This test could possibly be made a bit more readable and robust by introducing a method `_getWFSURLQueryArgs` which returns a hash (we can assume that `Ext.urlEncode()` works as expected).  Then test each of the hash values, e.g.

    var queryArgs = filterPanel._getWFSURLQueryArgs(...)
    expect(queryArgs.a).toBe('b');
    expect(queryArgs.layerName).toBe(layerName);
    ....

`_makeWFSURL` does a little bit more (replaces 'wms' with 'wfs' etc), but you get the idea.