code: @Test public void testIsModified(){
    HttpCacheToolkit httpCacheToolkit=new HttpCacheToolkitImpl(ninjaProperties);
    when(context.getHeader(HttpHeaderConstants.IF_NONE_MATCH)).thenReturn("etag_xyz");
    assertFalse(httpCacheToolkit.isModified(Optional.of("etag_xyz"),Optional.of(0L),context));
    assertTrue(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(0L),context));
    when(context.getHeader(HttpHeaderConstants.IF_NONE_MATCH)).thenReturn(null);
    when(context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE)).thenReturn(null);
    assertTrue(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(0L),context));
    when(context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE)).thenReturn("Thu, 01 Jan 1970 00:00:00 GMT");
    assertTrue(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(1000L),context));
    when(context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE)).thenReturn("Thu, 01 Jan 1970 00:00:00 GMT");
    assertFalse(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(0L),context));
    when(context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE)).thenReturn("Thu, 01 Jan 1971 00:00:00 GMT");
    assertFalse(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(0L),context));
    when(context.getHeader(HttpHeaderConstants.IF_MODIFIED_SINCE)).thenReturn("STRANGE_TIMESTAMP");
    assertTrue(httpCacheToolkit.isModified(Optional.of("etag_xyz_modified"),Optional.of(0L),context));
  }
  