diff --git a/tja2fumen/tja2fumen.py b/tja2fumen/tja2fumen.py
index ceacd99..5d8076f 100644
--- a/tja2fumen/tja2fumen.py
+++ b/tja2fumen/tja2fumen.py
@@ -6,31 +6,39 @@ from utils import checkMismatchedBytes
 tja2fumen_version = "v0.1"
 
 
-if __name__ == "__main__":
-    # arguments = parser.parse_args()
-    arguments = {
-        "input_fumen": "test-data/ia6cho_m.bin",  # NB: Contains only oni chart
-        "input_tja": "test-data/Rokuchounen to Ichiya Monogatari.tja",  # NB: Contains 5 charts
-    }
-    # Parse fumen
-    inputFile = open(arguments["input_fumen"], "rb")
-    parsedSongFumen = readFumen(inputFile)
+def main(fnameFumen=None, fnameTJA=None, validate=False):
+    if fnameFumen:
+        # Parse fumen
+        inputFile = open(fnameFumen, "rb")
+        parsedSongFumen = readFumen(inputFile)
 
-    # Steps to validate the `writeFumen` function to make sure it reproduces correct output
-    validate = False
-    if validate:
-        outputName = inputFile.name.split('.')[0] + "_rebuilt.bin"
+        # Steps to validate the `writeFumen` function to make sure it reproduces correct output
+        if validate:
+            outputName = inputFile.name.split('.')[0] + "_rebuilt.bin"
+            outputFile = open(outputName, "wb")
+            writeFumen(outputFile, parsedSongFumen)
+            # Read output file back in to validate that the rewritten song is a perfect match
+            print(False if checkMismatchedBytes(inputFile.name, outputFile.name) else True)
+    else:
+        parsedSongFumen = None
+
+    if fnameTJA:
+        # Parse tja
+        inputFile = open(fnameTJA, "r", encoding="utf-8-sig")
+        parsedSongsTJA = parseTJA(inputFile)
+
+        # Try converting the Oni TJA chart to match the Oni fumen
+        convertedTJA = convertTJAToFumen(parsedSongFumen, parsedSongsTJA['Oni'])
+        outputName = inputFile.name.split('.')[0] + ".bin"
         outputFile = open(outputName, "wb")
-        writeFumen(outputFile, parsedSongFumen)
-        # Read output file back in to validate that the rewritten song is a perfect match
-        print(False if checkMismatchedBytes(inputFile.name, outputFile.name) else True)
+        writeFumen(outputFile, convertedTJA)
+    else:
+        convertedTJA = None
 
-    # Parse tja
-    inputFile = open(arguments["input_tja"], "r", encoding="utf-8-sig")
-    parsedSongsTJA = parseTJA(inputFile)
+    return parsedSongFumen, convertedTJA
 
-    # Try converting the Oni TJA chart to match the Oni fumen
-    convertedTJA = convertTJAToFumen(parsedSongFumen, parsedSongsTJA['Oni'])
-    outputName = inputFile.name.split('.')[0] + ".bin"
-    outputFile = open(outputName, "wb")
-    writeFumen(outputFile, convertedTJA)
+
+if __name__ == "__main__":
+    fnameFumen = "test-data/ia6cho_m.bin"  # NB: Contains only oni chart
+    fnameTJA = "test-data/Rokuchounen to Ichiya Monogatari.tja"  # NB: Contains 5 charts
+    fumen, tja = main(fnameFumen, fnameTJA)