test(loaders): Add test for load_sound_speed (#166)

* test(loaders): Add test for load_sound_speed
* Improve unittest coverage for loaders.py `load_sound_speed()`
* Issue #124 #124

* * Verify data types of columns in svdf dataframe

tests/test_loaders.py

@@ -1,10 +1,22 @@
+from typing import Any, Dict
+
 import pytest
+from numpy import float64
+from pandas import DataFrame
 
 from gnatss.configs.main import Configuration
-from gnatss.loaders import load_configuration
+from gnatss.constants import SP_DEPTH, SP_SOUND_SPEED
+from gnatss.loaders import load_configuration, load_sound_speed
+from gnatss.main import gather_files
 from tests import TEST_DATA_FOLDER
 
 
+@pytest.fixture
+def all_files_dict() -> Dict[str, Any]:
+    config = load_configuration(TEST_DATA_FOLDER / "config.yaml")
+    return gather_files(config)
+
+
 @pytest.mark.parametrize(
     "config_yaml_path",
     [(None), (TEST_DATA_FOLDER / "invalid_config.yaml")],
@@ -22,3 +34,10 @@ def test_load_configuration_invalid_path(config_yaml_path):
 def test_load_configuration_valid_path(config_yaml_path):
     config = load_configuration(config_yaml_path)
     assert isinstance(config, Configuration)
+
+
+def test_load_sound_speed(all_files_dict):
+    svdf = load_sound_speed(all_files_dict["sound_speed"])
+    assert isinstance(svdf, DataFrame)
+    assert {SP_DEPTH, SP_SOUND_SPEED} == set(svdf.columns.values.tolist())
+    assert svdf.dtypes[SP_DEPTH] == float64 and svdf.dtypes[SP_SOUND_SPEED] == float64