def METHOD_NAME(self):
    layers = [
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "a"}, {}))
        ),
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "b"}, {}))
        ),
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "c"}, {}))
        ),
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "d"}, {}))
        ),
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "e"}, {}))
        ),
        WMSSource(
            WMSClient(create_request({"url": "http://foo/", "layers": "f"}, {}))
        ),
    ]
    layers[0].supported_srs = ["EPSG:4326"]
    layers[1].supported_srs = ["EPSG:4326"]
    layers[2].supported_formats = ["image/png"]
    layers[3].supported_formats = ["image/png"]
    combined = combined_layers(layers, self.q)
    assert len(combined) == 3
    assert combined[0].client.request_template.params.layers == ["a", "b"]
    assert combined[1].client.request_template.params.layers == ["c", "d"]
    assert combined[2].client.request_template.params.layers == ["e", "f"]