wip: code formatting nits continued

test/isFunction.spec.js

@@ -0,0 +1,80 @@
+import lodashStable from 'lodash';
+
+import {
+    slice,
+    asyncFunc,
+    genFunc,
+    arrayViews,
+    objToString,
+    funcTag,
+    falsey,
+    stubFalse,
+    args,
+    symbol,
+    document,
+    realm,
+} from './utils';
+
+import isFunction from '../src/isFunction';
+
+describe('isFunction', () => {
+    it('should return `true` for functions', () => {
+        expect(isFunction(slice)).toBe(true);
+    });
+
+    it('should return `true` for async functions', () => {
+        expect(isFunction(asyncFunc)).toBe(typeof asyncFunc === 'function');
+    });
+
+    it('should return `true` for generator functions', () => {
+        expect(isFunction(genFunc)).toBe(typeof genFunc === 'function');
+    });
+
+    it('should return `true` for the `Proxy` constructor', () => {
+        if (Proxy) {
+            expect(isFunction(Proxy)).toBe(true);
+        }
+    });
+
+    it('should return `true` for array view constructors', () => {
+        const expected = lodashStable.map(
+            arrayViews,
+            (type) => objToString.call(root[type]) === funcTag,
+        );
+
+        const actual = lodashStable.map(arrayViews, (type) => isFunction(root[type]));
+
+        expect(actual).toEqual(expected);
+    });
+
+    it('should return `false` for non-functions', () => {
+        const expected = lodashStable.map(falsey, stubFalse);
+
+        const actual = lodashStable.map(falsey, (value, index) =>
+            index ? isFunction(value) : isFunction(),
+        );
+
+        expect(actual).toEqual(expected);
+
+        expect(isFunction(args)).toBe(false);
+        expect(isFunction([1, 2, 3])).toBe(false);
+        expect(isFunction(true)).toBe(false);
+        expect(isFunction(new Date())).toBe(false);
+        expect(isFunction(new Error())).toBe(false);
+        expect(isFunction({ a: 1 })).toBe(false);
+        expect(isFunction(1)).toBe(false);
+        expect(isFunction(/x/)).toBe(false);
+        expect(isFunction('a')).toBe(false);
+        expect(isFunction(symbol)).toBe(false);
+
+        if (document) {
+            expect(isFunction(document.getElementsByTagName('body'))).toBe(false);
+        }
+    });
+
+    it('should work with a function from another realm', () => {
+        if (realm.function) {
+            expect(isFunction(realm.function)).toBe(true);
+        }
+    });
+});