let todo_desc = "TODO description";

// Test that a value is true.
let ok = module{
    // test value expected to be true for success.
    test=false,
    // descriptive message to use in output.
    desc=todo_desc,
} => ({ok=ok, desc=desc}) {
    (mod.desc != NULL) || fail "description can't be null";

    let ok = mod.test;
    let desc = "@" % (mod.desc);
};

// Test that a value is not true.
let not_ok = module{
    // Test value expected to to be false for success.
    test=true,
    // descriptive message to use in output.
    desc=todo_desc,
} => ({ok=ok, desc=desc}) {
    (mod.desc != NULL) || fail "description can't be null";

    let ok = not mod.test;
    let desc = "@" % (mod.desc);

};

// Asserts that two values are equal. Does deep equal comparisons.
let equal = module{
    // Left value for deep equal comparison.
    left=NULL,
    // right value for deep equal comparison.
    right=NULL,
    desc="",
} => ({ok=ok, desc=desc}) {
    (mod.desc != NULL) || fail "description can't be null";

    let ok = mod.left == mod.right;
    let desc = select ((mod.desc == ""), "@ == @" % (mod.left, mod.right)) => {
        false = mod.desc,
    };
};

// Asserts that two values are not equal. Does deep equal comparisons.
let not_equal = module{
    // Left value for deep equal comparison.
    left=NULL,
    // right value for deep equal comparison.
    right=NULL,
    desc="",
} => ({ok=ok, desc=desc}) {
    (mod.desc != NULL) || fail "description can't be null";

    let ok = mod.left != mod.right;
    let desc = select ((mod.desc == ""), "@ != @" % (mod.left, mod.right)) => {
        false = mod.desc,
    };
};