Fix API Tile Metadata JSON response (#1934)

* Add test for Tile metadata

* Serialize tile metadata response to json

* Update test_tiles.py

pygeoapi/api/tiles.py

@@ -262,7 +262,6 @@ def get_collection_tiles_data(
             err.ogc_exception_code, err.message)
 
 
-# TODO: no test for this function?
 def get_collection_tiles_metadata(
     api: API, request: APIRequest,
         dataset=None, matrix_id=None) -> Tuple[dict, int, str]:
@@ -328,9 +327,10 @@ def get_collection_tiles_metadata(
                                      'collections/tiles/metadata.html',
                                      tiles_metadata, request.locale)
 
-        return headers, HTTPStatus.OK, content
     else:
-        return headers, HTTPStatus.OK, tiles_metadata
+        content = to_json(tiles_metadata, api.pretty_print)
+
+    return headers, HTTPStatus.OK, content
 
 
 def tilematrixsets(api: API,

tests/api/test_tiles.py

@@ -34,10 +34,12 @@
 
 import json
 from http import HTTPStatus
+import pytest
 
 from pygeoapi.api import FORMAT_TYPES, F_HTML
 from pygeoapi.api.tiles import (
-    get_collection_tiles, tilematrixset, tilematrixsets,
+    get_collection_tiles, tilematrixset,
+    tilematrixsets, get_collection_tiles_metadata
 )
 from pygeoapi.models.provider.base import TileMatrixSetEnum
 
@@ -83,6 +85,23 @@ def test_tilematrixsets(config, api_):
     assert rsp_headers['Content-Language'] == 'en-US'
 
 
+@pytest.mark.parametrize('file_format', ['html', 'json', 'tilejson'])
+def test_get_collection_tiles_metadata_bad_request(api_, file_format):
+    req = mock_api_request({'f': file_format})
+    _, code, _ = get_collection_tiles_metadata(
+        api_, req, 'obs', 'WorldCRS84Quad')
+    assert code == HTTPStatus.BAD_REQUEST
+
+
+@pytest.mark.parametrize('file_format', ['json', 'tilejson'])
+def test_get_collection_tiles_metadata_formats(api_, file_format):
+    req = mock_api_request({'f': file_format})
+    _, code, response = get_collection_tiles_metadata(
+        api_, req, 'naturalearth/lakes', matrix_id='WebMercatorQuad')
+    assert code == HTTPStatus.OK
+    assert json.loads(response)
+
+
 def test_tilematrixset(config, api_):
     req = mock_api_request()