diff --git a/capywfa/capywfa.py b/capywfa/capywfa.py
index 3f8d50d..7d7b85b 100755
--- a/capywfa/capywfa.py
+++ b/capywfa/capywfa.py
@@ -7,6 +7,7 @@
 # SPDX-License-Identifier: MIT
 
 import argparse
+import glob
 import textwrap
 import sys
 import os
@@ -107,11 +108,30 @@ def pass1_map_bom(bom, sw360_url, sw360_token):
     return result
 
 
-def pass3_download_sources(bom):
+def pass3_download_sources(bom, pkg_dir):
     for item in bom.components:
-        if not (get_cdx(item, "MapResult") == MapResult.NO_MATCH
-                or (MapBom.is_good_match(get_cdx(item, "MapResult"))
-                    and get_cdx(item, "Sw360SourceFileCheck") != "passed")):
+        map_result = get_cdx(item, "MapResult")
+        is_missing_from_sw360 = map_result == MapResult.NO_MATCH
+        is_in_sw360_but_unverified = (
+            MapBom.is_good_match(map_result)
+            and get_cdx(item, "Sw360SourceFileCheck") != "passed"
+        )
+        needs_download = is_missing_from_sw360 or is_in_sw360_but_unverified
+
+        if needs_download and pkg_dir:
+            package_name = item.purl.name
+            version = item.version.removesuffix(".debian")
+            version = version.split(":", 1)[-1]  # Remove epoch if present
+            pattern = f"{package_name}_{version}*"
+            matches = glob.glob(os.path.join(pkg_dir, pattern))
+            if matches:
+                set_cdx(item, "SourceFileComment", "sources locally available")
+                print(
+                    f"Found local source for {item.name} {item.version}: "
+                    f"{os.path.basename(matches[0])}"
+                )
+
+        if not needs_download:
             set_cdx(item, "SourceFileDownload", "skip")
     return bom
 
@@ -352,7 +372,7 @@ def main():
     print("== Pass 3: Download missing and unchecked sources ==")
     print()
 
-    bom = pass3_download_sources(bom)
+    bom = pass3_download_sources(bom, args.sources)
     outputbom = write_bom(bom, filename+"-3-download"+extension)
     missing_source_count = len(
         [item for item in bom.components
diff --git a/capywfa/lst_to_sbom.py b/capywfa/lst_to_sbom.py
index e0e645b..789645a 100644
--- a/capywfa/lst_to_sbom.py
+++ b/capywfa/lst_to_sbom.py
@@ -171,6 +171,8 @@ def main():
 
     bom = lst_to_sbom(format=args.format, package_list=args.package_list)
 
+    if os.path.exists(args.output_file):
+        os.remove(args.output_file)
     JsonV1Dot6(bom=bom).output_to_file(args.output_file, indent=2)
     print(f"SBOM written to {args.output_file}")
 
diff --git a/test/test_capywfa.py b/test/test_capywfa.py
new file mode 100644
index 0000000..adc4394
--- /dev/null
+++ b/test/test_capywfa.py
@@ -0,0 +1,83 @@
+# SPDX-FileCopyrightText: 2026 Siemens
+# SPDX-License-Identifier: MIT
+
+import os
+import tempfile
+
+from cyclonedx.model.bom import Bom
+from cyclonedx.model.component import Component, ComponentType
+from packageurl import PackageURL
+
+from capywfa.capywfa import pass3_download_sources, MapResult
+from capywfa.cdx_support import set_cdx, get_cdx
+
+
+def create_test_component(name, version, map_result=None, source_check=None):
+    """Helper function to create a test component with CDX properties."""
+    component = Component(
+        name=name,
+        type=ComponentType.LIBRARY,
+        version=version,
+        purl=PackageURL("deb", "debian", name, version, {"arch": "source"})
+    )
+    if map_result is not None:
+        set_cdx(component, "MapResult", map_result)
+    if source_check is not None:
+        set_cdx(component, "Sw360SourceFileCheck", source_check)
+    return component
+
+
+def test_pass3_download_sources_no_pkg_dir():
+    """Test that pass3_download_sources works when no package directory is provided."""
+    bom = Bom(components=[
+        create_test_component("testpkg", "1.0-1", MapResult.NO_MATCH)
+    ])
+    result = pass3_download_sources(bom, None)
+    assert result == bom
+    # Should not set SourceFileComment when pkg_dir is None
+    assert not get_cdx(bom.components[0], "SourceFileComment")
+
+
+def test_pass3_download_sources_local_package_found():
+    """Test that local packages are detected and marked as available."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        test_file = os.path.join(tmpdir, "testpkg_1.0-1.dsc")
+        with open(test_file, "w") as f:
+            f.write("test")
+
+        bom = Bom(components=[
+            create_test_component("testpkg", "1.0-1", MapResult.NO_MATCH)
+        ])
+
+        result = pass3_download_sources(bom, tmpdir)
+
+        assert get_cdx(result.components[0], "SourceFileComment") == "sources locally available"
+
+
+def test_pass3_download_sources_local_package_not_found():
+    """Test that packages are not marked when local files don't exist."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        bom = Bom(components=[
+            create_test_component("testpkg", "1.0-1", MapResult.NO_MATCH)
+        ])
+
+        result = pass3_download_sources(bom, tmpdir)
+
+        # Should not set SourceFileComment when no matching file found
+        assert not get_cdx(result.components[0], "SourceFileComment")
+
+
+def test_pass3_download_sources_version_with_epoch():
+    """Test that version with epoch is handled correctly."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        test_file = os.path.join(tmpdir, "testpkg_1.0-1.dsc")
+        with open(test_file, "w") as f:
+            f.write("test")
+
+        # Component has epoch in version
+        bom = Bom(components=[
+            create_test_component("testpkg", "2:1.0-1", MapResult.NO_MATCH)
+        ])
+
+        result = pass3_download_sources(bom, tmpdir)
+        assert get_cdx(result.components[0], "SourceFileComment") == "sources locally available"