First test

zig build test

zig test src/term_tests.zig

We want to test if our functions work. Specifically, we'll test the getWindowSize() and getCursorPosition(), which also test setting raw mode and readChars() along the way.

We'll add a couple of constants at the bottom of ansi.zig:

const builtin = @import("builtin");

// CSI sequence to clear the screen.
pub const ClearScreen = CSI ++ "2J" ++ CSI ++ "H";

We'll create a new file named src/term_tests.zig, with this content:

//! Additional tests that need an interactive terminal, not testable with:
//!
//!     zig build test
//!
//! Must be tested with:
//!
//!     zig test src/term_tests.zig

test "getWindowSize" {
    const orig_termios = try linux.enableRawMode();
    defer linux.disableRawMode(orig_termios);

    const s1 = try ansi.getWindowSize();
    try std.testing.expect(s1.rows > 0 and s1.cols > 0);
    const s2 = try ansi.getCursorPosition();
    try linux.write(ansi.ClearScreen);
    try std.testing.expect(s1.rows == s2.rows and s1.cols == s2.cols);
}

const std = @import("std");
const linux = @import("linux.zig");
const ansi = @import("ansi.zig");

We'll clear the screen after having called the second method, because that function call has the side-effect of maximizing the terminal screen, which messes up the output of the test result.

To ensure that our getWindowSize() works and doesn't fallback, we must add a check in that function:

    if (linux.winsize(&wsz) == -1 or wsz.col == 0) {

        if (builtin.is_test) return error.getWindowSizeFailed;

This will cause the function to error out, if the ioctl method fails. We will then get the window size with the fallback method, and ensure the resulting sizes are the same.