wip: code formatting nits continued

test/nthArg.spec.js

@@ -0,0 +1,64 @@
+import lodashStable from 'lodash';
+import { args, falsey, stubA, stubB, noop } from './utils';
+import nthArg from '../src/nthArg';
+
+describe('nthArg', () => {
+    const args = ['a', 'b', 'c', 'd'];
+
+    it('should create a function that returns its nth argument', () => {
+        const actual = lodashStable.map(args, (value, index) => {
+            const func = nthArg(index);
+            return func.apply(undefined, args);
+        });
+
+        expect(actual).toEqual(args);
+    });
+
+    it('should work with a negative `n`', () => {
+        const actual = lodashStable.map(lodashStable.range(1, args.length + 1), (n) => {
+            const func = nthArg(-n);
+            return func.apply(undefined, args);
+        });
+
+        expect(actual, ['d', 'c', 'b').toEqual('a']);
+    });
+
+    it('should coerce `n` to an integer', () => {
+        let values = falsey;
+        let expected = lodashStable.map(values, stubA);
+
+        let actual = lodashStable.map(values, (n) => {
+            const func = n ? nthArg(n) : nthArg();
+            return func.apply(undefined, args);
+        });
+
+        expect(actual).toEqual(expected);
+
+        values = ['1', 1.6];
+        expected = lodashStable.map(values, stubB);
+
+        actual = lodashStable.map(values, (n) => {
+            const func = nthArg(n);
+            return func.apply(undefined, args);
+        });
+
+        expect(actual).toEqual(expected);
+    });
+
+    it('should return `undefined` for empty arrays', () => {
+        const func = nthArg(1);
+        expect(func()).toBe(undefined);
+    });
+
+    it('should return `undefined` for non-indexes', () => {
+        const values = [Infinity, args.length];
+        const expected = lodashStable.map(values, noop);
+
+        const actual = lodashStable.map(values, (n) => {
+            const func = nthArg(n);
+            return func.apply(undefined, args);
+        });
+
+        expect(actual).toEqual(expected);
+    });
+});