code: @Nonnull
    public MockHttpServletRequest setParameter (@Nonnull final String sName, @Nullable final String sValue)
    {
      m_aParameters.remove (sName);
      m_aParameters.add (sName, sValue);
      return this;
    }
docs: Set a single value for the specified HTTP parameter.
  <p>
  If there are already one or more values registered for the given parameter
  name, they will be replaced.
  
  @param sName
  Parameter name
  @param sValue
  Parameter value
  @return this