How can I verify a SVG doc is correct? (version 1.2)

There is a python utility in terminal svgcheck, which claims to target version 1.2, as defined in draft-7996-bis. A promising utility, IMHO.

SVG Checking Procedure.

pip install svgcheck

svgcheck ~/path/to/mysvgfile.svg

The svg file with proper standards will give something like:

$ svgcheck alert-circle.svg
Parsing file alert-circle.svg
INFO: File conforms to SVG requirements.

• Make sure you have pip installed and python configured properly

You can use e.g http://validator.nu. Since your file is standalone, select xml parsing, paste the RNG url in the schema textfield (the schema url you're looking can be found in the relevant specification, in this case SVG 1.2 Tiny: http://www.w3.org/TR/SVGTiny12/relaxng/Tiny-1.2.rng ).

Even your three line snippet isn't valid SVG 1.2 Tiny content (x and y attributes are not allowed on the <svg> element in Tiny). You should add a link to your file somewhere, otherwise it's hard to say what it should look like.