Finite test sets for morphisms which are square-free on some of Thue's square-free ternary words

Let S be one of ,bcb\ and , aca\, and let w be an infinite square-free word over Σ=,b,c\ with no factor in S. Suppose that f:Σ→ T^* is a non-erasing morphism. Word $f(w)$ is square-free if and only if f is square-free on factors of w of length 8 or less.