diff --git a/neurodsp/tests/test_filt_checks.py b/neurodsp/tests/test_filt_checks.py
index 144431fb..32b5776e 100644
--- a/neurodsp/tests/test_filt_checks.py
+++ b/neurodsp/tests/test_filt_checks.py
@@ -46,8 +46,18 @@ def test_check_filter_definition():
 def test_check_filter_properties():
 
     filter_coefs = design_fir_filter(FS, 'bandpass', (8, 12))
-    check_filter_properties(filter_coefs, 1, FS, 'bandpass', (8, 12))
-    assert True
+    
+    passes = check_filter_properties(filter_coefs, 1, FS, 'bandpass', (8, 12))
+    assert passes is True
+
+    filter_coefs = design_fir_filter(FS, 'bandstop', (8, 12))
+    passes = check_filter_properties(filter_coefs, 1, FS, 'bandpass', (8, 12))
+    assert passes is False
+
+    filter_coefs = design_fir_filter(FS, 'bandpass', (20, 21))
+    passes = check_filter_properties(filter_coefs, 1, FS, 'bandpass', (8, 12))
+    assert passes is False
+
 
 def test_check_filter_length():
 
diff --git a/neurodsp/tests/test_filt_fir.py b/neurodsp/tests/test_filt_fir.py
index e695457b..ddffdfd4 100644
--- a/neurodsp/tests/test_filt_fir.py
+++ b/neurodsp/tests/test_filt_fir.py
@@ -1,5 +1,6 @@
 """Tests for FIR filters."""
 
+from pytest import raises
 import numpy as np
 
 from neurodsp.tests.settings import FS
@@ -56,3 +57,7 @@ def test_compute_filter_length():
     expected_filt_len = int(np.ceil(fs * n_cycles / f_lo)) + 1
     filt_len = compute_filter_length(fs, 'bandpass', f_lo, f_hi, n_cycles=n_cycles, n_seconds=None)
     assert filt_len == expected_filt_len
+
+    with raises(ValueError):
+        filt_len = compute_filter_length(fs, 'bandpass', f_lo, f_hi)
+
diff --git a/neurodsp/tests/test_filt_iir.py b/neurodsp/tests/test_filt_iir.py
index bd37c149..4b209035 100644
--- a/neurodsp/tests/test_filt_iir.py
+++ b/neurodsp/tests/test_filt_iir.py
@@ -20,6 +20,9 @@ def test_filter_signal_iir_2d(tsig2d):
    assert out.shape == tsig2d.shape
    assert sum(~np.isnan(out[0, :])) > 0
 
+   out, sos = filter_signal_iir(tsig2d, FS, 'bandpass', (8, 12), 3, return_filter=True)
+   assert np.shape(sos)[1] == 6
+
 def test_apply_iir_filter(tsig):
 
     out = apply_iir_filter(tsig, np.array([1, 1, 1, 1, 1, 1]))
diff --git a/neurodsp/tests/test_filt_utils.py b/neurodsp/tests/test_filt_utils.py
index 01897d89..c839a75d 100644
--- a/neurodsp/tests/test_filt_utils.py
+++ b/neurodsp/tests/test_filt_utils.py
@@ -1,5 +1,6 @@
 """Tests for filter utilities."""
 
+from pytest import raises
 from neurodsp.tests.settings import FS
 
 from neurodsp.filt.utils import *
@@ -19,6 +20,9 @@ def test_compute_frequency_response():
     filter_coefs = design_fir_filter(FS, 'bandpass', (8, 12))
     f_db, db = compute_frequency_response(filter_coefs, 1, FS)
 
+    with raises(ValueError):
+        f_db, db = compute_frequency_response(filter_coefs, None, FS)
+
 def test_compute_pass_band():
 
     assert compute_pass_band(FS, 'bandpass', (4, 8)) == 4.