Function render_assertion 

pub fn render_assertion(
    out: &mut String,
    assertion: &Assertion,
    result_var: &str,
    module: &str,
    dep_name: &str,
    is_error_context: bool,
    unwrapped_fields: &[(String, String)],
    field_resolver: &FieldResolver,
    result_is_tree: bool,
    result_is_simple: bool,
    result_is_vec: bool,
    result_is_option: bool,
    returns_result: bool,
)

Render a single assertion into the test function body.