tests: extended test case for Manifest.from_file()

Manifest.from_file() and Manifest.from_file(topdir=<topdir>) produces
different results.

The commit extends the test case to verify that creation of Manifest
object is identical when produced with topdir argument or without, as
long as the topdir provided as argument is identical to what
`util.west_topdir()` would have returned.

Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>

tests/test_manifest.py

@@ -1051,12 +1051,21 @@ def test_as_dict_and_yaml(manifest_repo):
     for p in frozen_expected['manifest']['projects']:
         p['revision'] = fake_sha
 
+    # Manifest.from_file() and Manifest.from_file(topdir=<topdir>) shall
+    # produce result when given topdir is identical to what util.west_topdir()
+    # produces.
     manifest = MF()
 
+    manifest_topdir = MF(topdir=os.path.dirname(manifest_repo))
+
     # We can always call as_dict() and as_yaml(), regardless of what's
     # cloned.
 
     as_dict = manifest.as_dict()
+
+    as_dict_topdir = manifest_topdir.as_dict()
+    assert as_dict == as_dict_topdir
+
     yaml_roundtrip = yaml.safe_load(manifest.as_yaml())
     assert as_dict == content_dict
     assert yaml_roundtrip == content_dict