(el));
+		t.notThrows(() => {
+			assert.evenInteger(el);
+		});
 	}
 
 	for (const el of [-3, 1, 5]) {
 		t.false(is.evenInteger(el));
-		t.throws(() => assert.evenInteger(el));
+		t.throws(() => {
+			assert.evenInteger(el);
+		});
 	}
 });
 
 test('is.oddInteger', t => {
 	for (const el of [-5, 7, 13]) {
 		t.true(is.oddInteger(el));
-		t.notThrows(() => assert.oddInteger(el));
+		t.notThrows(() => {
+			assert.oddInteger(el);
+		});
 	}
 
 	for (const el of [-8, 8, 10]) {
 		t.false(is.oddInteger(el));
-		t.throws(() => assert.oddInteger(el));
+		t.throws(() => {
+			assert.oddInteger(el);
+		});
 	}
 });
 
@@ -1111,15 +1285,23 @@ test('is.nonEmptyArray', t => {
 	t.false(is.nonEmptyArray([]));
 	t.false(is.nonEmptyArray(new Array())); // eslint-disable-line @typescript-eslint/no-array-constructor
 
-	t.notThrows(() => assert.nonEmptyArray([1, 2, 3]));
+	t.notThrows(() => {
-	t.throws(() => assert.nonEmptyArray([]));
+		assert.nonEmptyArray([1, 2, 3]);
-	t.throws(() => assert.nonEmptyArray(new Array())); // eslint-disable-line @typescript-eslint/no-array-constructor
+	});
+	t.throws(() => {
+		assert.nonEmptyArray([]);
+	});
+	t.throws(() => {
+		assert.nonEmptyArray(new Array()); // eslint-disable-line @typescript-eslint/no-array-constructor
+	});
 });
 
 test('is.emptyString', t => {
 	testType(t, 'emptyString', ['string']);
 	t.false(is.emptyString('🦄'));
-	t.throws(() => assert.emptyString('🦄'));
+	t.throws(() => {
+		assert.emptyString('🦄');
+	});
 });
 
 test('is.nonEmptyString', t => {
@@ -1127,9 +1309,15 @@ test('is.nonEmptyString', t => {
 	t.false(is.nonEmptyString(String()));
 	t.true(is.nonEmptyString('🦄'));
 
-	t.throws(() => assert.nonEmptyString(''));
+	t.throws(() => {
-	t.throws(() => assert.nonEmptyString(String()));
+		assert.nonEmptyString('');
-	t.notThrows(() => assert.nonEmptyString('🦄'));
+	});
+	t.throws(() => {
+		assert.nonEmptyString(String());
+	});
+	t.notThrows(() => {
+		assert.nonEmptyString('🦄');
+	});
 });
 
 test('is.emptyStringOrWhitespace', t => {
@@ -1138,9 +1326,15 @@ test('is.emptyStringOrWhitespace', t => {
 	t.false(is.emptyStringOrWhitespace('🦄'));
 	t.false(is.emptyStringOrWhitespace('unicorn'));
 
-	t.notThrows(() => assert.emptyStringOrWhitespace('  '));
+	t.notThrows(() => {
-	t.throws(() => assert.emptyStringOrWhitespace('🦄'));
+		assert.emptyStringOrWhitespace('  ');
-	t.throws(() => assert.emptyStringOrWhitespace('unicorn'));
+	});
+	t.throws(() => {
+		assert.emptyStringOrWhitespace('🦄');
+	});
+	t.throws(() => {
+		assert.emptyStringOrWhitespace('unicorn');
+	});
 });
 
 test('is.emptyObject', t => {
@@ -1148,9 +1342,15 @@ test('is.emptyObject', t => {
 	t.true(is.emptyObject(new Object())); // eslint-disable-line no-new-object
 	t.false(is.emptyObject({unicorn: '🦄'}));
 
-	t.notThrows(() => assert.emptyObject({}));
+	t.notThrows(() => {
-	t.notThrows(() => assert.emptyObject(new Object())); // eslint-disable-line no-new-object
+		assert.emptyObject({});
-	t.throws(() => assert.emptyObject({unicorn: '🦄'}));
+	});
+	t.notThrows(() => {
+		assert.emptyObject(new Object()); // eslint-disable-line no-new-object
+	});
+	t.throws(() => {
+		assert.emptyObject({unicorn: '🦄'});
+	});
 });
 
 test('is.nonEmptyObject', t => {
@@ -1161,9 +1361,15 @@ test('is.nonEmptyObject', t => {
 	t.false(is.nonEmptyObject(new Object())); // eslint-disable-line no-new-object
 	t.true(is.nonEmptyObject({unicorn: '🦄'}));
 
-	t.throws(() => assert.nonEmptyObject({}));
+	t.throws(() => {
-	t.throws(() => assert.nonEmptyObject(new Object())); // eslint-disable-line no-new-object
+		assert.nonEmptyObject({});
-	t.notThrows(() => assert.nonEmptyObject({unicorn: '🦄'}));
+	});
+	t.throws(() => {
+		assert.nonEmptyObject(new Object()); // eslint-disable-line no-new-object
+	});
+	t.notThrows(() => {
+		assert.nonEmptyObject({unicorn: '🦄'});
+	});
 });
 
 test('is.emptySet', t => {
@@ -1173,11 +1379,15 @@ test('is.emptySet', t => {
 test('is.nonEmptySet', t => {
 	const tempSet = new Set();
 	t.false(is.nonEmptySet(tempSet));
-	t.throws(() => assert.nonEmptySet(tempSet));
+	t.throws(() => {
+		assert.nonEmptySet(tempSet);
+	});
 
 	tempSet.add(1);
 	t.true(is.nonEmptySet(tempSet));
-	t.notThrows(() => assert.nonEmptySet(tempSet));
+	t.notThrows(() => {
+		assert.nonEmptySet(tempSet);
+	});
 });
 
 test('is.emptyMap', t => {
@@ -1187,11 +1397,15 @@ test('is.emptyMap', t => {
 test('is.nonEmptyMap', t => {
 	const tempMap = new Map();
 	t.false(is.nonEmptyMap(tempMap));
-	t.throws(() => assert.nonEmptyMap(tempMap));
+	t.throws(() => {
+		assert.nonEmptyMap(tempMap);
+	});
 
 	tempMap.set('unicorn', '🦄');
 	t.true(is.nonEmptyMap(tempMap));
-	t.notThrows(() => assert.nonEmptyMap(tempMap));
+	t.notThrows(() => {
+		assert.nonEmptyMap(tempMap);
+	});
 });
 
 test('is.any', t => {
@@ -1208,10 +1422,21 @@ test('is.any', t => {
 		is.any(is.string);
 	});
 
-	t.notThrows(() => assert.any(is.string, {}, true, '🦄'));
+	t.notThrows(() => {
-	t.notThrows(() => assert.any(is.object, false, {}, 'unicorns'));
+		assert.any(is.string, {}, true, '🦄');
-	t.throws(() => assert.any(is.boolean, '🦄', [], 3));
+	});
-	t.throws(() => assert.any(is.integer, true, 'lol', {}));
+
+	t.notThrows(() => {
+		assert.any(is.object, false, {}, 'unicorns');
+	});
+
+	t.throws(() => {
+		assert.any(is.boolean, '🦄', [], 3);
+	});
+
+	t.throws(() => {
+		assert.any(is.integer, true, 'lol', {});
+	});
 
 	t.throws(() => {
 		assert.any(null as any, true);
@@ -1236,10 +1461,21 @@ test('is.all', t => {
 		is.all(is.string);
 	});
 
-	t.notThrows(() => assert.all(is.object, {}, new Set(), new Map()));
+	t.notThrows(() => {
-	t.notThrows(() => assert.all(is.boolean, true, false));
+		assert.all(is.object, {}, new Set(), new Map());
-	t.throws(() => assert.all(is.string, '🦄', []));
+	});
-	t.throws(() => assert.all(is.set, new Map(), {}));
+
+	t.notThrows(() => {
+		assert.all(is.boolean, true, false);
+	});
+
+	t.throws(() => {
+		assert.all(is.string, '🦄', []);
+	});
+
+	t.throws(() => {
+		assert.all(is.set, new Map(), {});
+	});
 
 	t.throws(() => {
 		assert.all(null as any, true);
@@ -1251,18 +1487,18 @@ test('is.all', t => {
 });
 
 test('assert', t => {
-	// Contrived test showing that typescript acknowledges the type assertion in assert.number().
+	// Contrived test showing that TypeScript acknowledges the type assertion in `assert.number()`.
-	// Real world usage includes asserting user input, but here we use a random number/string generator.
+	// Real--world usage includes asserting user input, but here we use a random number/string generator.
 	t.plan(2);
 
 	const getNumberOrStringRandomly = (): number | string => {
-		const rnd = Math.random();
+		const random = Math.random();
 
-		if (rnd < 0.5) {
+		if (random < 0.5) {
 			return 'sometimes this function returns text';
 		}
 
-		return rnd;
+		return random;
 	};
 
 	const canUseOnlyNumber = (badlyTypedArgument: any): number => {