diff --git a/create_spectrogram.py b/create_spectrogram.py
index eb00e0fc..6228044e 100644
--- a/create_spectrogram.py
+++ b/create_spectrogram.py
@@ -7,7 +7,7 @@
 from scipy.io import wavfile
 
 
-def create_spec_name(wav_name, output_dir):
+def create_spec_name(wav_name, output_dir=None):
     """Creates appropriate path to the spectrogram from input .wav file and output directory.
 
     Args:
@@ -18,7 +18,6 @@ def create_spec_name(wav_name, output_dir):
     """
     spec_name = path.splitext(path.basename(wav_name))[0]
     if output_dir is not None:
-        Path(output_dir).mkdir(parents=True, exist_ok=True)
         spec_name = f"{path.normpath(output_dir)}/{spec_name}"
     return f"{spec_name}.png"
 
@@ -46,7 +45,7 @@ def save_spectrogram(input_wav, plot_path=None, NFFT=256):
         `plot_path`: Path to the output spectrogram file. Default is `input_wav` with .png extension.
         `NFFT`: The number of data points used in each block for the FFT. A power 2 is most efficient.
     Returns:
-        None
+        Path to the spectrogram.
     """
     samplerate, data = wavfile.read(input_wav)
     noverlap = NFFT // 2 if NFFT <= 128 else 128
@@ -68,11 +67,14 @@ def save_spectrogram(input_wav, plot_path=None, NFFT=256):
 
     if plot_path is None:
         plot_path = input_wav.replace(".wav", ".png")
+    else:
+        Path(path.dirname(plot_path)).mkdir(parents=True, exist_ok=True)
     plt.savefig(plot_path)
 
     plt.cla()
     plt.close("all")
     logging.info("Finished " + input_wav)
+    return plot_path
 
 
 if __name__ == "__main__":
diff --git a/tests/ooi.wav b/tests/ooi.wav
new file mode 100755
index 00000000..698e3126
Binary files /dev/null and b/tests/ooi.wav differ
diff --git a/tests/orcasound.wav b/tests/orcasound.wav
new file mode 100755
index 00000000..0fe1adb5
Binary files /dev/null and b/tests/orcasound.wav differ
diff --git a/tests/test_spectrograms.py b/tests/test_spectrograms.py
new file mode 100644
index 00000000..5d7e4eb8
--- /dev/null
+++ b/tests/test_spectrograms.py
@@ -0,0 +1,44 @@
+"""Unit tests for various util functions relating to spectrogram creation"""
+import os.path
+
+import pytest
+
+from create_spectrogram import create_spec_name, save_spectrogram
+
+
+@pytest.mark.parametrize(
+    "wav_name, output_dir, expected",
+    [
+        ("2021-01-01T00-00-00-000.wav", None, "2021-01-01T00-00-00-000.png"),
+        (
+            "2021-01-01T00-00-00-000.wav",
+            "spectrograms",
+            "spectrograms/2021-01-01T00-00-00-000.png",
+        ),
+        (
+            "2021-01-01T00-00-00-000.wav",
+            "long/path/to/output",
+            "long/path/to/output/2021-01-01T00-00-00-000.png",
+        ),
+        (
+            "2021-01-01T00-00-00-000.wav",
+            "end/slash/",
+            "end/slash/2021-01-01T00-00-00-000.png",
+        ),
+    ],
+)
+def test_create_spec_name(wav_name, output_dir, expected):
+    assert create_spec_name(wav_name, output_dir) == expected
+
+
+@pytest.mark.parametrize(
+    "wav_name, plot_path",
+    [
+        ("tests/ooi.wav", None),
+        ("tests/ooi.wav", "tests/path/to/output/ooi.png"),
+        ("tests/orcasound.wav", "tests/path/to/output/orcasound.png"),
+    ],
+)
+def test_save_spectrogram(wav_name, plot_path):
+    spec_path = save_spectrogram(wav_name, plot_path)
+    assert os.path.isfile(spec_path)