extmod/vfs_posix: Additional tests for coverage of error cases.

Signed-off-by: Christian Walther <cwalther@gmx.ch>

tests/extmod/vfs_posix_enoent.py

@@ -0,0 +1,42 @@
+# Test for VfsPosix error conditions
+
+try:
+    import os
+    import sys
+
+    os.VfsPosix
+except (ImportError, AttributeError):
+    print("SKIP")
+    raise SystemExit
+
+if sys.platform == "win32":
+    # Windows doesn't let you delete the current directory, so this cannot be
+    # tested.
+    print("SKIP")
+    raise SystemExit
+
+# We need an empty directory for testing.
+# Skip the test if it already exists.
+temp_dir = "vfs_posix_enoent_test_dir"
+try:
+    os.stat(temp_dir)
+    print("SKIP")
+    raise SystemExit
+except OSError:
+    pass
+
+curdir = os.getcwd()
+os.mkdir(temp_dir)
+os.chdir(temp_dir)
+os.rmdir(curdir + "/" + temp_dir)
+try:
+    print("getcwd():", os.getcwd())
+except OSError as e:
+    # expecting ENOENT = 2
+    print("getcwd():", repr(e))
+
+try:
+    print("VfsPosix():", os.VfsPosix("something"))
+except OSError as e:
+    # expecting ENOENT = 2
+    print("VfsPosix():", repr(e))

tests/extmod/vfs_posix_enoent.py.exp

@@ -0,0 +1,2 @@
+getcwd(): OSError(2,)
+VfsPosix(): OSError(2,)