diff --git a/tests/data/filter/filter_transmittance.csv b/tests/data/filter/filter_transmittance.csv
new file mode 100644
index 0000000..73fe3a6
--- /dev/null
+++ b/tests/data/filter/filter_transmittance.csv
@@ -0,0 +1,11 @@
+wavelength,spectral transmittance
+200,1
+201,1
+202,1
+203,1
+204,0.9
+205,0.9
+206,0.9
+207,0.8
+208,0.8
+209,0.7