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Terminal::Tests - Terminal emulator, multiplexer, and font quality tests


$ terminal-quick-test [--ruler]
# ... single-page test output ...

$ terminal-test
# ... multi-page survey-style test ...


Terminal::Tests is a collection of quality and correctness tests for terminal emulators, terminal multiplexers, Unicode configurations, and monospace fonts.

The simple terminal-quick-test program displays a simple test pattern that should fit in a default 80x24 terminal window, and will catch some of the most common terminal configuration problems. For a more nuanced test, try the full terminal-test program, which shows numerous test patterns and describes what you should expect to see in each.

Quick Test Pattern

To display the quick test program, simply run terminal-quick-test; you can add the --ruler option if you'd like to also display a screen width ruler to help detect misalignment. Correct output should be no more than 79 columns on any line, so you've likely run into a terminal bug if the displayed test pattern is wider than that.

At the time of writing, I've not yet seen any terminals show a perfect test pattern; the best results so far get everything except the emoji row correct. For reference, here's what the pattern looks like on a default gnome-terminal in Ubuntu 22.04 LTS or Linux Mint 21.x (based on that same Ubuntu LTS release):

Screenshot of quick test on default gnome-terminal

The rightmost block of emoji should have skin tones applied, rather than shown in fallback mode as a tone swatch next to a yellow emoji, causing the line to overflow. Windows Terminal in Windows 10 similarly gets most of the pattern correct, but again fails on the emoji row:

Screenshot of quick test on Windows Terminal in UTF-8 mode

Here it applies skin tones to the rightmost set, but still leaves extra room where the tone swatch would be, thus once again causing the line to be too long -- and this time also failing on the leftmost set of emoji faces, which should display in text outline mode as seen in the screenshot for gnome-terminal.

However, Windows Terminal will only do that well under Windows 10 if "beta" UTF-8 support is turned on (see separate [Windows 10](#Windows 10) section below). Without that, the test pattern will fall apart:

Screenshot of quick test on Windows Terminal in UTF-16 mode

Some failures are more subtle, affecting only one or two features. Here's an example of the pattern as seen inside of GNU Screen in a gnome-terminal:

Screenshot of quick test running inside GNU Screen on gnome-terminal

There are two degradations here. The first is that GNU Screen supports 4-bit and 8-bit ANSI color, but not 24-bit ANSI color, so the red/green/blue bars in the top middle are missing. The second is that GNU Screen has replaced the italic attribute with inverse at the top left.

Operating system and terminal software versions can make a significant difference. For example, here's Terminal on macOS 10.14:

Screenshot of quick test running on Terminal on macOS 10.14

There's a massive improvement moving to Terminal on macOS 12.6:

Screenshot of quick test running on Terminal on macOS 12.6

And another overall quality improvement switching to iTerm2 on the same macOS version (12.6):

Screenshot of quick test running on iTerm2 on macOS 12.6

iTerm2 isn't purely an improvement over Terminal; there are a few minor degradations as well, such as shaded blocks being the wrong size, dashed lines being offset vertically, square corners being lengthened, and some text symbols gaining unrequested color.

Finally, some problems are merely configuration or option issues. Here's xterm in its default configuration on my Linux system, using the low-res (but at least somewhat Unicode-capable) bitmap "fixed" font, launched with just xterm:

Screenshot of quick test running on xterm using the Unicode fixed font

Many of the symbols are nearly unreadable, many of the advanced drawing characters are missing, and emoji aren't supported at all. Even worse, specifying a larger bitmap font size defaults to using the non-Unicode version of the font, here launched with xterm -fn 10x20:

Screenshot of quick test running on xterm using the Latin-1 fixed font

Using a scalable font will work better, even at the default small size, but color emoji are still unsupported (only text outlines are shown), and many of the advanced drawing characters are misaligned or cut off. Here I've just told xterm to use the default system monospace scalable font using xterm -fa mono:

Screenshot of quick test running on xterm using the mono scalable font

Unsurprisingly the scalable font scales up better too (using xterm -fa mono -fs 12):

Screenshot of quick test running on xterm using the mono scalable font at 12-point size

Full Terminal Test

The terminal-test program includes a far more complete set of test patterns across a range of categories, including descriptions of what you should expect to see in each pattern, as well as common artifacts that you should ideally not see. You can rate the display of each pattern on a simple scale, and the program will summarize the results in text or JSON (with the --json option) after you have rated the last test pattern.

Terminal-Specific Tweaks

Windows 10

By default Windows Terminal under Windows 10 supports only UTF-16, an old Unicode encoding that has otherwise been replaced by the UTF-8 encoding. To fix this, you'll need to follow the instructions in the Enable UTF-8 in Windows Terminal gist, kindly provided by sapeurfaire.


Geoffrey Broadwell gjb@sonic.net


Copyright © 2022-2023 Geoffrey Broadwell

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.