function assertASTDidntChange(beforeAST, afterAST) {
			if (!equal(beforeAST, afterAST)) {
				assert.fail("Rule should not modify AST.");
			}
		}
Check if the AST was changed
@param {ASTNode} beforeAST AST node before running
@param {ASTNode} afterAST AST node after running
@returns {void}
@private