Updated the test system

test/toSnakeCase.test.js

@@ -0,0 +1,48 @@
+const expect = require('expect');
+const {toSnakeCase} = require('./_30s.js');
+
+test('toSnakeCase is a Function', () => {
+  expect(toSnakeCase).toBeInstanceOf(Function);
+});
+test("toSnakeCase('camelCase') returns camel_case", () => {
+  expect(toSnakeCase('camelCase')).toBe('camel_case');
+});
+test("toSnakeCase('some text') returns some_text", () => {
+  expect(toSnakeCase('some text')).toBe('some_text');
+});
+test("toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens') returns some_mixed_string_with_spaces_underscores_and_hyphens", () => {
+  expect(toSnakeCase('some-mixed_string With spaces_underscores-and-hyphens')).toBe(
+    'some_mixed_string_with_spaces_underscores_and_hyphens'
+  );
+});
+test("toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML') returns i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html", () => {
+  expect(
+    toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML')
+  ).toBe(
+    'i_am_listening_to_fm_while_loading_different_url_on_my_browser_and_also_editing_some_xml_and_html'
+  );
+});
+test('toSnakeCase() returns undefined', () => {
+  expect(toSnakeCase()).toBe(undefined);
+});
+test('toSnakeCase([]) throws an error', () => {
+  expect(() => {
+    toSnakeCase([]);
+  }).toThrow();
+});
+test('toSnakeCase({}) throws an error', () => {
+  expect(() => {
+    toSnakeCase({});
+  }).toThrow();
+});
+test('toSnakeCase(123) throws an error', () => {
+  expect(() => {
+    toSnakeCase(123);
+  }).toThrow();
+});
+let start = new Date().getTime();
+toSnakeCase('IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML');
+let end = new Date().getTime();
+test('toSnakeCase(IAmListeningToFMWhileLoadingDifferentURLOnMyBrowserAndAlsoEditingSomeXMLAndHTML) takes less than 2s to run', () => {
+  expect(end - start < 2000).toBeTruthy();
+});