source: frontend/node_modules/object.groupby/test/tests.js

'use strict';

var inspect = require('object-inspect');
var forEach = require('for-each');
var v = require('es-value-fixtures');

module.exports = function (groupBy, t) {
        t.test('callback function', function (st) {
                forEach(v.nonFunctions, function (nonFunction) {
                        st['throws'](
                                function () { groupBy([], nonFunction); },
                                TypeError,
                                inspect(nonFunction) + ' is not a function'
                        );
                });

                st.end();
        });

        t.test('grouping', function (st) {
                st.deepEqual(
                        groupBy([], function () { return 'a'; }),
                        { __proto__: null },
                        'an empty array produces an empty object'
                );

                var arr = [0, -0, 1, 2, 3, 4, 5, NaN, Infinity, -Infinity];
                var parity = function (x) {
                        if (x !== x) {
                                return void undefined;
                        }
                        if (!isFinite(x)) {
                                return '∞';
                        }
                        return x % 2 === 0 ? 'even' : 'odd';
                };
                var grouped = {
                        __proto__: null,
                        even: [0, -0, 2, 4],
                        odd: [1, 3, 5],
                        undefined: [NaN],
                        '∞': [Infinity, -Infinity]
                };
                st.deepEqual(
                        groupBy(arr, parity),
                        grouped,
                        inspect(arr) + ' group by parity groups to ' + inspect(grouped)
                );

                st.deepEqual(
                        groupBy(arr, function (x, i) {
                                st.equal(this, undefined, 'receiver is as expected'); // eslint-disable-line no-invalid-this
                                st.equal(x, arr[i], 'second argument ' + i + ' is ' + inspect(arr[i]));
                                return 42;
                        }),
                        { __proto__: null, 42: arr },
                        'thisArg and callback arguments are as expected'
                );

                st.end();
        });
};