ext2fs_open2: The ext2 superblock is corrupt
../e2fsck/e2fsck: Superblock invalid, trying backup blocks...
../e2fsck/e2fsck: The ext2 superblock is corrupt while trying to open test.img
../e2fsck/e2fsck: Trying to load superblock despite errors...
ext2fs_open2: The ext2 superblock is corrupt
../e2fsck/e2fsck: Superblock invalid, trying backup blocks...
../e2fsck/e2fsck: The ext2 superblock is corrupt while trying to open test.img

The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem.  If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
 or
    e2fsck -b 32768 <device>

Exit status is 8