Structure fixtures so they can be easily tested for exclusivity (#215)

source/index.ts

@@ -11,6 +11,7 @@ import type {
 	WeakRef,
 	Whitespace,
 } from './types.js';
+import {keysOf} from './utilities.js';
 
 // From type-fest.
 type ExtractFromGlobalConstructors<Name extends string> =
@@ -209,10 +210,14 @@ function detect(value: unknown): TypeName {
 	}
 
 	const tagType = getObjectType(value);
-	if (tagType) {
+	if (tagType && tagType !== 'Object') {
 		return tagType;
 	}
 
+	if (hasPromiseApi(value)) {
+		return 'Promise';
+	}
+
 	if (value instanceof String || value instanceof Boolean || value instanceof Number) {
 		throw new TypeError('Please don\'t use object wrappers for primitive types');
 	}
@@ -1120,10 +1125,6 @@ const methodTypeMap = {
 	isWhitespaceString: 'whitespace string',
 } as const;
 
-function keysOf<T extends Record<PropertyKey, unknown>>(value: T): Array<keyof T> {
-	return Object.keys(value) as Array<keyof T>;
-}
-
 type IsMethodName = keyof typeof methodTypeMap;
 const isMethodNames: IsMethodName[] = keysOf(methodTypeMap);
 

source/utilities.ts

@@ -0,0 +1,3 @@
+export function keysOf<T extends Record<PropertyKey, unknown>>(value: T): Array<keyof T> {
+	return Object.keys(value) as Array<keyof T>;
+}