Fix Jest error when spying on import

TypeError: Cannot set property expand of #<Object> which has only a
getter

Avoid import of re-exported module.  Add new test suite for external
exports.

Author: wimpyprogrammer

src/index.spec.ts

@@ -0,0 +1,20 @@
+import * as indexLib from './index';
+import * as patternLib from './pattern';
+
+describe('index', () => {
+	it('exposes count()', () => {
+		expect(indexLib.count).toBe(patternLib.count);
+	});
+
+	it('exposes expand()', () => {
+		expect(indexLib.expand).toBe(patternLib.expand);
+	});
+
+	it('exposes expandN()', () => {
+		expect(indexLib.expandN).toBe(patternLib.expandN);
+	});
+
+	it('exposes expandAll()', () => {
+		expect(indexLib.expandAll).toBe(patternLib.expandAll);
+	});
+});

src/pattern.spec.ts

@@ -1,7 +1,7 @@
 import { when } from 'jest-when';
 import Expansion from './Expansion';
 import { fill } from './helpers/utils';
-import * as patternLib from './index';
+import * as patternLib from './pattern';
 import * as randomSort from './sorts/fisher-yates-random';
 import * as chooseRandom from './sorts/number-random';
 import * as chooseRandomWeighted from './sorts/weighted-random';