Auto merge of #87 - vikram7:vr-add-underscore, r=poteto

Add string underscore helper

This PR adds the `underscore` helper per issue https://github.com/DockYard/ember-composable-helpers/issues/69

README.md

@@ -66,6 +66,7 @@ For action helpers, this will mean better currying semantics:
 * [String](#string-helpers)
   + [`capitalize`](#capitalize)
   + [`dasherize`](#dasherize)
+  + [`underscore`](#underscore)
   + [`w`](#w)
 * [Array](#array-helpers)
   + [`map-by`](#map-by)
@@ -146,6 +147,16 @@ Capitalizes a string using `Ember.String.dasherize`.
 
 **[⬆️ back to top](#available-helpers)**
 
+#### `underscore`
+Capitalizes a string using `Ember.String.underscore`.
+
+```hbs
+{{underscore "whatsThat"}}
+{{underscore phrase}}
+```
+
+**[⬆️ back to top](#available-helpers)**
+
 #### `w`
 Splits a string on whitespace and/or turns multiple words into an array
 

addon/helpers/underscore.js

@@ -0,0 +1,12 @@
+import Ember from 'ember';
+const {
+  Helper: { helper },
+  String: { underscore: _underscore }
+} = Ember;
+
+export function underscore([string]) {
+  string = string || '';
+  return _underscore(string);
+}
+
+export default helper(underscore);

addon/index.js

@@ -18,5 +18,6 @@ export { default as RepeatHelper } from './helpers/repeat';
 export { default as SortByHelper } from './helpers/sort-by';
 export { default as TakeHelper } from './helpers/take';
 export { default as ToggleHelper } from './helpers/toggle';
+export { default as UnderscoreHelper } from './helpers/underscore';
 export { default as UnionHelper } from './helpers/union';
 export { default as WHelper } from './helpers/w';

app/helpers/underscore.js

@@ -0,0 +1 @@
+export { default, underscore } from 'ember-composable-helpers/helpers/underscore';

tests/integration/helpers/underscore-test.js

@@ -0,0 +1,46 @@
+import { moduleForComponent, test } from 'ember-qunit';
+import hbs from 'htmlbars-inline-precompile';
+
+moduleForComponent('underscore', 'Integration | Helper | {{underscore}}', {
+  integration: true
+});
+
+test('It converts camelCase correctly', function(assert) {
+  this.render(hbs`{{underscore "andAnother"}}`);
+
+  let expected = 'and_another';
+
+  assert.equal(this.$().text().trim(), expected, 'converts camelCase to underscored');
+});
+
+test('It converts dashes to underscores', function(assert) {
+  this.render(hbs`{{underscore "harry-potter"}}`);
+
+  let expected = 'harry_potter';
+
+  assert.equal(this.$().text().trim(), expected, 'converts dashes to underscores');
+});
+
+test('It converts spaces to underscores', function(assert) {
+  this.render(hbs`{{underscore "age is foolish and forgetful when it underestimates youth"}}`);
+
+  let expected = 'age_is_foolish_and_forgetful_when_it_underestimates_youth';
+
+  assert.equal(this.$().text().trim(), expected, 'converts spaces to underscores');
+});
+
+test('It correctly handles empty string input', function(assert) {
+  this.render(hbs`{{underscore ""}}`);
+
+  let expected = '';
+
+  assert.equal(this.$().text().trim(), expected, 'renders empty string if input is empty string');
+});
+
+test('It correctly handles undefined input', function(assert) {
+  this.render(hbs`{{underscore undefined}}`);
+
+  let expected = '';
+
+  assert.equal(this.$().text().trim(), expected, 'renders empty string if undefined input');
+});