<div class="test">
  <div class="row">
    <div class="col-xs-3">
      <label>
        <span>Test label</span>
        <input type="text" />
      </label>
    </div>
    <div class="col-xs-3">
      <label>
        <span>Test label</span>
        <input type="text" />
      </label>
    </div>
    <div class="col-xs-3">
      <label>
        <span>Test label</span>
        <input type="text" />
      </label>
    </div>
    <div class="col-xs-3">
      <label>
        <span>Test label</span>
        <input type="text" />
      </label>
    </div>
  </div>
</div>

label {
  padding-left: 5px;
  display: flex;
  width: 100%;
}
input {
  margin-left: 5px;
  flex: 1;
}