Updated test file paths for consistency

Previously, test file paths were specified relative to the working
directory (e.g., `test_file_path = './<path>/'`). This approach led to
test failures, especially when using Poetry to run tests from the root
directory with the command `poetry run pytest`. The paths have now been
adjusted to ensure consistent behavior across directories, resolving the
issue.

tests/test_new_objects.py

@@ -2,14 +2,16 @@
 import pyhydrophone as pyhy
 import unittest
 
+TEST_DATA_DIR = pathlib.Path(__file__).parent / "test_data"
+
 
 class TestHydrophones(unittest.TestCase):
     def test_st(self):
         # Hydrophone Setup
         model = 1
         name = 'SoundTrap'
         serial_number = 67416073
-        calibration_file = pathlib.Path("./test_data/soundtrap/calibration_data.xlsx")
+        calibration_file = TEST_DATA_DIR / "soundtrap" / "calibration_data.xlsx"
 
         st = pyhy.SoundTrap(name, model, serial_number, calibration_file=calibration_file, val='sensitivity',
                             freq_col_id=1, val_col_id=29, start_data_id=6)
@@ -67,7 +69,7 @@ def test_rtsys(self):
         rtsys_preamp_gain = 0
         rtsys_Vpp = 2.0
         serial_number = 3
-        calibration_file = pathlib.Path("./test_data/rtsys/SN130.csv")
+        calibration_file = TEST_DATA_DIR / "rtsys" / "SN130.csv"
         rtsys = pyhy.RTSys(name=rtsys_name, model=rtsys_model, serial_number=serial_number,
                            sensitivity=rtsys_sensitivity,
                            preamp_gain=rtsys_preamp_gain, Vpp=rtsys_Vpp, mode='lowpower', channel='A',

tests/test_rtsys.py

@@ -3,9 +3,10 @@
 import unittest
 import numpy as np
 
+CURRENT_DIR = pathlib.Path(__file__).parent
 
-test_folder = pathlib.Path("./test_data/rtsys/")
-test_file = pathlib.Path("./test_data/rtsys/channelA_2021-10-11_13-11-09.wav")
+test_folder = CURRENT_DIR / "test_data" / "rtsys"
+test_file = test_folder / "channelA_2021-10-11_13-11-09.wav"
 
 rtsys_name = 'RTSys'
 rtsys_model = 'RESEA320'
@@ -14,7 +15,7 @@
 rtsys_preamp = 0
 rtsys_vpp = 5
 mode = 'lowpower'
-calibration_file = pathlib.Path("./test_data/rtsys/SN130.csv")
+calibration_file = test_folder / "SN130.csv"
 rtsys = pyhy.RTSys(name=rtsys_name, model=rtsys_model, serial_number=rtsys_serial_number, sensitivity=rtsys_sens,
                    preamp_gain=rtsys_preamp, Vpp=rtsys_vpp, mode=mode, calibration_file=calibration_file)