tests/extmod/vfs_fat: Improve VFS test coverage.

Covered case:
- Stat cases
- Invalid read/write/flush/close
- Invalid mkdir/rmdir/remove/getcwd
- File seek/tell, modes a/x/+, t/b
- Writing to a full disk
- Full path rename, slash trim
- Rename cases
- Bytestring listdir
- File object printing

1 files changed, 160 insertions, 0 deletions

diff --git a/tests/extmod/vfs_fat_fileio.py b/tests/extmod/vfs_fat_fileio.py
new file mode 100644
index 0000000000..26fec78281
--- /dev/null
+++ b/tests/extmod/vfs_fat_fileio.py
@@ -0,0 +1,160 @@
+import sys
+import uos
+import uerrno
+try:
+    uos.VfsFat
+except AttributeError:
+    print("SKIP")
+    sys.exit()
+
+
+class RAMFS:
+
+    SEC_SIZE = 512
+
+    def __init__(self, blocks):
+        self.data = bytearray(blocks * self.SEC_SIZE)
+
+    def readblocks(self, n, buf):
+        #print("readblocks(%s, %x(%d))" % (n, id(buf), len(buf)))
+        for i in range(len(buf)):
+            buf[i] = self.data[n * self.SEC_SIZE + i]
+
+    def writeblocks(self, n, buf):
+        #print("writeblocks(%s, %x)" % (n, id(buf)))
+        for i in range(len(buf)):
+            self.data[n * self.SEC_SIZE + i] = buf[i]
+
+    def ioctl(self, op, arg):
+        #print("ioctl(%d, %r)" % (op, arg))
+        if op == 4:  # BP_IOCTL_SEC_COUNT
+            return len(self.data) // self.SEC_SIZE
+        if op == 5:  # BP_IOCTL_SEC_SIZE
+            return self.SEC_SIZE
+
+
+try:
+    bdev = RAMFS(48)
+except MemoryError:
+    print("SKIP")
+    sys.exit()
+
+uos.VfsFat.mkfs(bdev)
+vfs = uos.VfsFat(bdev, "/ramdisk")
+
+# file IO
+f = vfs.open("foo_file.txt", "w")
+print(str(f)[:17], str(f)[-1:])
+f.write("hello!")
+f.flush()
+f.close()
+try:
+    f.write("world!")
+except OSError as e:
+    print(e.args[0] == uerrno.EINVAL)
+
+try:
+    f.read()
+except OSError as e:
+    print(e.args[0] == uerrno.EINVAL)
+
+try:
+    f.flush()
+except OSError as e:
+    print(e.args[0] == uerrno.EINVAL)
+
+try:
+    f.close()
+except OSError as e:
+    print(e.args[0] == uerrno.EINVAL)
+
+try:
+    vfs.open("foo_file.txt", "x")
+except OSError as e:
+    print(e.args[0] == uerrno.EEXIST)
+
+with vfs.open("foo_file.txt", "a") as f:
+    f.write("world!")
+
+with vfs.open("foo_file.txt") as f2:
+    print(f2.read())
+    print(f2.tell())
+
+    f2.seek(0, 0) # SEEK_SET
+    print(f2.read(1))
+
+    f2.seek(0, 1) # SEEK_CUR
+    print(f2.read(1))
+    try:
+        f2.seek(1, 1) # SEEK_END
+    except OSError as e:
+        print(e.args[0] == uerrno.EOPNOTSUPP)
+
+    f2.seek(-2, 2) # SEEK_END
+    print(f2.read(1))
+
+# dirs
+vfs.mkdir("foo_dir")
+
+try:
+    vfs.rmdir("foo_file.txt")
+except OSError as e:
+    print(e.args[0] == 20) # uerrno.ENOTDIR
+
+try:
+    vfs.mkdir("foo_dir")
+except OSError as e:
+    print(e.args[0] == uerrno.EEXIST)
+
+try:
+    vfs.remove("foo_dir")
+except OSError as e:
+    print(e.args[0] == uerrno.EISDIR)
+
+try:
+    vfs.remove("no_file.txt")
+except OSError as e:
+    print(e.args[0] == uerrno.ENOENT)
+
+try:
+    vfs.rename("foo_dir", "/null")
+except OSError as e:
+    print(e.args[0] == uerrno.ENODEV)
+
+# file in dir
+with vfs.open("foo_dir/file-in-dir.txt", "w+t") as f:
+    f.write("data in file")
+
+with vfs.open("foo_dir/file-in-dir.txt", "r+b") as f:
+    print(f.read())
+
+with vfs.open("foo_dir/sub_file.txt", "w") as f:
+    f.write("subdir file")
+
+# directory not empty
+try:
+    vfs.rmdir("foo_dir")
+except OSError as e:
+    print(e.args[0] == uerrno.EACCES)
+
+# trim full path
+vfs.rename("foo_dir/file-in-dir.txt", "/ramdisk/foo_dir/file.txt")
+print(vfs.listdir("foo_dir"))
+
+vfs.rename("foo_dir/file.txt", "moved-to-root.txt")
+print(vfs.listdir())
+
+# valid removes
+vfs.remove("foo_dir/sub_file.txt")
+vfs.remove("foo_file.txt")
+vfs.rmdir("foo_dir")
+print(vfs.listdir())
+
+# disk full
+try:
+    bsize = vfs.statvfs("/ramdisk")[0]
+    free = vfs.statvfs("/ramdisk")[2] + 1
+    f = vfs.open("large_file.txt", "wb")
+    f.write(bytearray(bsize * free))
+except OSError as e:
+    print("ENOSPC:", e.args[0] == 28) # uerrno.ENOSPC