diff --git a/tests/detectors/conftest.py b/tests/detectors/conftest.py
new file mode 100644
index 0000000..657d789
--- /dev/null
+++ b/tests/detectors/conftest.py
@@ -0,0 +1,17 @@
+import pytest
+from statsmodels.datasets import co2
+
+
+@pytest.fixture(scope="module")
+def co2_daily():
+    return co2.load().data.resample("D").mean().ffill()
+
+
+@pytest.fixture(scope="module")
+def co2_weekly():
+    return co2.load().data.resample("W").mean().ffill()
+
+
+@pytest.fixture(scope="module")
+def co2_monthly():
+    return co2.load().data.resample("ME").mean().ffill()
diff --git a/tests/detectors/test_acf.py b/tests/detectors/test_acf.py
index b5eafdb..0d58b21 100644
--- a/tests/detectors/test_acf.py
+++ b/tests/detectors/test_acf.py
@@ -1,119 +1,117 @@
-from statsmodels.datasets import co2
-
 from pyriodicity import ACFPeriodicityDetector
 
 
-def test_co2_daily_acf_default():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_acf_default(co2_daily):
+    data = co2_daily
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit()
     assert len(periods) > 0
 
 
-def test_co2_weekly_acf_default():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_acf_default(co2_weekly):
+    data = co2_weekly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit()
     assert len(periods) > 0
 
 
-def test_co2_monthly_acf_default():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_acf_default(co2_monthly):
+    data = co2_monthly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit()
     assert len(periods) > 0
 
 
-def test_co2_daily_acf_max_period_count_one():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_acf_max_period_count_one(co2_daily):
+    data = co2_daily
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 364 in periods
 
 
-def test_co2_weekly_acf_max_period_count_one():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_acf_max_period_count_one(co2_weekly):
+    data = co2_weekly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_acf_max_period_count_one():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_acf_max_period_count_one(co2_monthly):
+    data = co2_monthly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_acf_max_period_count_one_correlation_func_spearman():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_acf_max_period_count_one_correlation_func_spearman(co2_daily):
+    data = co2_daily
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="spearman")
     assert len(periods) == 1
     assert 364 in periods
 
 
-def test_co2_weekly_acf_max_period_count_one_correlation_func_spearman():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_acf_max_period_count_one_correlation_func_spearman(co2_weekly):
+    data = co2_weekly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="spearman")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_acf_max_period_count_one_correlation_func_spearman():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_acf_max_period_count_one_correlation_func_spearman(co2_monthly):
+    data = co2_monthly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="spearman")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_acf_max_period_count_one_correlation_func_kendall():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_acf_max_period_count_one_correlation_func_kendall(co2_daily):
+    data = co2_daily
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="kendall")
     assert len(periods) == 1
     assert 364 in periods
 
 
-def test_co2_weekly_acf_max_period_count_one_correlation_func_kendall():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_acf_max_period_count_one_correlation_func_kendall(co2_weekly):
+    data = co2_weekly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="kendall")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_acf_max_period_count_one_correlation_func_kendall():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_acf_max_period_count_one_correlation_func_kendall(co2_monthly):
+    data = co2_monthly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, correlation_func="kendall")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_acf_max_period_count_one_window_func_blackman():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_acf_max_period_count_one_window_func_blackman(co2_daily):
+    data = co2_daily
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
     assert 364 in periods
 
 
-def test_co2_weekly_acf_max_period_count_one_window_func_blackman():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_acf_max_period_count_one_window_func_blackman(co2_weekly):
+    data = co2_weekly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_acf_max_period_count_one_window_func_blackman():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_acf_max_period_count_one_window_func_blackman(co2_monthly):
+    data = co2_monthly
     acf_detector = ACFPeriodicityDetector(data)
     periods = acf_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
diff --git a/tests/detectors/test_autoperiod.py b/tests/detectors/test_autoperiod.py
index 8bfb1bb..529e1d5 100644
--- a/tests/detectors/test_autoperiod.py
+++ b/tests/detectors/test_autoperiod.py
@@ -1,92 +1,90 @@
-from statsmodels.datasets import co2
-
 from pyriodicity import Autoperiod
 
 
-def test_co2_daily_autoperiod_default():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_autoperiod_default(co2_daily):
+    data = co2_daily
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit()
     assert len(periods) > 0
     assert 364 in periods
 
 
-def test_co2_weekly_autoperiod_default():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_autoperiod_default(co2_weekly):
+    data = co2_weekly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit()
     assert len(periods) > 0
     assert 52 in periods
 
 
-def test_co2_monthly_autoperiod_default():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_autoperiod_default(co2_monthly):
+    data = co2_monthly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit()
     assert len(periods) > 0
     assert 12 in periods
 
 
-def test_co2_daily_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_autoperiod_detrend_func_none(co2_daily):
+    data = co2_daily
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_weekly_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_autoperiod_detrend_func_none(co2_weekly):
+    data = co2_weekly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_monthly_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_autoperiod_detrend_func_none(co2_monthly):
+    data = co2_monthly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_daily_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_autoperiod_detrend_func_constant(co2_daily):
+    data = co2_daily
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_weekly_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_autoperiod_detrend_func_constant(co2_weekly):
+    data = co2_weekly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_monthly_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_autoperiod_detrend_func_constant(co2_monthly):
+    data = co2_monthly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_daily_autoperiod_detrend_func_constant_window_func_blackman():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_autoperiod_detrend_func_constant_window_func_blackman(co2_daily):
+    data = co2_daily
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant", window_func="blackman")
     assert len(periods) > 0
     assert 364 in periods
 
 
-def test_co2_weekly_autoperiod_detrend_func_constant_window_func_blackman():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_autoperiod_detrend_func_constant_window_func_blackman(co2_weekly):
+    data = co2_weekly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant", window_func="blackman")
     assert len(periods) > 0
     assert 52 in periods
 
 
-def test_co2_monthly_autoperiod_detrend_func_constant_window_func_blackman():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_autoperiod_detrend_func_constant_window_func_blackman(co2_monthly):
+    data = co2_monthly
     autoperiod = Autoperiod(data)
     periods = autoperiod.fit(detrend_func="constant", window_func="blackman")
     assert len(periods) > 0
diff --git a/tests/detectors/test_cfd_autoperiod.py b/tests/detectors/test_cfd_autoperiod.py
index 744e508..7d8f097 100644
--- a/tests/detectors/test_cfd_autoperiod.py
+++ b/tests/detectors/test_cfd_autoperiod.py
@@ -1,93 +1,91 @@
-from statsmodels.datasets import co2
-
 from pyriodicity import CFDAutoperiod
 
 
-def test_co2_daily_cfd_autoperiod_default():
-    data = co2.load().data.resample("D").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit()
+def test_co2_daily_cfd_autoperiod_default(co2_daily):
+    data = co2_daily
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit()
     assert len(periods) > 0
     assert 364 in periods
 
 
-def test_co2_weekly_cfd_autoperiod_default():
-    data = co2.load().data.resample("W").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit()
+def test_co2_weekly_cfd_autoperiod_default(co2_weekly):
+    data = co2_weekly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit()
     assert len(periods) > 0
     assert 52 in periods
 
 
-def test_co2_monthly_cfd_autoperiod_default():
-    data = co2.load().data.resample("ME").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit()
+def test_co2_monthly_cfd_autoperiod_default(co2_monthly):
+    data = co2_monthly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit()
     assert len(periods) > 0
     assert 12 in periods
 
 
-def test_co2_daily_cfd_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("D").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func=None)
+def test_co2_daily_cfd_autoperiod_detrend_func_none(co2_daily):
+    data = co2_daily
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_weekly_cfd_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("W").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func=None)
+def test_co2_weekly_cfd_autoperiod_detrend_func_none(co2_weekly):
+    data = co2_weekly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_monthly_cfd_autoperiod_detrend_func_none():
-    data = co2.load().data.resample("ME").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func=None)
+def test_co2_monthly_cfd_autoperiod_detrend_func_none(co2_monthly):
+    data = co2_monthly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func=None)
     assert len(periods) == 0
 
 
-def test_co2_daily_cfd_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("D").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func="constant")
+def test_co2_daily_cfd_autoperiod_detrend_func_constant(co2_daily):
+    data = co2_daily
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_weekly_cfd_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("W").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func="constant")
+def test_co2_weekly_cfd_autoperiod_detrend_func_constant(co2_weekly):
+    data = co2_weekly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_monthly_cfd_autoperiod_detrend_func_constant():
-    data = co2.load().data.resample("ME").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(detrend_func="constant")
+def test_co2_monthly_cfd_autoperiod_detrend_func_constant(co2_monthly):
+    data = co2_monthly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(detrend_func="constant")
     assert len(periods) == 0
 
 
-def test_co2_daily_cfd_autoperiod_window_func_blackman():
-    data = co2.load().data.resample("D").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(window_func="blackman")
+def test_co2_daily_cfd_autoperiod_window_func_blackman(co2_daily):
+    data = co2_daily
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(window_func="blackman")
     assert len(periods) > 0
     assert 364 in periods
 
 
-def test_co2_weekly_cfd_autoperiod_window_func_blackman():
-    data = co2.load().data.resample("W").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(window_func="blackman")
+def test_co2_weekly_cfd_autoperiod_window_func_blackman(co2_weekly):
+    data = co2_weekly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(window_func="blackman")
     assert len(periods) > 0
     assert 52 in periods
 
 
-def test_co2_monthly_cfd_autoperiod_window_func_blackman():
-    data = co2.load().data.resample("ME").mean().ffill()
-    autoperiod = CFDAutoperiod(data)
-    periods = autoperiod.fit(window_func="blackman")
+def test_co2_monthly_cfd_autoperiod_window_func_blackman(co2_monthly):
+    data = co2_monthly
+    cfd_autoperiod = CFDAutoperiod(data)
+    periods = cfd_autoperiod.fit(window_func="blackman")
     assert len(periods) > 0
     assert 12 in periods
diff --git a/tests/detectors/test_fft.py b/tests/detectors/test_fft.py
index 3bf6208..6ee847e 100644
--- a/tests/detectors/test_fft.py
+++ b/tests/detectors/test_fft.py
@@ -1,232 +1,230 @@
-from statsmodels.datasets import co2
-
 from pyriodicity import FFTPeriodicityDetector
 
 
-def test_co2_monthly_fft_find_all_periods():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_all_periods(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit()
     assert len(periods) > 0
 
 
-def test_co2_monthly_fft_find_first_two_periods():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_first_two_periods(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=2)
     assert len(periods) == 2
 
 
-def test_co2_daily_fft_find_strongest_period():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1)
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_barthann():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_barthann(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="barthann")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_barthann():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_barthann(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="barthann")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_barthann():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_barthann(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="barthann")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_bartlett():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_bartlett(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="bartlett")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_bartlett():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_bartlett(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="bartlett")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_bartlett():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_bartlett(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="bartlett")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_blackman():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_blackman(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_blackman():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_blackman(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_blackman():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_blackman(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackman")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_blackmanharris():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_blackmanharris(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackmanharris")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_blackmanharris():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_blackmanharris(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackmanharris")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_blackmanharris():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_blackmanharris(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="blackmanharris")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_boxcar():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_boxcar(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="boxcar")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_boxcar():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_boxcar(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="boxcar")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_boxcar():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_boxcar(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="boxcar")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_hamming():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_hamming(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hamming")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_hamming():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_hamming(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hamming")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_hamming():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_hamming(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hamming")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_hann():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_hann(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hann")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_hann():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_hann(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hann")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_hann():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_hann(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="hann")
     assert len(periods) == 1
     assert 12 in periods
 
 
-def test_co2_daily_fft_find_strongest_period_window_func_tukey():
-    data = co2.load().data.resample("D").mean().ffill()
+def test_co2_daily_fft_find_strongest_period_window_func_tukey(co2_daily):
+    data = co2_daily
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="tukey")
     assert len(periods) == 1
     assert 363 in periods
 
 
-def test_co2_weekly_fft_find_strongest_period_window_func_tukey():
-    data = co2.load().data.resample("W").mean().ffill()
+def test_co2_weekly_fft_find_strongest_period_window_func_tukey(co2_weekly):
+    data = co2_weekly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="tukey")
     assert len(periods) == 1
     assert 52 in periods
 
 
-def test_co2_monthly_fft_find_strongest_period_window_func_tukey():
-    data = co2.load().data.resample("ME").mean().ffill()
+def test_co2_monthly_fft_find_strongest_period_window_func_tukey(co2_monthly):
+    data = co2_monthly
     fft_detector = FFTPeriodicityDetector(data)
     periods = fft_detector.fit(max_period_count=1, window_func="tukey")
     assert len(periods) == 1