2.6: Buttons Uncheckable Radio example
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**Primary Actor**: User

**Scope**: Ngx-bootstrap DEMO / BS version 3&4

**Goal**: Show user uncheckable radio buttons example

Main success scenario:
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1. User opens Buttons demo page
2. User clicks on Radio without explicit group sub-menu
3. User sees button-group, contains 3 clickable buttons named "Left", "Middle" and "Right", with the custom checkbox value field under it
4. By default, 1st button is inactive, 2d - active and 3d - inactive, and the text: "Middle" displayed in the custom checkbox value field
5. User is able to click on each button
6. When user clicks on the inactive button, it becomes active, other buttons become inactive, and the text with that button name is displayed in the custom checkbox value field
7. When user clicks on this button a second time, it becomes inactive, and the text: "null" shown in the custom checkbox value field
8. When user press on the arrow key to switch on the next button, the next button become active and this button name shown in the custom checkbox value field
10. When user presses the space key after that, the text: "null" shown in the custom checkbox value field

Variations:
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2*. User scrolls to Uncheckable Radio sub-menu
9*. When user click on the Middle button after that, the text: "null" shown in the custom checkbox value field.