+A. Add tests for orthogonality in the Peirce decomposition.
+
+B. Add support for a symmetric positive-definite bilinear form in
+ the JordanSpinEJA.
+
1. Add CartesianProductEJA.
2. Check the axioms in the constructor when check != False?
5. Factor out the unit-norm basis (and operator symmetry) tests once
all of the algebras pass.
+
+6. Can we make the minimal and characteristic polynomial tests work
+ for trivial algebras, too? Then we wouldn't need the "nontrivial"
+ argument to random_eja().
+
+7. Solve the charpoly system with A_of_x.solve_right(x_powers[r])
+ rather than dumbass Cramer's rule.