UI Testing

The XML test module is a powerful and flexible way to define functional UI tests.

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Overview

The XML test module is a powerful and flexible way to define functional UI tests.

Test XML files are similar to components but are wrapped in a <test> tag and consist of two main parts:

UI Definition: Use <styles>, <consts>, and <view> to define how the UI should look. This is identical to how <component>s are structured.
Test Steps: Encapsulated in a <steps> tag, these define the actions and assertions for the test.

Step Types

The following step types are currently supported (with example parameters):

<move_to x="10" y="30"/>: Move the mouse to the specified screen coordinates.
<click_at x="10" y="30"/>: Simulates a click at the specified screen coordinates.
<press/>: Press on the current screen coordinate.
<release/>: Release on the current screen coordinate.
<wait ms="100"/>: Waits for the given number of milliseconds. LVGL continues running, including animations and timers.
<freeze ms="100"/>: Pauses the UI and LVGL's internal time. Useful for visual debugging.
<subject_set subject="subject1" value="5> Set an integer or string subject's value.
<subject_compare subject="subject1" value="10"> Compare an integer or strings subject's value against a reference value.
`: Compares the current screen with a reference image.
- If the image doesn't exist, it is created.
- If the comparison fails, an image with err` suffix is saved for inspection.

Example:

xml

<test width="300" height="400">
    <view width="100%" height="100%" flex_flow="column">
        <lv_checkbox text="First one!"/>
        <lv_slider />
    </view>

    <steps>
        <screenshot_compare path="imgs/before.png"/>
        <click_at x="32" y="32"/>
        <subject_compare subject="subject2" value="50"/>
        <click_at x="50" y="64"/>
        <subject_set subject="subject2" value="10"/>
        <wait ms="300"/>
        <screenshot_compare path="imgs/after.png"/>
    </steps>
</test>

Registering Tests

Tests can be registered in two ways:

From file: lv_xml_test_register_from_file("path/to/test.xml", "A:ref_images")
From string: lv_xml_test_register_from_data(xml_data, "A:ref_images")

The second parameter specifies a prefix for screenshot comparison paths.

To unregister tests, use:

lv_xml_test_unregister

This is called automatically when registering a new test, so manual calls are usually unnecessary.

Running Tests

All steps

To execute the registered test, use lv_xml_test_run_all(slowdown).

It will clean the screen and create a fresh instance of the view to be tested.

The slowdown parameter controls playback speed:

0: Maximum speed
1: Real-time speed
2: Half-speed
10: 10× slower
...and so on

lv_xml_test_run_all() blocks until all steps are completed. It is safe to call it multiple times.

The return value is the number of failed tests.

Step-by-step

It's also possible to run each step separately, one after another.

First, call lv_xml_test_run_init to prepare for executing the steps. It will clean the screen and create a fresh instance of the view to be tested.

Get the number of steps using lv_xml_test_get_step_count and then call lv_xml_test_run_next(slowdown) as many times.

lv_xml_test_run_next returns true if the given step passed, or false if it failed.

Finally, call lv_xml_test_run_stop to clean up and exit testing mode.

Getting the Test Results

Currently, only screenshot_compare steps can fail. However, the result of each step can be queried:

uint32_t step_cnt = lv_xml_test_get_step_count();
for(uint32_t i = 0; i < step_cnt; i++) {
    if(lv_xml_test_get_step_type(i) == LV_XML_TEST_STEP_TYPE_SCREENSHOT_COMPARE) {
        if(lv_xml_test_get_status(i))
            printf("Step %d passed\n", i);
        else
            printf("Step %d failed\n", i);
    } else {
        printf("Step %d is not a screenshot comparison\n", i);
    }
}