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.