docs: clarify TESTS.md

TESTS.md

@@ -1,104 +1,12 @@
 # Automated tests
 
-TLDR: run `v test-all` locally, after making your changes,
+TLDR: do run `v test-all` locally, after making your changes,
 and before submitting PRs.
 
-## Notes
+Tip: use `v -cc tcc` when compiling tests, because TCC is much faster,
-In the `v` repo there are several different tests. The main types are:
+compared to most other C compilers like clang/gcc/msvc. Most test commands
-
+will use the V compiler and the V tools many times, potentially 
-* `_test.v` tests - check that `test_` functions succeed. These can be
+hundreds/thousands of times.
-run per directory or individually.
-* `.out` tests - run a `.vv` file and check the output matches the
-contents of the `.out` file with the same base name. This is
-particularly useful for checking that errors are printed.
-
-Tip: use `v -cc tcc` when compiling tests for speed.
-
-## `vlib/v/tests`
-
-General runnable tests for different features of the V compiler.
-
-* `vlib/v/tests/inout/compiler_test.v`
-
-Test output of running a V program matches an expected .out file.
-Check the source for how to test panics.
-
-* `vlib/v/gen/c/coutput_test.v`
-
-This tests whether the generated C source code matches all expectations,
-specified in *.c.must_have files, in the folder vlib/v/gen/c/testdata/ .
-
-Each `.c.must_have` file has to have a corresponding .vv file.
-
-Each `.c.must_have` file, consists of multiple lines. Each of these
-lines, *should* be present *at least once* in the output, when the .vv
-file is compiled with `-o -` .
-
-* `vlib/v/tests/run_project_folders_test.v`
-Tests whether whole project folders can be compiled, and run.
-NB: Each project in these folders, should finish with exit code 0,
-and it should output `OK` as its last stdout line.
-
-## Test building of actual V programs (examples, tools, V itself)
-
-* `v build-tools`
-* `v build-examples`
-* `v build-vbinaries`
-
-## vfmt tests
-
-In `vlib/v/fmt/` there are::
-
-* `v vlib/v/fmt/fmt_test.v`
-
-This checks `.out` tests.
-
-* `v vlib/v/fmt/fmt_keep_test.v`
-
-This verifies that `_keep.v` files would be unchanged by `vfmt -w`.
-
-* `v vlib/v/fmt/fmt_vlib_test.v`
-
-This checks all source files are formatted and prints a summary.
-This is not required.
-
-* `v test-fmt`
-
-Test all files in the current directory are formatted.
-
-## Markdown
-
-* `v check-md -hide-warnings .`
-
-Ensure that all .md files in the project are formatted properly,
-and that the V code block examples in them can be compiled/formatted too.
-
-## `.github/workflows/ci.yml`
-
-This runs various CI tests, e.g.:
-
-* `v vet vlib/v` - style checker
-* `v fmt -verify` on certain source files
-
-## `v test-cleancode`
-
-Check that most .v files, are invariant of `v fmt` runs.
-
-## `v test-self`
-
-Run `vlib` module tests, *including* the compiler tests.
-
-## `v vlib/v/compiler_errors_test.v`
-
-This runs tests for:
-* `vlib/v/checker/tests/*.vv`
-* `vlib/v/parser/tests/*.vv`
-
-### Special folders that compiler_errors_test.v will try to
-run/compile with specific options:
-
-vlib/v/checker/tests/globals_run/ - `-enable-globals run`; 
-results stored in `.run.out` files, matching the .vv ones.
 
 ## `v test-all`
 
@@ -113,3 +21,143 @@ It works, by running these in succession:
 * `v build-examples`
 * `v check-md -hide-warnings .`
 * `v install nedpals.args`
+
+# Details:
+In the `v` repo there are many tests. The main types are:
+
+## `_test.v` tests - these are the normal V test files.
+All `test_` functions in these files, will be ran automatically by 
+V's test framework.
+
+NB 1: You can run test files one by one, with:
+`v file_test.v` - this will run the test_ functions in file_test.v,
+and will exit with a 0 exit code, if they all had 0 failing assertions.
+
+`v -stats file_test.v` - this will run the test_ functions, and show a
+report about how much time it took to run each of them too.
+
+NB 2: You can also run many test files at once (in parallel, depending on
+how many cores you have), with:
+`v test folder` - this will run *all* `_test.v` files in `folder`,
+recursively.
+
+`v -stats test folder` - same, but will also produce timing reports
+about how fast each test_ function in each _test.v file ran.
+
+
+## `v test vlib/v/tests`:
+
+This folder contains _test.v files, testing the different features of the V
+compiler. Each of them will be compiled, and all the features in them have
+to work (verified by assertions).
+
+## `v vlib/v/tests/inout/compiler_test.v`
+
+This is a *test runner*, that checks whether the output of running a V program,
+matches an expected .out file. You can also check for code that does panic
+using this test runner - just paste the start of the `panic()` output in the
+corresponding .out file.
+
+NB: these tests, expect to find a pair of `.vv` and `.out` files, in the folder:
+vlib/v/tests/inout
+
+The test runner will run each `.vv` file, and will check that its output, matches
+the contents of the `.out` file with the same base name. This is particularly useful
+for checking that errors and panics are printed.
+
+## `v vlib/v/gen/c/coutput_test.v`
+
+coutput_test.v is a *test runner*, that checks whether the generated C source
+code matches *all* expectations, specified in *.c.must_have files, in the
+folder vlib/v/gen/c/testdata/ .
+
+Each `.c.must_have` file, *has* to have a corresponding `.vv` file.
+
+Each `.c.must_have` file, consists of multiple lines. Each of these
+lines, *should* be present *at least once* in the output, when the .vv
+file is compiled with `-o -` .
+
+## `v vlib/v/tests/run_project_folders_test.v`
+This *test runner*, checks whether whole project folders, can be compiled, and run.
+
+NB: Each project in these folders, should finish with an exit code of 0,
+and it should output `OK` as its last stdout line.
+
+## Test building of actual V programs (examples, tools, V itself)
+
+* `v build-tools`
+* `v build-examples`
+* `v build-vbinaries`
+
+## Formatting tests
+
+In `vlib/v/fmt/` there are:
+
+* `v vlib/v/fmt/fmt_test.v`
+
+This checks `.out` tests.
+
+* `v vlib/v/fmt/fmt_keep_test.v`
+
+This verifies that all `_keep.vv` files in the `vlib/v/fmt/tests/` folder,
+would be unchanged by `v fmt -w`, i.e. that the v source code formatter,
+generates a stable source output, that does not change, once it is already
+formatted once.
+
+* `v vlib/v/fmt/fmt_vlib_test.v`
+
+This checks that all V source files are formatted, and prints a summary.
+This is not required.
+
+* `v test-cleancode`
+
+Check that most .v files, are invariant of `v fmt` runs.
+
+* `v test-fmt`
+
+This tests that all .v files in the current folder are already formatted.
+It is useful for adding to CI jobs, to guarantee, that future contributions
+will keep the existing source nice and clean.
+
+## Markdown/documentation checks:
+
+* `v check-md -hide-warnings .`
+
+Ensure that all .md files in the project are formatted properly,
+and that the V code block examples in them can be compiled/formatted too.
+
+## `v test-self`
+
+Run `vlib` module tests, *including* the compiler tests.
+
+## `v vlib/v/compiler_errors_test.v`
+
+This runs tests for:
+* `vlib/v/scanner/tests/*.vv`
+* `vlib/v/checker/tests/*.vv`
+* `vlib/v/parser/tests/*.vv`
+
+NB: there are special folders, that compiler_errors_test.v will try to
+run/compile with specific options:
+
+vlib/v/checker/tests/globals_run/ - `-enable-globals run`; 
+results stored in `.run.out` files, matching the .vv ones.
+
+NB 2: in case you need to modify many .out files, run *twice* in a row:
+`VAUTOFIX=1 ./v vlib/v/compiler_errors_test.v` 
+This will fail the first time, but it will record the new output for each
+.vv file, and store it into the corresponding .out file. The second run
+should be now successfull, and so you can inspect the difference, and 
+commit the new .out files with minimum manual effort.
+
+NB 3: To run only some of the tests, use:
+`VTEST_ONLY=mismatch ./v vlib/v/compiler_errors_test.v`
+This will check only the .vv files, whose paths match the given filter.
+
+## `.github/workflows/ci.yml`
+
+This is a Github Actions configuration file, that runs various CI
+tests in the main V repository, for example:
+
+* `v vet vlib/v` - run a style checker.
+* `v test-self` (run self tests) in various compilation modes.