testpyisomd5sum.py: Use a consistent iso size

The test script used to use the directory content for the test.
Depending on the circumstances this could vary in size and fail because
isomd5sum does not work on small isos.

This uses part of the reverted test to make a 500k file/iso to use for
testing. Smaller or larger sizes may be set by passing the size in K on
the cmdline.

testpyisomd5sum.py

@@ -2,6 +2,9 @@
 
 import os
 import subprocess
+import sys
+import tempfile
+
 import pyisomd5sum
 
 # Pass in the rc, the expected value and the pass_all state
@@ -12,18 +15,35 @@ def pass_fail(rc, pass_value, pass_all):
     else:
         return ("FAIL", False)
 
+try:
+    iso_size = int(sys.argv[1])
+except (IndexError, ValueError):
+    # Default to 500K
+    iso_size = 500
 
-# create iso file
 try:
     # Python 3
     catch_error = FileNotFoundError
 except NameError:
     # Python 2
     catch_error = OSError
-try:
-    subprocess.check_call(["mkisofs", "-o", "testiso.iso", "."])
-except catch_error:
-    subprocess.check_call(["genisoimage", "-o", "testiso.iso", "."])
+
+# create iso file using a clean directory
+with tempfile.TemporaryDirectory(prefix="isomd5test-") as tmpdir:
+    # Write temporary data to iso test dir
+    with open(tmpdir+"/TEST-DATA", "w") as f:
+        # Write more data base on cmdline arg
+        for x in range(0,iso_size):
+            f.write("A" * 1024)
+
+    try:
+        subprocess.check_call(["mkisofs", "-o", "testiso.iso", tmpdir])
+    except catch_error:
+        subprocess.check_call(["genisoimage", "-o", "testiso.iso", tmpdir])
+
+    if not os.path.exists("testiso.iso"):
+        print("Error creating iso")
+        sys.exit(1)
 
 # implant it
 (rstr, pass_all) = pass_fail(pyisomd5sum.implantisomd5sum("testiso.iso", 1, 0), 0, True)
@@ -50,11 +70,11 @@ def callback(offset, total):
 
 def callback_abort(offset, total):
     print("    %s - %s" % (offset, total))
-    if offset > 500000:
+    if offset > 100000:
         return True
     return False
 
-print("Run with callback and abort after offset of 500000")
+print("Run with callback and abort after offset of 100000")
 (rstr, pass_all) = pass_fail(pyisomd5sum.checkisomd5sum("testiso.iso", callback_abort), 2, pass_all)
 print(rstr)