Add tests for .eachIndex() method

methods/eachIndex/tests.js

@@ -0,0 +1,27 @@
+import test from 'ava';
+import eachIndex from '.';
+
+test('passes the index of each item to the callback', t => {
+    const results = [];
+    const callback = x => results.push(x);
+
+    eachIndex([1, 2, 3, 4, 5], callback);
+
+    t.deepEqual(results, [0, 1, 2, 3, 4]);
+});
+
+test('returns the given array', t => {
+    const results = [];
+    const callback = x => results.push(x);
+
+    const array = [1, 2, 3, 4, 5];
+
+    t.is(array, eachIndex(array, callback));
+});
+
+test('throws TypeError if callback is not provided', t => {
+    const error = t.throws(() => {
+        eachIndex([1, 2, 3, 4, 5]);
+    }, TypeError);
+    t.is(error.message, 'Parameter "callback" must be a function.');
+});