ran npm run tdd

test/sumBy/sumBy.js

@@ -0,0 +1,2 @@
+module.exports = sumBy = (arr, fn) =>
+arr.map(typeof fn === 'function' ? fn : val => val[fn]).reduce((acc, val) => acc + val, 0);

test/sumBy/sumBy.test.js

@@ -0,0 +1,13 @@
+const test = require('tape');
+const sumBy = require('./sumBy.js');
+
+test('Testing sumBy', (t) => {
+	//For more information on all the methods supported by tape
+	//Please go to https://github.com/substack/tape
+	t.true(typeof sumBy === 'function', 'sumBy is a Function');
+	//t.deepEqual(sumBy(args..), 'Expected');
+	//t.equal(sumBy(args..), 'Expected');
+	//t.false(sumBy(args..), 'Expected');
+	//t.throws(sumBy(args..), 'Expected');
+	t.end();
+});