diff --git a/tests/README.md b/tests/README.md
new file mode 100644
index 000000000..56c9223b9
--- /dev/null
+++ b/tests/README.md
@@ -0,0 +1,58 @@
+# Tests for LVGL
+
+The tests in the folder can be run locally and automatically by GitHub CI.
+
+## Running locally
+
+### Requirements (Linux)
+1. Be sure GCC and Python3 is installed.
+2. Install [gcovr](https://gcovr.com/en/stable/index.html) with `pip install gcovr`
+3. Install Ruby with `sudo apt-get install ruby-full`
+
+### Run test
+1. Enter `lvgl/tests/`
+2. Run the tests with `./main.py [OPTIONS]`. The options are
+  - `report` Create a html page in the `report` folder with the coverage report.
+  - `test` Build and run only test. Without this option LVGL will be built with various configurations.
+  - `noclean` Do not clean the project before building. Useful while writing test to save some times. 
+
+For example: 
+- `./main.py` Run all the test as they run in the CI.
+- `./main.py report test noclean` Run only the test, should be sued when writing tests.
+
+
+## Running automatically
+TODO
+
+GitHub's CI automatically runs these tests on pushes and pull requests to `master` and `releasev8.*` branches. 
+
+## Directory structure
+- `src` Source files of the tests
+    - `test_cases` The written tests,
+    - `test_runners` Generated automatically from the files in `test_cases`.
+    - other miscellaneous files and folders 
+- `ref_imgs` - Reference images for screenshot compare
+- `report` - Coverage report. Generated if the `report` flag was passed to `./main.py` 
+- `unity` Source files of the test engine
+
+## Add new tests
+
+### Create new test file
+New test needs to be added into the `src/test_cases` folder. The name of the files should look like `test_<name>.c`. The the basic skeleton of a test file copy `_test_template.c`.
+
+### Asserts
+See the list of asserts [here](https://github.com/ThrowTheSwitch/Unity/blob/master/docs/UnityAssertionsReference.md).
+
+There are some custom, LVGL specific asserts:
+- `TEST_ASSERT_EQUAL_SCREENSHOT("image1.png")` Render the active screen and compare its content with an image in the `ref_imgs` folder. 
+If the compare fails `lvgl/test_screenshot_error.h` is created with the content of the frame buffer as an image. 
+To see the that image `#include "test_screenshot_error.h"` and call `test_screenshot_error_show();`.
+- `TEST_ASSERT_EQUAL_COLOR(color1, color2)` Compare two colors.
+
+### Adding new reference images
+The reference images can be taken by copy-pasting the test code in to LVGL simulator and saving the screen. 
+LVGL needs to
+- 800x480 resolution
+- 32 bit color depth
+- `LV_USE_PERF_MONITOR` and `LV_USE_MEM_MONITOR` disabled
+- use the default theme, with the default color (don't set a theme manually)
diff --git a/tests/unity/unity_support.c b/tests/unity/unity_support.c
index eab620901..cceefba14 100644
--- a/tests/unity/unity_support.c
+++ b/tests/unity/unity_support.c
@@ -117,9 +117,9 @@ bool lv_test_assert_img_eq(const char * fn_ref)
       memcpy(&act_px, ptr_act, 3);
       TEST_PRINTF("Diff in %s at (%d;%d), %x instead of %x)", fn_ref, x, y, act_px, ref_px);
       
-      FILE * f = fopen("../image_err.h", "w");
+      FILE * f = fopen("../test_screenshot_error.h", "w");
       
-      fprintf(f, "static const uint32_t img_data[] = {\n");
+      fprintf(f, "static const uint32_t test_screenshot_error_data[] = {\n");
       
       i_buf = 0;
       for (y = 0; y < 480; y++) {
@@ -134,17 +134,17 @@ bool lv_test_assert_img_eq(const char * fn_ref)
       }
       fprintf(f, "};\n\n");
       
-      fprintf(f, "static lv_img_dsc_t dsc = { \n"
+      fprintf(f, "static lv_img_dsc_t test_screenshot_error_dsc = { \n"
       "  .header.w = 800,\n"
       "  .header.h = 480,\n"
       "  .header.always_zero = 0,\n"
       "  .header.cf = LV_IMG_CF_TRUE_COLOR,\n"
       "  .data_size = 800 * 480 * 4,\n"
-      "  .data = img_data};\n\n"
-      "static inline void show_test_img_error(void)\n"
+      "  .data = test_screenshot_error_data};\n\n"
+      "static inline void test_screenshot_error_show(void)\n"
       "{\n"
       "  lv_obj_t * img = lv_img_create(lv_scr_act());\n"
-      "  lv_img_set_src(img, &dsc);\n"
+      "  lv_img_set_src(img, &test_screenshot_error_dsc);\n"
       "}\n");
       
       fclose(f);