Code
pickerInput("test_id", "Test", choices = c("A", "B"))
Output
<div class="form-group shiny-input-container">
<label class="control-label" for="test_id">Test</label>
<select id="test_id" class="selectpicker form-control"><option value="A">A</option>
<option value="B">B</option></select>
</div>
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